Mammalia

MAMMALIA

MAMMALIA (French, Mammifères ; German, Säuge- thiere) is the name invented by Linnaeus (from the Latin, mamma), and now commonly used by zoologists, for one of the classes of vertebrated animals, which, though the best known and undoubtedly the most important group of the animal kingdom, has never received any generally accepted vernacular designation in our language. The unity of structure of the animals composing this class, and their definite demarcation from other vertebrates, were not recognized until comparatively modern times, and hence no word was thought of to designate what zoologists now term a mammal. The nearest equivalents in common use are “beast” and “quadruped,’’ both of which, however, cover a different ground, as they are often used to include the larger four-footed reptiles, and to exclude certain undoubted mammals, as Man, Bats, and Whales.

The limits of the class as now understood by zoologists are perfectly well defined, and, although certain forms still existing on the earth (though not those mentioned above as excluded by the popular idea) are of exceedingly aberrant structure, exhibiting several well-marked characters which connect them with the lower vertebrated groups, common consent retains them in the class with which the great proportion of their characters ally them, and hitherto no traces of any species showing still more divergent or transitional characters have been discovered. There is thus a great interval, not bridged over by any known forms, recent or extinct, between mammals and other vertebrates.

In the gradual order of evolution of living beings, mammals taken altogether are certainly the highest in organization, as they were probably the last to appear on the earth’s surface, though this must be said with some reservation, pending further knowledge of the early history of the class of birds. But, as in speaking of all other large and greatly differentiated groups, this expression must not be understood in too limited a sense. The tendency to gradual perfection for their particular station in life, which all groups manifest, leads to various lines of specialization, or divergence from the common or general type, which may or may not take the direction of elevation. A too complex and sensitive condition of organization may in some circumstances of life be disadvantageous, and modification may then take place in a retrograde direction. In mammals, as in other classes, there are low forms as well as high forms, but by any tests that can be applied, especially those based on the state of development of the central nervous system, it will be seen that the average exceeds the average of any other class, that many species of this class far excel those of any other in perfection of structure, and that it contains one form which is unquestionably the culminating point yet arrived at amongst organized beings.

With regard to the time of the first appearance of mammals upon the earth, the geological record is provokingly imperfect. At the commencement of the Tertiary period they were abundant, and already modified into most of the leading types at present existing. It was at one time thought that they first came into being at this date, but the discovery of fragments of numerous small species has revealed the existence of some forms of the class at various periods throughout almost the whole of the age of the deposition of the Secondary rocks. This subject will be reverted to later on.

It hardly need be said that mammals are vertebrated animals, and possess all the characteristics common to the members of that division of the animal kingdom. They are separated from the Ichthyopsida (fishes and amphibia) and agree with the Sauropsida (reptiles and birds) in the possession during their development of an amnion and allantois, and in never having external branchiae or gills. They differ from reptiles and resemble birds in being warm-blooded, and having a heart with four cavities and a complete double circulation. They differ from both birds and reptiles in the red corpuscles of the blood being nucleated and, with very few exceptions, circular in outline; in the lungs being freely suspended in a thoracic cavity, separated from the abdomen by a complete muscular partition, the diaphragm, which is the principal agent in inflating the lungs in respiration; in having but one aortic arch, which curves over the left bronchus; in the skin being more or less clothed with hair, and never with feathers; in the greater perfection of the commissural system of the cerebral hemispheres, which has either a complete corpus callosum, or an incomplete one associated with a very larger anterior commissure; in having no syrinx or inferior vocal organ, but a complete larynx at the upper end of the trachea; in having a mandible of which each ramus (except in very early developmental conditions) consists of a single bone on each side, articulating to the squamosal, without the intervention of a quadrate bone; in having a pair of laterally placed occipital condyles instead of one median one; and in the very obvious character of the female being provided with mammary glands, by the secretion of which the young (produced alive and not by means of externally hatched eggs) are nourished for some time after birth.

In common with all vertebrated animals, mammals have never more than two pairs of limbs. In the great majority of the class both are well-developed and functional, and adapted for terrestrial progression, as the larger number of mammals live ordinarily on the surface of the earth. They are, however, by no means limited to this situation. Some species spend the greater part of their lives beneath the surface, their fore limbs being specially modified for burrowing; others are habitually arboreal, their limbs being fitted for climbing or hanging to boughs of trees; some are as aerial as birds, the fore limbs being developed into wings of a special character; others are as aquatic as fishes, the limbs assuming the form of fins or paddles. In many of the latter the hinder extremities are either completely suppressed, or present only in a rudimentary state. In no known mammal are the fore limbs absent.

The hinder extremity of the axis of the body is usually prolonged into a tail, which may be a mere pendent appendage, or modified to perform various functions, as grasping boughs in climbing, or even gathering food, in the case of the prehensile-tailed Monkeys and Opossums, swimming in the Cetacea, and acting as a flap to drive away troublesome insects from the skin in the Ungulata.

GENERAL ANATOMICAL CHARACTERS OF THE MAMMALIA.

Tegumentary Structures.

The external surface of the greater number of members of the class is thickly clothed with a peculiarly modified form of epidermis, commonly called hair. This consists of hard, elongated, slender, cylindrical or tapering, filiform, unbranched masses of epidermic material, growing from a short papilla sunk at the bottom of a follicle in the derm or true skin. Such hairs upon different parts of the same animal, or upon different animals, assume various forms, and are of various sizes and degrees of rigidity,—as seen in the delicate soft velvety fur of the Mole, the stiff bristles of the Pig, and the spines of the Hedgehog and Porcupine, all modifications of the same structures. These differences arise mainly from the different arrangement of the constituent elements into which the epithelial calls are modified. Each hair is composed usually of a cellular pithy internal portion, containing much air, and a denser or more horny cortical part. In some animals, as Deer, the substance of the hair is almost entirely composed of the medullary or cellular substance, and it is consequently very easily broken; in others the horny part prevails almost exclusively, as in the bristles of the Wild Boar. In the Three-toed Sloth (Bradypus) the hairs have a central horny axis and a pithy exterior. Though generally nearly smooth, or but slightly scaly, the surface of some hairs is strongly imbricated, notably so in some Bats, while in the Two-toed Sloth (Choloepus) they are longitudinally grooved or fluted. Though usually more or less cylindrical or circular in section, they are often elliptical or flattened, as in the curly-haired races of men, the terminal portion of the hair of Moles and Shrews, and conspicuously in the spines of the Rodents Xerus and Platacanthomys. Hair having a property of mutual cohesion or “felting,” which depends upon a roughened scaly surface and a tendency to curl, as in domestic Sheep (in which animals this property has been especially cultivated by selective breeding), is called “wool.”

In a large number of mammals hairs of one kind only are scattered pretty evenly over the surface, but in many there are two kinds, one longer, stiffer, and alone appearing on the surface, and the other shorter, finer, and softer, constituting the under fur, analogous to the down of birds. In most cases hairs of a different character from those of the general surface grow in special regions, forming ridges or tufts on the median dorsal or ventral surface or elsewhere. The tail is very often completed in this way by variously disposed elongated hairs. The margins of the eyelids are almost always furnished with a special row of stiffish hairs, called cilix or eyelashes, and in most mammals specially modified hairs, constituting the vibrissx or whiskers, endowed, through the abundant nerve supply of their basal papillae, with special tactile powers, grow from the lips and cheeks. In some mammals the hairy covering is partial and limited to particular regions; in others, as the Hippopotamus and the Sirenia, though scattered over the whole surface, it is extremely short and scanty; but in none is it reduced to so great an extent as in the Cetacea, in which it is limited to a few small bristles confined to the neighbourhood of the lips and nostrils, and often only present in the young or even foetal condition.

Some kinds of hairs, as those of the mane and tail of the Horse, appear to persist throughout the life-time of the animal; but more generally, as in the case of the body hair of. the same animal, they are shed and renewed periodically, generally annually. Many mammals have a longer hairy coat in winter, which is shed as summer comes on; and some few, which inhabit countries covered in winter with snow, as the Arctic Fox, Variable Hare, and Ermine, undergo a complete change of colour in the two seasons, being white in winter, and grey or brown in summer. The several species of Cape Mole (Chrysochloris), the Desmans or Water Moles {Myogale∖ and Potamogale velox are remarkable as being the only mammals whose hair reflects those iridescent tints so common in the feathers of tropical birds.

The principal and most obvious purpose of the hairy covering is to protect the skin against external influences, especially cold and damp. Its function in the hairless Cetacea is supplied by the specially modified and thickened layer of adipose tissue beneath the skin called “blubber.”

True scales, or flat imbricated plates of horny material, covering the greater part of the body, so frequently occurring in reptiles, are found in one family only of mammals, the Manidx or Pangolins; but these are also associated with hairs growing from the intervals between the scales or on the parts of the skin not covered by them. Similarly imbricated epidermic productions form the covering of the under surface of the tail of the flying Rodents of the genus Anomalurus ; and flat scutes, with the edges in apposition, and not overlaid, clothe both surfaces of the tail of the Beaver, Rats, and others of the same order, and also of some Insectivores and Marsupials. The Armadillos alone have an ossified exoskeleton, composed of plates of true bony tissue, developed in the derm or corium, and covered withscutes of horny epidermis. Other epidermic appendages are the horns of Ruminants and Rhinoceroses,—the former being elongated, tapering, hollow caps of hardened epidermis of fibrillated structure, fitting on and growing from conical projections of the frontal bone, and always arranged in pairs, while the latter are of similar structure, but without any internal bony support, and situated in the median line. Callosities, or bare patches covered with hardened and thickened epidermis, are found over the ischial tuberosities of many apes, the sternum of camels, on the inner side of the limbs of the Equidx, the grasping under surface of the tail of prehensile-tailed monkeys, &c. The greater part of the skin of both species of one-horned Asiatic Rhinoceros is immensely thickened and stiffened by increase of the tissue both of the derm and epiderm, constituting the well known jointed “armour-plated” hide of those animals.

With very few exceptions, the terminal extremities of the digits of both limbs are more or less protected or armed by epidermic plates or sheaths, constituting the various forms of nails, claws, or hoofs. These are wanting in the Cetacea alone. A perforated spur, with a special secreting gland in connexion with it, is found attached to the hind leg of the males of the two species of Monotremata, the Ornithorhynchus and Echidna.

Besides the universally distributed sebaceous glands connected with the pilose system, most mammals have special glands situated in modified portions of the integument, often involuted to form a shallow recess or a deep sac with a narrow opening, situated in various parts of the surface of the body, and which secrete odorous substances, by the aid of which individuals appear to recognize one another, and which probably afford the principal means by which wild animals are able to become aware of the presence of other members of the species, even at great distances. Although the commencement of the modifications of portions of the external covering for the formation of special secretions may be at present difficult to understand, the principle of natural selection will readily explain how such organs can become fixed and gradually increase in development in any species, especially as there would probably be a corresponding modification and increased sensibility of the olfactory organs. Such individuals as by the intensity and peculiarity of their scent had greater power of attracting the opposite sex would certainly be those most likely to leave descendants to inherit and in their turn propagate the modification.

To this group of structures belong the suborbital gland or “crumen” of Antelopes and Deer, the frontal gland of the Muntjak and of Bats of the genus Phyllorhina, the submental gland of the Chevrotains and of Taphozous and some other Bats, the post-auditory follicle of the Chamois, the temporal gland of the Elephant, the lateral glands of the Musk-Shrew, the lumbar gland of the Peccary, the inguinal glands of Antelopes, the preputial glands of the Musk Deer and Beaver (both so well known for the use made of their powerfully odorous secretion in medicine and perfumery) and also of the Swine and Hare, the anal glands of Carnivora, the perineal gland of the Civet (also of commercial value), the caudal glands of the Fox and Goat, the gland on the humeral membrane of Bats of the genus Saccopteryx, the post-digital gland of the Rhinoceros, the inter-digital glands of the Sheep and many Ruminants, and numerous others. In some of these cases the glands are peculiar to, or more largely developed in, the male; in others they are found equally developed in both sexes.

Dental System.

The dental system of mammals may be considered rather more in detail than space permits for some other portions of their structure, both on account of the important part it plays in the economy of the animals of this class, and of its interest to zoologists as an aid in classification and identification of species. Owing to the imperishable nature of their tissues, teeth are preserved for an indefinite time, and in the case of extinct species often offer the only indications available from which to derive an idea of the characters, affinities, and habits of the animal to which they have belonged. Hence even their smallest modifications have received great attention from comparative anatomists, and they have formed the subject of many special monographs.

Teeth are present in nearly all mammals, and are applied to various purposes. They are, however, mainly subservient to the function of alimentation, being used either in procuring food by seizing and killing living prey or gathering and biting off portions of vegetable material, and more indirectly in tearing or cutting through the hard protective coverings of food substances, as the husks and shells of nuts, or in pounding, crushing, or otherwise mechanically dividing the solid materials before swallowing, so as to prepare them for digestion in the stomach. Certain teeth are also, in many animals most efficient weapons of offence and defence, and for this purpose alone, quite irrespective of subserviency to the digestive process, are they developed in the male sex of many herbivorous animals, in the females of which they are absent or rudimentary.

Teeth belong essentially to the tegumentary or dermal system of organs, and, as is well seen in the lower vertebrates, pass by almost insensible gradations into the hardened spines and scutes formed upon the integument covering the outer surface of the body, but in mammals they are more specialized in structure and limited in locality.. In this class they are developed only in the gums or fibro-mucous membrane covering the alveolar borders of the upper and lower jaw or the premaxillary and maxillary bones and the mandible. In the process of development, for the purpose of giving them that support which is needful for the performance of their functions, they almost always become implanted in the bone,—the osseous tissue growing up and moulding itself around the lengthening root of the tooth, so that ultimately they become apparently parts of the skeleton. In no mammal, however, does ankylosis or bony union between the tooth and jaw normally take place, as in many fishes and reptiles,—a vascular layer of connective tissue, the alveolo-dental membrane, always intervening.

The presence of two or more roots, frequently met with in mammals, implanted into corresponding distinct sockets of the jaw, is peculiar to animals of this class.

The greater number of mammalian teeth when fully formed are not simple and homogeneous in structure, but are composed of several distinct tissues.

1. The pulp, a soft substance, consisting of a very delicate gelatinous connective tissue, in which numerous cells are imbedded, and abundantly supplied with blood-vessels and nerves, constitutes the central axis of all the basal part of the tooth, and affords the means by which the vitality of the whole is preserved. The nerves which pass into the pulp and endow the tooth with sensibility are branches of the fifth pair of cranial nerves. The pulp occupies a larger relative space, and performs a more important purpose in the young growing tooth than afterwards, as by the calcification and conversion of its outer layers the principal hard constituent of the tooth, the dentine, is formed. In teeth which have ceased to grow the pulp occupies a comparatively small space, which in the dried tooth is called the pulp cavity. This communicates with the external surface of the tooth by a small aperture at the apex of the root, through which the branches of blood-vessels and nerves, by which thg tooth receives its nutrition and sensitiveness, pass in to be distributed in the pulp. In growing teeth the pulp cavity is widely open below, while in advanced age it often becomes obliterated, and the pulp itself entirely converted into bone-like material.

2. The dentine or ivory forms the principal constituent of the greater number of teeth. When developed in its most characteristic form, it is a very hard but elastic substance, white, with a yellowish tinge, and slightly translucent. It consists of an organic matrix, something like but not identical with that of bone, richly impregnated with calcareous salts (chiefly phosphate of lime), these constituting in a fresh human tooth 72 per cent, of its weight. When subjected to microscopical examination it is seen to be everywhere permeated by nearly parallel branching tubes which run, in a slightly curving or wavy manner, in a general direction from the centre towards the free surface of the tooth. These tubes communicate by open mouths with the pulp cavity, and terminate usually near the periphery of the dentine, by closed ends or loops, though in Marsupials and certain other mammals they penetrate into the enamel. They are occupied in the living tooth by soft gelatinous fibrils connected with the cells of the pulp. A variety of dentine, permeated by canals containing blood-vessels, met with commonly in fishes and in some few mammals, as the Megatherium, is called vasodentine. Other modifications of this tissue occasionally met with are called osteo-dentine and secondary dentine,— the latter being a dentine of irregular structure which often fills up the pulp cavity of old animals.

3. The enamel constitutes a thin investing layer, complete or partial, of the outer or exposed and working surface of the dentine of the crown of the teeth of most mammals. This is the hardest tissue met with in the animal body, containing from 95 to 97 per cent, of mineral substances (chiefly phosphate and some carbonate of lime, with traces of fluoride of calcium). Its ultimate structure consists of prismatic fibres, placed generally with their long axes at right angles to the free surface of the tooth. Enamel is easily distinguished from dentine with the naked eye, by its clear, bluish-white, translucent appearance.

4. The cementum or crusta petrosa is always the most externally placed of the hard tissues of which teeth are composed, as will be understood when the mode of development of these organs is considered. It is often only found as a thin layer upon the surface of the root, but sometimes, as in the complex-crowned molar teeth of the Horse and Elephant, it is a structure which plays a very important part, covering and filling in the interstices between the folds of the enamel. In appearance, histological structure, and chemical composition it is closely allied to osseous tissue, containing lacunae and canaliculi, though only when it is of considerable thickness are Haversian canals present in it.

Development of the Teeth.— The two principal constituents of the teeth, the dentine and the enamel, are developed from the two layers of the buccal mucous membrane, the dentine from the submucous, the enamel from the epithelial layer. The latter dips down into the substance of the gum, and forms the enamel organ or germ, the first rudiment of the future tooth, which is constantly present even in those animals in which the enamel is not found as a constituent of the perfectly-formed tooth. Below the mass of epithelial cells thus embedded in the substance of the gum, and remaining connected by a narrow neck of similar structure with the epithelium of the surface, a portion of the vascular submucous areolar tissue becomes gradually separated and defined from that which surrounds it, and assumes a distinct form, which is that of the crown of the future tooth,—a single cone in the case of simple teeth, or with two or more eminences in the complex forms. This is called the dental papilla or dentine germ, and by the gradual conversion of its tissue into dentine the bulk of the future tooth is formed, the uncalcified central portion remaining as the pulp. The conversion of the papilla into hard tissue commences at the outer surface of the apex, and gradually proceeds downwards and inwards, so that the form of the papilla exactly determines the form of the future dentine, and no alteration either in shape or size of this portion of the tooth, when once calcified, can take place by addition to its outer surface. In the meanwhile calcification of portion of the cells of the enamel organ, which adapts itself like a cap round the top of the dentinal papilla, and has assumed a somewhat complex structure, results in the formation of the enamel coating of the crown of the tooth. While these changes are taking place the tissues immediately surrounding the tooth germ become condensed and differentiated into a capsule, which appears to grow up from the base of the dental papilla, and encloses both this and the enamel germ, constituting the follicle or tooth sac. By the ossification of the inner layer of this follicle, the cementum is formed. This substance therefore, unlike the dentine, increases from within outwards, and its growth may therefore be the cause of considerable modification of form and enlargement, especially of the roots, of certain teeth, as those of Seals and some Cetacea. The delicate homogeneous layer which coats the enamel surface of newly-formed teeth, in which cementum is not found in the adult state, and known as Nasmyth’s membrane, is considered by Tomes as probably a film of this substance, too thin to exhibit its characteristic structure, though by others it is believed to be derived from the external layer of the enamel organ. The homology of the teeth with the dermal appendages, hairs, scales, and claws has already been alluded to, and it will now be seen that in both cases two of the primary embryonic layers are concerned in their development, the mesoblast and epiblast, although in very different proportions. In the hair or nail the part derived from the epiblast forms the principal bulk of the organ, the mesoblast only constituting the papilla or matrix. In the tooth the epiblastic portion is limited to the enamel, always of relatively small bulk and often absent, while the dentine (the principal constituent of the tooth) and the cementum are formed from the mesoblast.

When more than one set of teeth occur in mammals, those of the second set are developed in a precisely similar manner to the first, but the enamel germ, instead of being derived directly from an independent part of the oral epithelium, is formed from a budding out of the neck of the germ of the tooth succeeded. In the case of the true molars which have no predecessors, the germ of the first has an independent origin, but that of the others is derived from the neck of the germ of the tooth preceding it in the series. The foundations of the permanent teeth are thus laid as it were almost simultaneously with those of their predecessors, although they remain in many cases for years before they are developed into functional activity.

Although the commencement of the formation of teeth takes place at an early period of embryonic life, they are in nearly all mammals still concealed beneath the gum at the time of birth. The period of eruption, or “cutting” of the teeth as it is called, that is, their piercing through and rising above the surface of the mucous membrane, varies much in different species. In some, as Seals, the whole series of teeth appear almost simultaneously; but more often there are considerable intervals between their appearance, the front teeth usually coming into place first, and those at the back of the mouth at a later period. General Characters.— The simplest form of tooth may be exemplified on a large scale by the tusk of the Elephant ' (fig. 1, I.). It is a hard mass almost entirely composed of dentine, of a conical shape at first, but during growth becoming more and more cylindrical or uniform in width. The enamel covering, present on the apex in its earliest condition, soon disappears, but a thin layer of cementum covers the circumference of the tooth throughout life. On section it will be seen that the basal portion is hollow, and contains a large conical pulp, as broad at the base as the tooth itself, and deeply imbedded in the bottom of a recess or socket in the upper maxillary bone. This pulp continues to grow during the lifetime of the animal, and to be converted at its surface into dentine. The tooth therefore continually elongates, but the use to which the animal subjects it in its natural state causes the apex to wear away, at a rate generally proportionate to the growth at the base, otherwise it would become of inconvenient length and weight. Such teeth of indefinite growth are said to be “rootless,” or to have “persistent pulps.”

One of the corresponding front teeth of man (fig. 1, II. and III.) may be taken as an example of a very different condition. After its crown is fully formed by calcification of the germ, the pulp, though continuing to elongate, begins to contract in diameter; a neck or slight constriction is formed; and the remainder of the pulp is converted into the root (or fang), a tapering conical process which is imbedded in the alveolar cavity of the bone, and has at its extremity a minute perforation, through which the vessels and nerves required to maintain the vitality of the tooth enter the pulp cavity, very different from the widely open cavity at the base of the growing tooth. When the crown of the tooth is broad and complex in character, instead of having a single root, it may be supported by two or more roots, each of which is implanted in a distinct alveolar recess or socket, and to the apex of which a branch of the common pulp cavity is continued (fig. 1, IV.). Such teeth are called “rooted teeth.” When they have once attained their position in the jaw, with the neck a little way above the level of the upper margin of the alveolus, and embraced by the gum or tough fibro-vascular membrane which covers the alveolar border, and having the root fully formed, they can never increase in length or alter their position. If they appear to do so in old age it is only in consequence of absorption and retrocession of the surrounding alveolar margins. If, as often happens, their surface wears away in mastication, it is never renewed. The open cavity at the base of the imperfectly developed rooted tooth (fig. 1, II.) causes it to resemble the persistent condition of the rootless tooth. The latter is therefore a more primitive condition, the formation of the root being a completion of the process of tooth development. Functionally it is, however, difficult to say that the one is a higher form than the other, as they both serve important and different purposes in the animal economy.

As is almost always the case in nature, intermediate conditions between these two forms of teeth are met with. Some, as the molars of the Horse, and of many Rodents, are for a time rootless, and have growing pulps producing a very long crown with parallel sides, the summit of which may be in use and beginning to wear away while the base is still growing, but ultimately the pulp contracts, forms a neck and distinct roots, and ceases to grow. The canine tusks of the Musk Deer and of the Walrus have persistent pulps, and are open at their base until the animal is of advanced age, when they close, and the pulp ceases to be renewed.

The simplest form of the crown of a tooth is that of a cone; but this may be variously modified. It may be flattened, with its edges sharp and cutting, and pointed at the apex, as in the laterally compressed premolars of most Carnivora, or it may be chisel-or awl-shaped, with a straight truncated edge, as in the human incisors; or it may be broad, with a flat or rounded upper surface. Very often there is a more or less prominent ridge encircling the whole or part of the base of the crown just above the neck, called the cingulum, which serves as a protection to the edge of the gum in masticating, and is best developed in flesheating and insectivorous animals, in which the gums are liable to be injured by splinters of bone or other hard fragments of their food. The form of the crown is frequently rendered complex by the development upon its surface of elevations or tubercles called cusps, or by ridges usually transverse, but sometimes variously curved or folded. When the crown is broad and the ridges greatly developed, as in the molars of the Elephant, Horse, and Ox (fig. 1, V.), the interspaces between them are filled with cementum, which supports them and makes a solid compact mass of the whole tooth. When such a tooth wears away at the surface by friction against the opposed tooth of the other jaw, the different density of the layers of the substances of which it is composed—enamel, dentine, and cementum— arranged in characteristic patterns, causes them to wear unequally, the hard enamel ridges projecting beyond the others, thus giving rise to a grinding surface of great mechanical advantage.

Succession of Teeth.— The dentition of all mammals consists of a definite set of teeth almost always of constant and determinate number, form, and situation, and, with few exceptions, persisting in a functional condition throughout the natural term of the animal’s life. In many species these are the only teeth which the animal ever possesses. —the set which is first formed being permanent, or, if accidentally lost, or decaying in extreme old age, not being replaced by others. These animals are called Monophyodont. But, in the larger number of mammals, certain of the teeth are preceded by others, which may be only of a very transient, rudimentary, and functionless character (being in the Seals, for example, shed either before or within u few days after birth), or may be considerably developed, and functionally occupy the place of the permanent teeth for a somewhat lengthened period, during the growth and development of the latter and of the jaws. In all cases these teeth disappear (by the absorption of their roots and shedding of the crowns) before the frame of the animal has acquired complete maturity as evidenced by the coalescence of the epiphyses of the osseous system. As these teeth are, as a general rule, present during the period in which the animal is nourished by the milk of the mother, the name of “milk teeth” (French dents de lait, German Milchzähne) has been commonly accorded to them, although it must be understood that the epoch of their presence is by no means necessarily synchronous with that of lactation·. Animals which possess such teeth are called Diphyodont. No mammal is known to have more than two sets of teeth; and the definite and orderly replacement of certain members of the series is a process of quite a different nature from the indefinite succession which takes place in all the teeth continuously throughout the lifetime of the lower vertebrates.

When the milk teeth are well developed, and continue in place during the greater part of the animal’s growth, as is especially the case with the Ungulata, and, though to a less degree, with the Primates and Carnivora, their use is obvious, as taken all together they form structurally a complete epitome on a small scale of the more numerous and larger permanent set (see fig. 3), and, consequently, are able to perform the same functions, while time is allowed for the gradual maturation of the latter, and especially while the jaws of the growing animal are acquiring the size and strength sufficient to support the permanent teeth. Those animals, therefore, that have a well-developed and tolerably persistent set of milk teeth may be considered to be in a higher state of development, quoad dentition, than those that have the milk teeth absent or rudimentary.

It is a very general rule that individual teeth of the milk and permanent set have a close relationship to one another, being originally formed, as mentioned above, in exceedingly near proximity, and with, at all events as far as the enamel germ is concerned, a direct connexion. Moreover, as the latter ultimately come to occupy the position in the alveolar border temporarily held by the former, they are spoken of respectively as the predecessors or successors of each other. But it must be understood that milk teeth may be present which have no successors in the permanent series, and, what is far more general, permanent teeth may have no predecessors in the milk series.

The complete series of permanent teeth of most mammals forms a complex machine, with its several parts adapted for different functions,—the most obvious structural modification for this purpose being an increased complexity of the individual components of the series from the anterior towards the posterior extremity of such series. Since, as has just been said, the complete series of the milk teeth often presents structurally and functionally a similar machine, but composed of fewer individual members, and the anterior of which are as simple, and the posterior as complex, as those occupying corresponding positions in the permanent series,—and since the milk teeth are only developed in relation to the anterior or lateral, never to the most posterior of the permanent series,—it follows that the hinder milk teeth are usually more complex than the teeth of which they are the predecessors in the permanent series, and represent functionally, not their immediate successors, but those more posterior permanent teeth which have no direct predecessors. This character is clearly seen in those animals in which the various members of the molar series are well differentiated from each other in form, as the Carnivora, and also in Man.

In animals which have two sets of teeth the number of the teeth of the permanent series which are preceded by milk teeth varies greatly, being sometimes, as in Marsupials and some Rodents, as few as one on each side of each jaw, and sometimes including the larger portion of the series.

Although there are difficulties in some cases in arriving at a satisfactory solution of the question, it is, on the whole, safest to assume that when only one set of teeth is present, these correspond to the permanent teeth of the Diphyodonts. When this one set is completely developed, and remains in use throughout the animal’s life, there can be no question on this subject. When, on the other hand, the teeth are rudimentary and transient, as in the Whalebone Whales, it is possible to consider them as representing the milk series; but there are weighty reasons in favour of the opposite conclusion. General Arrangement, Homologies, and Notation of Teeth of Mammals.— The teeth of the two sides of the jaws are always alike in number and character, except in cases of accidental or abnormal variation, and in the one remarkable instance of constant deviation from bilateral symmetry among mammals, the tusks of the Narwhal (see fig. 49, p. 398), in which the left is of immense size, and the right rudimentary. In those animals also, as the Dolphins and some Armadillos, which have a very large series of similar teeth, not always constant in number in different individuals, there may be differences in the two sides; but, apart from these, in describing the dentition of any mammal, it is quite sufficient to give the number and characters of the teeth of one side only. As the teeth of the upper and the lower jaws work against each other in masticating, there is a general correspondence or harmony between them, the projections of one series, when the mouth is closed, fitting into corresponding depressions of the other. There is also a general resemblance in the number, characters, and mode of succession of both series, so that, although individual teeth of the upper and lower jaws may not be in any strict sense of the term homologous parts, there is a great convenience in applying the same descriptive terms to the one which are used for the other.

The simplest dentition as a whole is that of many species of Dolphin (fig. 2), in which the crowns are single-pointed, slightly curved cones, and the roots also single and tapering, and all alike in form from the anterior to the posterior end of the series, though it may be with some slight difference in size, those at the two extremities of the series being rather smaller than the others. Such a dentition is called Homodont, and in the case cited, as the teeth are never changed, it is also Monophyodont. Such teeth are adapted only for catching slippery living prey, as fish.

In a very large number of mammals the teeth of different parts of the series are more or less differentiated in character, and have different functions to perform. The front teeth are simple and one-rooted, and are adapted for cutting and seizing. They are called “incisors.” The back teeth have broader and more complex crowns, tuberculated or ridged, and they are supported on two or more roots. They crush or grind the food, and are hence called “molars.” Many animals have, between these two sets, a tooth at each corner of the mouth, longer and more pointed than the others, adapted for tearing or stabbing, or for fixing struggling prey. From the conspicuous development of such teeth in the Carnivora, especially the Dogs, they have received the name of “canines.” A dentition with its component parts so differently formed that these distinctive terms are applicable to them is called Heterodont. In most cases, though by no means invariably, animals with Heterodont dentition are also Diphyodont.

This general arrangement is extremely obvious in a considerable number of mammals; and closer examination shows that, under very great modifications in detail, there is a remarkable uniformity of essential characters in the dentition of a large number of members of the class belonging to different orders and not otherwise closely allied, so much that it has been possible (chiefly through the researches of Professor Owen) to formulate a common plan of dentition from which the others have been derived by the alteration of some and suppression of other members of the series, and occasionally, but very rarely, by addition. The records of palaeontology fully confirm this view, as by tracing back many groups now widely separated in dental characters we find a gradual approximation to a common type. In this generalized form of mammalian dentition (which is best exemplified in the genera Λnoplotherium and Homalodontotherium) the entire number of teeth present is 44, or 11 above and 11 below on each side. Those of each jaw are placed in continuous series without intervals between them; and, although the anterior teeth are simple and single-rooted, and the posterior teeth complex and with several roots, the transition between the two kinds is gradual.

In dividing and grouping such teeth for the purpose of description and comparison, more definite characters are required than those derived merely from form or function. The first step towards a classification has been made by the observation that the upper jaw is composed of two bones, the premaxilla and the maxilla, and that the suture between these bones separates the three anterior teeth from the others. These three teeth then, which are implanted by their roots in the premaxilla, form a distinct group, to which the name of “incisor” is applied. This distinction is, however, not so important as it appears at first sight, for, as mentioned when speaking of the development of the teeth, their connexion with the bone is only of a secondary nature, and, although it happens conveniently for our purpose that in the great majority of cases the segmentation of the bone coincides with the interspace between the third and fourth tooth of the series, still, when it does not happen to do so, as in the case of the Mole, we must not give too much weight to this fact, if it contravenes other reasons for determining the homologies of the teeth. The eight remaining teeth of the upper jaw offer a natural division, inasmuch as the posterior three never have milk predecessors, and, although some of the anterior teeth may be in the same case, the particular one preceding these three always has such a predecessor. These three then are grouped apart as the “molars,” or “true molars,” as some of the teeth in front of them often have a molariform character. Of the five teeth between the incisors and molars the most anterior, or that which is usually situated close behind the premaxillary suture, almost always, as soon as any departure takes place from the simplest and most homogeneous type, assumes a lengthened and pointed form, and is the tooth so developed as to constitute the “canine” or “laniary” tooth of the Carnivora, the tusk of the Boar, &c. It is customary therefore to call this tooth, whatever its size or form, the “canine.” The remaining four are the “premolars” or “false molars.” This system of nomenclature has been objected to as being artificial, and in many cases not descriptive, the distinction between premolars and canine especially being sometimes not obvious, but the terms are now in such general use, and are so practically convenient—especially if, as it is best to do in all such cases, we forget their original signification, and treat them as arbitrary signs—that it is not likely they will be superseded by any that have been proposed as substitutes for them.

With regard to the lower teeth the difficulties are greater, owing to the absence of any suture corresponding to that which defines the incisors above; but, as the number of the teeth is the same, as the corresponding teeth are preceded by milk teeth, and as in the large majority of cases it is the fourth tooth of the series which is modified in the same way as the canine (or fourth tooth) of the upper jaw, it is quite reasonable to adopt the same divisions as with the upper series, and to call the first three, which are implanted in the part of the mandible opposite to the premaxilla, the incisors, the next the canine, the next four the premolars, and the last three the molars. It may be observed that when the mouth is closed, especially when the opposed surfaces of the teeth present an irregular outline, the corresponding upper and lower teeth are not exactly opposite, otherwise the two series could not fit into one another, but as a rule the points of the lower teeth shut into the interspaces in front of the corresponding teeth of the upper jaw. This is seen very distinctly in the canine teeth of the Carnivora, and is a useful guide in determining the homologies of the teeth of the two jaws. Objections have certainly been made to this view, because, in certain rare cases, the tooth which, according to it, would be called the lower canine has the form and function of an incisor (as in Ruminants and Lemurs), and on the other hand (as in Oreodon, an extinct Ungulate from North America) the tooth that would thus be determined as the first premolar has the form of a canine; but it should not be forgotten that, as in all such cases, definitions derived from form and function alone are quite as open to objection as those derived from position and relation to surrounding parts, or still more so.

For the sake of brevity the complete dentition, arranged according to these principles, is often described by the following formula, the numbers above the line representing the teeth of the upper, those below the line those of the lower jaw: — incisors ∣∈∣, canines ∣∈∣, premolars *~*, molars ∣∈∣ = ⅛≡Γι > tota l 44. ∙^- s > however, initial letters may be substituted for the names of each group, and it is quite unnecessary to give more than the numbers of the teeth on one side of the mouth, the formula may be conveniently abbreviated into—

*⅜> c T» P τ> m I = ⅛ι > t°t a l 44.

The individual teeth of each group are always enumerated from before backwards, and by such a formula as the following—

i 1, i 2, i 3, c, p 1, p 2, p 3, p 4, m 1, m 2, m 3 i 1, i 2, i 3, c, p 1, p 2, p 3, p 4, ml, m2, m3 a special numerical designation is given by which each one can be indicated. In mentioning any single tooth, such a sign as — will mean the first upper molar, m ’ 1 the first lower molar, and so on. The use of such signs saves much time and space in description.

It was part of the view of the founder of this system of dental notation that, at least throughout the group of mammals whose dentition is derived from this general type, each tooth has its strict homologue in all species, and that in those cases in which fewer than the typical fιumber are present (as in all existing mammals except the genera Sus, Gymnura, Talpa, and Myogale) the teeth that are missing can be accurately defined. According to this view, when the number of incisors falls short of three it is assumed that the absent ones are missing from the outer and posterior end of the series. Thus when there is but one incisor present, it is i 1; when two, they are i 1 and i 2. Furthermore, when the premolars and the molars are below their typical number, the absent teeth are missing from the fore part of the premolar series, and from the back part of the molar series. If this were invariably so, the labours of those who describe teeth would be greatly simplified; but there are unfortunately so many exceptions that a close scrutiny into the situation, relations, and development of a tooth may be required before its nature can be determined, and in some cases the evidence at our disposal is scarcely sufficient for the purpose.

The milk dentition is expressed by a similar formula, d for deciduous being commonly added before the letter expressive of the nature of the tooth. As the three molars and (almost invariably) the first premolar of the permanent series have no predecessors, the typical milk dentition would be expressed as follows— di ⅜, de ⅜, dm f = {∙ = 28. The teeth which precede the premolars of the permanent series are all called molars in the milk dentition, although, as a general rule, in form and function they represent in a condensed form the whole premolar and molar series of the adult. When there is a marked difference between the premolars and molars of the permanent dentition, the first milk molar resembles a premolar, and the last has the characters of the posterior true molar.

The dentition of all the animals of the orders Primates, Carnivora, Insectivora, Chiroptera, and Ungulata can clearly be derived from the above-described generalized type. The same may be said of the Rodents, and even the Proboscidea, though with greater modification, at least in the existing members of the order. It is also apparent in certain extinct Cetaceans, as Zeuglodon and Squalodon, but it is difficult to find any traces of it in existing Cetacea, Sirenia, or any of the so-called Edentata. All the Marsupials, different as they are in their general structure and mode of life, and variously modified as is their dentition, present in this system of organs some deep-lying common characters which show their unity of origin. The genêralized type to which their dentition can be reduced presents considerable resemblance to that of the placental mammals, yet differing in details. It is markedly heterodont, and susceptible of division into incisors, canines, premolars, and molars upon the same principles. The whole number is, however, not limited to forty-four. The incisors may be as numerous as five on each side, and are almost always different in number in the upper and the lower jaw. The premolars and molars are commonly seven, as in the placental mammals, but their arrangement is reversed, as there are four true molars and three premolars; and finally the milk dentition of all known Marsupials, existing or extinct, is (if not entirely absent) limited to a single tooth on each side of each jaw, this being the predecessor of the last permanent premolar.

In very few mammals are teeth entirely absent. Even in the Whalebone Whales their germs are formed in the same manner and at the same period of life as in other mammals, and even become partially calcified, but they never rise above the gums, and completely disappear before the birth of the animal. In soine species of the order Edentata, the true Anteaters and the Pangolins, no traces of teeth have been found at any age. The Monotremata are in like case, although the Ornithorhynchus has flattened, ridged, horny plates at the back of both jaws, which answer the purpose of molar teeth.

Modifications of the Teeth in Relation to their Functions. —The principal functional modifications noticed in the dentition of Mammalia may be roughly grouped as (1) piscivorous, (2) carnivorous, (3) insectivorous, (4) omnivorous, and (5) herbivorous, each having, of course, numerous variations and transitional conditions.

1. The essential characters of a piscivorous dentition are best exemplified in the Dolphins, and also (as modifications of the carnivorous type) in the Seals. It consists of an elongated, rather narrow mouth, wide gape, with numerous subequal, conical, sharp-pointed, recurved teeth adapted simply to rapidly seize, but not to divide or masticate, active, slippery, but not powerful prey. All animals which feed on fish as a rule swallow and digest them entire, a process which the structure of prey of this nature, especially the intimate interblending of delicate, sharp-pointed bones with the muscles, renders very advantageous, and for which the above-described type of dentition is best adapted.

2. The carnivorous type of dentition is shown in its most perfect development among existing mammals in the. Felidae. The function being here to seize and kill struggling animals, often of large size and great muscular power, the canines are immensely developed, trenchant, and piercing, and are situated wide apart so as to give the firmest hold when fixed in the victim’s body. The jaws are as short as is consistent with the free action of the canines, so that no power may be lost. The incisors are very small, so as not to interfere with the penetrating action of the canines, and the crowns of the molar series are reduced to scissor-like blades, with which to pare off the soft tissues from, the large bones, or to divide into small pieces the less dense portions of the bone for the sake of nutriment afforded by the blood and marrow it contains. The gradual modification between this and the two following types will be noticed in their appropriate places.

3. In the most typical insectivorous animals, as the Hedgehogs and Shrews, the central incisors are elongated, pointed, and project forwards, those of the upper and lower jaw meeting like the blades of a pair of forceps, so as readily to secure small active prey, quick to elude capture, but powerless to resist when once seized. The crowns of the molars are covered with numerous sharp edges and points, which working against each other, rapidly cut up the hard cased insects into little pieces, fit for swallowing and digestion.

4. The omnivorpus type, especially that adapted for the consumption of soft vegetable substances, such as fruits of various kinds, may be exemplified in the dentition of Man, of most Monkeys, and of the less modified Pigs. The incisors are moderate, subequal, and cutting. If the canines are enlarged, it is usually for other purposes than those connected with food, and only in the male sex. The molars have their crowns broad, flattened, and elevated into rounded tubercles.

5. In the most typically herbivorous forms of dentition, as seen in the Horse and Kangaroo, the incisors are well developed and trenchant, adapted for cutting off the herbage on which the animals feed; the canines are rudimentary or suppressed; the molars are large, with broad crowns, which in the simplest forms have strong transverse ridges, but may become variously complicated in the higher degrees of modification which this type of tooth assumes.

The natural groups of mammals, or those which in our present state of knowledge we have reason to believe are truly related to each other, may each contain examples of more than one of these modifications. Thus the Primates have both omnivorous and insectivorous forms. The Carnivora show piscivorous, carnivorous, insectivorous, and omnivorous modifications of their common type of dentition. The Ungulata and the Rodentia have among them the omnivorous and various modifications, both simple and complex, of the herbivorous type. The Marsupialia exhibit examples of all forms, except the purely piscivorous. Other orders, more restricted in number or in habits, as the Proboscidea and Cetacea, naturally do not show so great a variety in the dental structure of their members.

In considering the taxonomic value to be assigned to the modifications of teeth of mammals, two principles, often opposed to each other, which have been at work in producing these modifications, must be held in view :—(1) the type, or ancestral form, as we generally now call it, characteristic of each group, which in most mammals is itself derived from the still more generalized type described above; and (2) variations which have taken place from this type, generally in accordance with special functions which the teeth are called upon to fulfil in particular cases. These variations are sometimes so great as completely to mask the primitive type, and in this way the dentition of many animals of widely different origin has come to present a remarkable superficial resemblance, as in the case of the Wombat (a Marsupial), the Aye-Aye (a Lemur), and the Rodents, or as in the case of the Thylacine and the Dog. In all these examples indications may generally be found of the true nature of the case by examining the earlier conditions of dentition; for the characters of the milk teeth or the presence of rudimentary or deciduous members of the permanent set will generally indicate the route by which the specialized dentition of the adult has been derived. It is perhaps owing to the importance of the dental armature to the well-being of the animal in procuring its sustenance, and preserving its life from the attacks of enemies, that great changes appear to have taken place so readily, and with such comparative rapidity, in the form of these organs, changes often accompanied with but little modification in the general structure of the animal. Of this proposition the Aye-Aye (Chiromys) among Lemurs, the Walrus among Seals, and the Narwhal among Dolphins form striking examples; as, in all, the superficial characters of their dentition would entirely separate them from the animals with which all other evidence (even including the mode of development of their teeth) proves their close affinity.

The Skeleton.

The skeleton is a system of hard parts, forming a framework which supports and protects the softer organs and tissues of the body. It consists of dense fibrous and cartilaginous tissues, of which portions remain through life in this state, but the greater part is transformed during the growth of the animal into bone or osseous tissue. This is characterized by a peculiar histological structure and chemical composition, being formed mainly of a gelatinous basis, strongly impregnated with salts of lime, chiefly phosphate, and disposed in a definite manner, containing numerous minute nucleated spaces or cavities called lacunae, connected together by delicate channels or canaliculi, which radiate in all directions from the sides of the lacunae. Parts composed of bone are, next to the teeth, the most imperishable of all the organs of the body, often retaining their exact form and internal structure for ages after every trace of all other portions of the organization has completely disappeared, and thus, in the case of extinct animals, affording the only means of attaining a knowledge of their characters and affinities.

In the Armadillos and their extinct allies alone is an ossified exoskeleton, or bony covering developed in the skin, present. In all other mammals the skeleton is completely internal. It may be described as consisting of an axial portion belonging to the head and trunk, and an appendicular portion belonging to the limbs. There are also certain bones called splanchnic, being developed within the substance of some of the viscera. Such are the os cordis and os penis found in some mammals.

It is characteristic of all the larger bones of the Mammalia, that their ossification takes its origin from several distinct centres. One near the middle of the bone, and spreading throughout its greater portion, constitutes the diaphysis, or “shaft,” in the case of the long bones. Others near the extremities, or in projecting parts, form the epiphyses, which remain distinct during growth, but ultimately coalesce with the rest of the bone.

The axial skeleton consists of the skull, the vertebral column (prolonged at the posterior extremity into the tail), the sternum, and the ribs.

In the skull of adult mammals, all the bones, except the lower jaw, the auditory ossicles, and the bones of the hyoid arch, are immovably articulated together, their edges being in close contact, often interlocking by means of fine denticulations projecting from one bone and fitting into corresponding depressions of the other, and held together by the periosteum, or fibrous membrane investing the bones, passing directly from one to the other, permitting no motion, beyond perhaps a slight yielding to external pressure. In old animals there is a great tendency for the different bones to become actually united by the extension of ossification from one to the other, with consequent obliteration of the sutures. The cranium, thus formed of numerous originally independent ossifications, retaining through life more or less of their individuality, or all fused together, according to the species, the age, or even individual peculiarity, consists of a brain case, or bony capsule for enclosing and protecting the brain, and a face for the support of the organs of sight, smell, and taste and of those concerned in seizing and masticating the food. The brain case articulates directly with the anterior cervical vertebra, by means of a pair of oval eminences, called condyles, placed on each side of the large median foramen which transmits the spinal cord. It consists of a basal axis, continuous serially with the axes or centra of the vertebrae, and of an arch above, roofing over and enclosing the cavity which contains the cephalic portion of the central nervous system (see fig. 4). The base with its arch is composed of three segments placed one before the other, each of which is comparable to a vertebra with a greatly expanded neural arch. The hinder or occipital segment consists of the basi-occipitâl, ex-occipital, and supra-occipital bones; the middle segment of the basi-sphenoid, ali-sphenoid, and parietal bones; and the anterior segment of the presphenoid, orbito-sphenoid, and frontal bones. The axis is continued forwards into the mesethmoid, or septum of the nose, around which the bones of the face are arranged in a manner so extremely modified for their special purposes that anatomists who have attempted to trace their serial homologies with the more simple portions of the axial skeleton have arrived at very diverse interpretations. The characteristic form and structure of the face of mammals is mainly dependent upon the size and shape of (1) the orbits, a pair of cup-shaped cavities for containing the eyeball and its muscles, which may be directed forwards or laterally, placed near together or wide apart, and may be completely or only partially encircled by bone; (2) the nasal fossae, cavities on each side of the median nasal septum, and forming the passage for the air to pass between the external and the internal nares, and containing in their upper part the organ of smell; (3) the zygomatic arch,, a bridge of bone for the purpose of muscular attachment, which extends from the side of the face to the skull, overarching the temporal fossa; (4) the roof of the mouth, with its alveolar margin for the implantation of the upper teeth. The face is completed by the mandible, or lower jaw, consisting of two lateral rami, articulated by a hinge joint with the squamosal (a cranial bone interposed between the posterior and penultimate segment of the brain case, where also the bony capsule of the organ of hearing is placed), each being composed of a single solid piece of bone, and united together in the middle line in front, at the symphysis,—which union may be permanently ligamentous or become completely ossified. Into the upper border of the mandibular rami the lower teeth are implanted.

In only those species in which the brain holds a large relative proportion to the rest of the body, as in Man and the smaller species of the Primates and some other orders, does the external form of the skull receive much impress from the real shape of the cavity containing the brain. The size and form of the mouth, and the modifications of the jaws for the support of teeth of various shape and number, the ridges and crests on the cranium for the attachment of the muscles necessary to put this apparatus in motion, outgrowths of bone for the enlargement of the external surface required for the support of sense organs or of weapons, such as horns or antlers (which outgrowths, to prevent undue increase of weight, are filled with cells containing air), cause the principal variations in the general configuration of the skull. These variations are, however, only characteristically developed in perfectly adult animals, and are in many cases more strongly marked in the male than the female sex. Throughout all the later stages of growth up to maturity the size and form of the brain case remain comparatively stationary, while the accessory parts of the skull rapidly increase and take on their distinctive development characteristic of the species.

The hyoidean apparatus in mammals supports the tongue and larynx, and consists of a median portion below, the basi-hyal, from which two pairs of half arches, or cornua, extend upwards and outwards. The anterior is the most important, being connected with the periotic bone of the cranium. It may be almost entirely ligamentous, but more often has several ossifications, the largest of which is usually the stylo-hyal. The posterior cornu (thyro-hyal) is united at its extremity with the thyroid cartilage of the larynx, which it suspends in position. The median portion, or basi-hyal, is sometimes, as in the Howling Monkeys, enormously enlarged and hollowed, admitting into its cavity an air-sac connected with the organ of voice.

The vertebral column consists of a series of distinct bones called vertebrae, arranged in close connexion with each other along the dorsal side of the neck and trunk, and in the median line. It is generally prolonged posteriorly beyond the trunk, to form the axial support of the appendage called the tail. Anteriorly it is articulated with the occipital region of the skull. The number of distinct bones of which the vertebral column is composed varies greatly among the Mammalia, the main variation being due to the elongation or otherwise of the tail. Apart from this, in most mammals the number is not far from thirty, though it may fall as low as twenty-six (as in some Bats), or rise as high as forty {IIyrax and Choloepus'). The different vertebrae, with some exceptions, remain through life quite distinct from each other, though closely connected by means of fibrous structures which allow of a certain, but limited, amount of motion between them. The exceptions are the following :—near the posterior part of the trunk, in nearly all mammals which possess completely developed hinder limbs, two or more vertebrae become ankylosed together to form the “sacrum,” the portion of the vertebral column to which the pelvic girdle is attached; also, in certain species of Whales and of Armadillos, there are constant ossifie unions of certain vertebrae of the cervical region.

Although the vertebrae of different regions of the column of the same animal or of different animals present great diversities of form, there is a certain general resemblance among them, or a common plan on which they are constructed, which is more or less modified by alteration of form or proportions, or by the addition or suppression of parts to fit them to fulfil their special purpose in the economy. An ordinary or typical vertebra consists in the first place of a solid piece of bone, the body or centrum (fig. 5, c), of the form of a disk or short cylinder. The bodies of contiguous vertebrae are connected together by a very dense, tough, and elastic material called the “intervertebral substance,” of peculiar and complex arrangement. This substance forms the main, and in some cases the only,, union between the vertebrae. Its elasticity provides for the vertebrae always returning to their normal relation to each other and to the column generally, when they have been disturbed therefrom by muscular action. A process (p) arises on each side from the dorsal surface of the body. These, meeting in the middle line above, form together an arch, surmounting a space or short canal (nc). As in this space lies the posterior prolongation of the great cerebrospinal nervous axis, or spinal cord, it is called the neural canal, and the arch is called the neural arch, in contradistinction to another arch on the ventral surface of the body of the vertebra, called tlιe haemal arch. The last is, however, never formed in mammals by any part of the vertebra itself, but only by certain distinct bones placed more or less in apposition to it—the ribs in the thoracic, and the “chevron bones” in the caudal region. In most cases the arch of one vertebra is articulated with that of the next by distinct surfaces with synovial joints, placed one on each side, called “zygapophyses” (2), but these are often entirely wanting when flexibility is more needed than strength, as in the greater part of the caudal region of long-tailed animals. In addition to the body and the arch, there are certain projecting parts called processes, chiefly serving for the attachment of the numerous muscles which move the vertebral column. Of these two are single and median,—the spinous process or neural spine, or neurapophysis (⅛∙), arising from the middle of the upper part of the arch, and the hypapophysis from the under surface of the body. This, however, is as frequently absent as the former is constant. The other processes are paired and lateral. They are transverse processes (t), of which there may be two, an upper and a lower, in which case the former is called, in the language of Owen (to whom we are indebted for the terminology of the parts of vertebrae in common use), “diapophysis,” and the latter “parapophysis.” Other processes less constantly present are called respectively “metapophyses” (τn) and “anapophyses” (a).

The vertebral column is divided for convenience of description into five regions, the cervical, thoracic or dorsal, lumbar, sacral, and caudal. This division is useful, especially as it is not entirely arbitrary, and in most cases is capable of ready definition; but at the contiguous extremities of the regions the characters of the vertebrae of one are apt to blend into those of the next region, either normally or as peculiarities of individual skeletons.

The cervical region constitutes the most anterior portion of the column, or that which joins the cranium. The vertebrae which belong to it are either entirely destitute of movable ribs, or if they have any these are small, and do not join the sternum. As a general rule they have a considerable perforation through the base of the transverse process (the vertebrarterial canal (fig. 7, t), or, as it is sometimes described, they have two transverse processes, superior and inferior, which, meeting at their extremities, enclose a canal. This, however, rarely applies to the last vertebra of the region, in which only the upper transverse process is usually developed. The transverse process, moreover, very often sends down near its extremity a more or less compressed plate (inferior lamella), which, being considered to be serially homologous with the ribs of the thoracic vertebrae (though not developed autogenously), is often called the “costal” or “pleurapophysial” plate. This is usually largest on the sixth, and altogether wanting on the seventh vertebra. The first and second cervical vertebrae, called respectively “atlas” and “axis,” are specially modified for the function of supporting and permitting the free movements of the head. They are not united together by the intervertebral substance, but connected only by ordinary ligaments and synovial joints.

The cervical region in mammals presents the remarkable peculiarity that, whatever the length or flexibility of the neck, the number of vertebrae is the same, viz., seven, with only three known exceptions, the Manatee and Hoffman’s Two-toed Sloth (Choloepus ho ff manni), which both have but six, and the Three-toed Sloth (Bradypus tridactylus), which has nine, though in this case the last two usually support movable ribs, though not sufficiently developed to reach the sternum.

The dorsal (or thoracic, as it would be more correctly termed) region consists of the vertebrae which succeed those of the neck, having ribs movably articulated to them. These ribs arch round the thorax,—the anterior one, and most usually the greater number of those that follow, being attached below to the sternum.

The lumbar region consists of those vertebrae of the trunk in front of the sacrum which bear no movable ribs. It may happen that, as the ribs decrease in size posteriorly, the last being sometimes more or less rudimentary, the step from the thoracic to the lumbar region may be gradual and rather undetermined in a given species. But most commonly this is not the case, and the distinction is as well defined here as in any other region. As a general rule there is a certain relation between the number of the thoracic and lumbar vertebrae, the whole number being tolerably constant in a given group of animals, and any increase of the one being at the expense of the other. Thus in all known Artiodactyle Ungulata there are 19 dorso-lumbar vertebrae; but these may consist of 12 dorsal and 7 lumbar vertebrae, or 13 dorsal and 6 lumbar, or 14 dorsal and 5 lumbar. The smallest number of dorso-lumbar vertebrae in mammals occurs in some Armadillos, which have but 14. The number found in Man, the higher Apes, and most Bats, viz., 17, is exceptionally low 19 prevails in the Artiodactyles, nearly all Marsupials, and very many Rodents; 20 or 21 in Carnivora and most Insectivora; and 23 in Perissodactyla. The highest and quite exceptional numbers are in the Two-toed Sloth (Choloepus) 27, and the Hyrax 30. The prevailing number of rib-bearing vertebrae is 12 or 13, any variation being generally in excess of these numbers.

The sacral region offers more difficulties of definition. Taking the human “os sacrum” for a guide for comparison, it is generally defined as consisting of those vertebrae between the lumbar and caudal regions which are ankylosed together to form a single bone. It happens, however, that the number of such vertebrae varies in different individuals of the same or nearly allied species, especially as age advances, when a certain number of the tail vertebrae generally become incorporated with the true sacrum. Other suggested-tests, as those vertebrae which have a distinct additional (pleurapophysial) centre of ossification between the body and the ilium, those to which the ilium is directly articulated, or those in front of the insertion of the ischio-sacral ligaments, being equally unsatisfactory or unpractical, the old one of ankylosis, as it is found to prevail in the average condition of adults in each species, is used in the enumeration of the vertebrae in the following pages. The Cetacea, having no iliac bones, have no part of the vertebral column modified into a sacrum.

The caudal vertebrae are those placed behind the sacrum, and terminating the vertebral column. They vary in number greatly,—being reduced to 5, 4, or even 3, in a most rudimentary condition, in Man and in some Apes and Bats, and being numerous and powerfully developed, with strong and complex processes, in many mammals, especially among the Edentata, Cetacea, and Marsuρialia. The highest known number, 46, is possessed by the African Long-tailed Manis. Connected with the under surface of the caudal vertebrae of many mammals which have the tail well developed are certain bones formed more or less like an inverted arch, called chevron bones, or by the French os en V. These are always situated nearly opposite to an intervertebral space, and are generally articulated both to the vertebra in front and the vertebra behind, but sometimes chiefly or entirely either to one or the other.

The sternum of mam mals is a bone, or generally a series of bones, placed longitudinally in the mesial line, on the inferior or ventral aspect of the thorax, and connected on each side with the vertebral column by a series of more or less ossified bars called “ribs.” It is present in all mammals, but varies much in character in the different groups. It usually consists of a series of distinct segments placed one before the other, the anterior being called the presternum or “manubrium sterni” of human anatomy, and the posterior the xiphisternum, or xiphioid or ensiform process, while the intermediate segments, whatever their number, constitute the mesosternum or “body.” In the Whalebone Whales the presternum alone is developed, and but a single pair of ribs is attached to it.

The ribs form a series of long, narrow, and more or less flattened bones, extending laterally from the sides of the vertebral column, curving downwards towards the median line of the body below, and mostly joining the sides of the sternum. The posterior ribs, however, do not directly articulate with that bone, but are either attached by their extremities to the edges of each rib in front of them, and thus only indirectly join the sternum, or else they are quite free below, meeting·no part of the skeleton. These differences have given rise to the division into “true” and “false” ribs (by no means good expressions), signifying those that join the sternum directly and those that do not; and of the latter, those that are free below are called “floating” ribs. The portion of each rib nearest the vertebral column and that nearest the sternum differ in their characters, the latter being usually but imperfectly ossified, or remaining permanently cartilaginous. These are called “costal cartilages,” or when ossified “sternal ribs.”

In the anterior part of the thorax the vertebral extremity of each rib is divided into two parts, “bead” and “tubercle”; the former is attached to the side of the body of the vertebra, the latter to its transverse process; the former attachment corresponds to the interspace between the vertebrae, the head of the rib commonly articulating partly with the hinder edge of the body of the vertebra antecedent to that which bears its tubercle. Hence tho body of the last cervical vertebra usually supports part of the head of the first rib.

In the posterior part of the series the capitular and tubercular attachments commonly coalesce, and the rib is attached solely to its corresponding vertebra. The number of pairs of ribs is of course the same as that of the thoracic vertebrae.

The appendicular portion of the framework consists, when completely developed, of two pairs of limbs, anterior and posterior.

The anterior limb is present and fully developed in all mammals, being composed of a shoulder girdle and three segments belonging to the limb proper, viz., the upper arm or brachium, the fore-arm or antibrachium, and the hand or manus.

The shoulder girdle in the large majority of mammals is in a rudimentary or rather modified condition, compared to that in which it exists in other vertebrates. In the Monotremata (Ornithorhynchus and Echidna') alone is the ventral portion, or coracoid, complete and articulates with the sternum below, as in the Sauropsida. In all other mammals this portion, though ossified from a distinct centre, forms only a process, sometimes a scarcely distinct tubercle, projecting from the anterior border of the glenoid cavity of the scapula. The last-named bone is always well developed, generally broad and flat (whence its vernacular name “blade bone ”), with a ridge called the “spine” on its outer surface, generally ending in a free curved process, the “acromion.” As the scapula affords attachment to many of the muscles which act upon the anterior limb, its form and the development of its processes are greatly modified according to the uses to which the member is put. It is most reduced and simple in character in those animals whose limbs are mere organs of support, as the Ungulates, and most complex when they are also used for grasping, climbing, or digging. The development or absence of the clavicle or “collar-bone,” an accessory bar which connects the sternum with the scapula and steadies the shoulderjoint, has a somewhat similar relation, though its complete absence in the Bears shows that this is not an invariable rule. A complete clavicle is found in Man and all the Primates, in Chiroptera, all Insectivora (except Potamogale), in many Rodents, in most Edentates, and in all Marsupials, except Perameles. More or less rudimentary clavicles (generally suspended freely in the muscles) are found in the Cat, Dog, and most Carnivora, Myrmecophaga, and some Rodents. Clavicles are altogether absent in most of the Ursids,, all the Pinnipedia, Manis among Edentates, the Cetacea, Sirenia, Proboscidea, all Ungulates, and some Rodents.

The proximal segment of the limb proper contains a single bone, the humerus, and the second segment two bonis, the radius and the ulna, placed side by side, articulating with the humerus at their proximal, and with the carpus at their distal extremity. In their primitive and unmodified condition these bones may be considered as placed one on each border of the limb, the radius being preaxial or anterior, and the ulna postaxial or posterior, when the distal or free end of the limb is directed outwards or away from the trunk. This is their position in the earliest embryonic condition, and is best illustrated in adult mammals in the Cetacea, where the two bones are fixed side by side and parallel to each other. In the greater number of mammals the bones assume a very modified and adaptive position, usually crossing each other in the forearm, the radius in front of the ulna, so that the preaxial bone (radius), though external (in the ordinary position of the limb) at the upper end, is internal at the lower end; and the hand, being mainly fixed to the radius, also has its preaxial border internal. In the large majority of mammals the bones are fixed in this position, but in some few, as in Man, a free movement of crossing and uncrossing—or pronation and supination, as it is termed—is allowed between them, so that they can be placed in their primitive parallel condition, when the hand (which moves with the radius) is said to be supine, or they may be crossed, when the hand is said to be prone.

In most mammals which walk on four limbs, and in which the hand is permanently prone, the ulna is much reduced in size, and the radius increased, especially at the upper end; and the articular surface of the latter, instead of being confined to the external side of the trochlea of the humerus, extends all across its anterior surface, and the two bones, instead of being external and internal, are anterior and posterior. In many hoofed or ungulated mammals, and in Bats, the ulna is reduced to little more than its upper articular extremity, and firmly ankylosed to the radius,—stability of these parts being more essential than mobility.

The terminal segment of the anterior limb is the hand or manus. Its skeleton consists of three divisions :—(1) the “carpus,” a group of small, more or less rounded or angular bones with flattened surfaces applied to one another, and, though articulating by synovial joints, having scarcely any motion between them; (2) the “metacarpus,” a series of elongated bones placed side by side, with their proximal ends articulating by almost immovable joints with the carpus;

(3) the “phalanges” or bones of the digits, usually three in number to each, articulating to one another by freely movable hingejoints, the first being connected in like manner to the distal end of the corresponding metacarpal bone.

To understand thoroughly the arrangement of the bones of the carpus in mammals, it is necessary to study their condition in some of the lower vertebrates. Fig. 11 represeùts the manus in one of its most complete and at the same time most generalized forms, as seen in one of the Water Tortoises (Chelydra serpentina). The carpus consists of two principal rows of bones. The upper or proximal row contains three bones, to which Gegenbaur has applied the terms radiale (r), intermedium, (t), and ulnare (u), the first being on the radial or preaxial side of the limb. The lower or distal row contains five bones, called carpale 1, 2, 3, 4, and 5 respectively, commencing on the radial side’ Between these two rows, in the middle of the carpus, is a single bone, the centrale (c). In this very symmetrical carpus it will be observed that the radiale supports on its distal side two bones, carpale 1 and 2; the intermedium is in a lino with the centrale and carpale 3, which together form a median axis of the hand, while the ulnare has also two bones articulated with its distal end, viz., carpale 4 and 5. Each of the carpals of the distal row supports a metacarpal.

In the carpus of the Mammalia there are usually two additional bones developed in the tendons of the flexor muscles, one on each side of the carpus, which may be called the radial and ulnar sesamoid bones; the latter is most constant and generally largest, and is commonly known as the pisiform bone. The fourth and fifth carpals of the distal rows are always united into a single bone, and the centrale is very often absent. As a general rule all the other bones are present and distinct, though it not unfrequently happens that one or more may have coalesced to form a single bone, or may be altogether suppressed.

The following table shows the principal names in use for the various carpal bones,—those in the second column being the terms most generally employed by English anatomists :— [table]

The metacarpal bones, with the digits which they support, are never more than five in number, and are described numerically—first, second, &c., counting from the radial towards the ulnar side. The digits are also sometimes named (1) the pollex, (2) index, (3) medius, (4) annularis, (5) minimus. One or more may be in a rudimentary condition, or altogether suppressed. If one is absent, it is most commonly the first. Excepting the Cetacea, no mammals have more than three phalanges to each digit, but they may occasionally have fewer by suppression or ankylosis. The first or radial digit is an exception to the usual rule, one of its parts being constantly absent, for, while each of the other digits has commonly a metacarpal and three phalanges, it has only three bones altogether; whether the missing one is a metacarpal or one of the phalanges is a subject which has occasioned much discussion, and has not yet been satisfactorily decided. The terminal phalanges of the digits are usually specially modified to support the nail, claw, or hoof, and are called “ungual phalanges.” In walking, some mammals (as the Bears) apply the whole of the lower surface of the carpus, metacarpus, and phalanges to the ground; to these the term “plantigrade” is applied. Many others (as nearly all the Ungulata') only rest on the last one or two phalanges of the toes, the first phalanx and the metacarpals being vertical and in a line with the fore-arm. These are called “digitigrade.” Intermediate conditions exist between these two forms, to which the terms “phalangigrade” (as the Camel) and “subplantigrade,” (as in most Carnivora) are applied. When the weight is borne entirely on the distal surface of the ungual phalanx, and the horny structures growing around it, as in the Horse, the mode of progression is called “unguligrade.”

In the Chiroptera the digits are enormously elongated, and support a cutaneous expansion constituting the. organ of flight. In the Cetacea the manus is formed into a paddle, being covered by continuous integument, which conceals all trace of division into separate digits, and without sign of nails or claws. In the Sloths the manus is long and very narrow, habitually curved, and terminating in two or three pointed curved claws in close apposition with each other, incapable, in fact, of being divaricated, so that it is reduced to the condition of a hook, by which the animal suspends itself to the boughs of the trees among which it lives. These are only examples of the endless modifications to which the distal extremity of the limb is subjected in adaptation to the various purposes to which it is applied.

The posterior limb is constructed upon a plan very similar to that of the anterior extremity. It consists of a pelvic girdle and three segments belonging to the limb proper, viz., the thigh, the leg, and the foot or ρes.

The pelvic girdle is present in some form in all mammals, though in the Cetacea and the Sirenia it is in an exceedingly rudimentary condition. In all mammals except those belonging to the two orders just named, each lateral half of the pelvic girdle consists essentially, like the corresponding part of the anterior limb, of a flattened rod of bone crossing the long axis of the trunk, having an upper or dorsal and a lower or ventral end. The upper end diverges from that of the opposite side, but the lower end approaches, and, in most cases, meets it, forming a symphysis, without the intervention of any bone corresponding to the sternum. The pelvic girdle differs from the shoulder girdle in being firmly articulated to the vertebral column, thus giving greater power to the hinder limb in its function of supporting and propelling the body. Like the shoulder girdle, it bears on its outer side, near the middle, a cup-shaped articular cavity (“acetabulum ”), into which the proximal end of the first bone of the limb proper is received. Each lateral half of the girdle is called the “os innominatum,” and consists originally of three bones which unite at the acetabulum. The “ilium” or upper bone is that which articulates with the sacral vertebrae. Of the two lower bones the anterior or “pubis” unites with its fellow of the other side at the symphysis; the posterioris the “ischium.” These two form two bars of bone, united above and below, but leaving a space between them in the middle, filled only by membrane, and called the “thyroid” or “obturator” foramen. The whole circle of bone formed by the two innominate bones and the sacrum is called the pelvis. In the Monotremata and Marsupial·ia, a pair of thin, flat, elongated bones called epipubic or marsupial bones are attached to the fore part of the pubis, and project forward into the muscular wall of the abdomen.

The first segment of the limb proper has one bone, the femur, corresponding with the humerus of the upper limb. The second segment has two bones, the tibia and fibula, corresponding with the radius and ulna. These bones always lie in their primitive unmodified position, parallel to each other, the tibia on the preaxial and the fibula on the postaxial side, and are never either permanently crossed or capable of any considerable amount of rotation, as in the corresponding bones of the fore limb. In the ordinary walking position the tibia is internal, and the fibula external. In many mammals the fibula is in a more or less rudimentary condition, and it often ankyloses with the tibia at one or both extremities. The patella or “kneecap” is found in an ossified condition in all mammals, with the exception of some of the Marsupialia. It is a large sesamoid bone developed in the tendon of the extensor muscles of the thigh, where the tendon passes over the front of the knee-joint, to which it serves as a protection. There are frequently smaller ossicles, one or two in number, situated behind the femoral condyles, called “fabellae.”

The terminal segment of the hind limb is the foot or pes. Its skeleton presents in many particulars a close resemblance to that of the manus, being divisible into three parts :—(1) a group of short, more or less rounded or square-shaped bones, constituting the tarsus; (2) a series of long bones placed side by side, forming the metatarsus; and (3) the phalanges of the digits or toes.

The bones of the tarsus of many of the lower Vertebrata closely resemble both in number and arrangement those of the carpus, as shown in fig. 11. They have been described in their most generalized condition by Gegenbaur under the names expressed in the first column of the following table. The names in the second column are those by which they are most generally known to English anatomists, while in the third column some synonyms occasionally employed are added [table]

The bones of the tarsus of mammals present fewer diversities of number and arrangement than those of the carpus. The proximal row (see fig. 12) always consists of two bones, the astragalus (a, which probably represents the coalesced scaphoid and lunar of the hand) and the calcaneum (c). The former is placed more to the dorsal side of the foot than the latter, and almost exclusively furnishes the tarsal part of the tibio-tarsal or ankle-joint. The calcaneum, placed more to the ventral or “plantar” side of the foot, is elongated backwards to form a more or less prominent tuberosity, the “tuber calcis,” to which the tendon of the great extensor muscles of the foot is attached. The navicular bone (n) is interposed between the proximal and distal row on the inner or tibial side of the foot, but on the outer side the bones of the two rows come into contact. The distal row, when complete, consists of four bones, which, beginning on the inner side, are the three cuneiform bones, internal (c 1 ), middle (c 2 ), and external (c 3 ), articulated to the distal surface of the navicular, and the cuboid (cδ), articulated with the calcaneum. Of these the middle cuneiform is usually the smallest in animals in which all five digits are developed; but when the hallux is wanting the internal cuneiform may be rudimentary or altogether absent. The three cuneiform bones support respectively the first, second, and third metatarsals, and the cuboid supports the fourth and fifth; they thus exactly correspond with the four bones of the distal row of the carpus.

In addition to these constant tarsal bones, there may be supplemental or sesamoid bones :—one situated near the middle of the tibial side of the tarsus, largely developed in many Carnivora and Rodentia ; another, less frequent, on the fibular side; and a third, often developed in the tendons of the plantar surface of the tarsus, is especially large in Armadillos. There is also usually a pair of sesamoid bones on the plantar aspect of each metatarso-phalangeal articulation.

The metatarsal bones never exceed five in number, and the phalanges follow the same numerical rule as in the manus, never exceeding three in each digit. Moreover, the first digit, counting from the tibial side, or hallux, resembles the pollex of the haud in always having one segment less than the other digits. As the function of the hind foot is more restricted than that of the hand, the modifications of its structure are less striking. In the Cetacea and the Sirenia it is entirely wanting, though in some members of the first-named order rudiments of the bones of the first and second segment of the limb have been detected.

Digestive System.

The search after the purpose which every modification of structure subserves in the economy is always full of interest, and, if conducted with due caution and sufficient knowledge of all the attendant circumstances, may lead to important generalizations. It must always be borne in mind, however, that adaptation to its special function is not the only cause of the particular form or structure of an organ, but that this form, having in all probability been arrived at by the successive and gradual modification of some other different form from which it is now to a greater or less degree removed, has other factors besides use to be taken into account. In no case is this principle so well seen as in that of the organs of digestion. These may be considered as machines which have to operate upon alimentary substances in very different conditions of mechanical and chemical combination, and to reduce them in every case to the same or precisely similar materials; and we might well imagine that the apparatus required to produce flesh and blood out of coarse fibrous vegetable substances would be different from that which had to produce exactly the same results out of ready-made flesh or blood; and in a very broad sense we find that this is so. If we take a large number of carnivorous animals, belonging to different fundamental types, and a large number of herbivorous animals, and strike a kind of average of each, we shall find that there is, pervading the first group, a general style, if we may use the expression, of the alimentary organs, different from that of the others. There is a specially carnivorous and a specially herbivorous modification of these parts. But, if function were the only element which has guided such modification, it might be inferred that, as one form must be supposed to be best adapted and most perfect in its relation to a particular kind of diet, that form would be found in all the animals consuming that diet. But this is far from being the case. The Horse and the Ox, for instance,—two animals whose food in the natural state is precisely similar,—are yet most different as regards the structure of their alimentary canal, and the processes involved in the preparation of that food. Again, the Seal and the Porpoise, both purely fish-eaters, which seize and swallow and digest precisely the same kind of prey in precisely the same manner, have a totally different arrangement of the alimentary canal. If the Seal’s stomach is adapted in the best conceivable manner for the purpose it has to fulfil, why is not the Porpoise’s stomach an exact facsimile of it, and vice versa? We can only answer, the Seal and Porpoise belong to different natural groups of animals, formed on different primitive types, or descended from differently constructed ancestors. On this principle only can we account for the fact that, whereas, owing to the comparatively small variety of the different alimentary substances met with in nature, few modifications would appear necessary in the organs of digestion, there is really endless variety in the parts devoted to this purpose.

The digestive apparatus of mammals, as in other vertebrates, consists mainly of a tube with an aperture placed at or near either extremity of the body,—the oral and the anal orifice,—with muscular walls, the fibres of which are so arranged as by their regular alternate contraction and relaxation to drive onwards the contents of 1 the tube from the first to the last of these apertures. The 1 anterior or commencing portion of this tube and the parts around it are greatly and variously modified in relation to the functions assigned to them of selecting and seizing the food, and preparing it by various mechanical and chemical processes for the true digestion which it has afterwards to undergo before it can be assimilated into the system. For this end it is dilated into a chamber or cavity called the mouth, bordered externally by the lips, usually muscular and prehensile, and supported by a movable framework which carries the teeth,—organs the structure and modifications of which have been already described. The roof of the mouth is formed by the palate, terminating behind by a muscular, contractile arch, having in Man and some few other species a median projection called uvula, beneath which the mouth communicates with the pharynx. The anterior part of the palate is composed of mucous membrane tightly stretched over the flat or slightly concave bony lamina which separates the mouth from the nasal passages, and is generally raised into a series of transverse ridges, which sometimes, as in Ruminants, attain a considerable development. In the floor of the mouth, between the rami of the mandible, and supported behind by the hyoidean apparatus, lies the tongue, an organ the free surface of which, especially in its posterior part, is devoted to the sense of taste, but which also by its great mobility, being composed almost entirely of muscular fibres, performs important mechanical functions connected with masticating and procuring food. Its modifications of form in different mammals are very numerous. Between the long, extensile, vermiform tongue of the Anteaters, which is essential to the peculiar mode of feeding of those animals, and the short, sessile, and almost functionless tongue of the Porpoise, every intermediate condition is found. Whatever the form, the upper surface is always covered with numerous fine papillae, in which the terminal filaments of the gustatory nerve are distributed.

In connexion with the buccal cavity is an extensive and complex glandular apparatus which pours its secretions into it—secretions which constitute the fluid commonly known as saliva. This apparatus consists of small glands embedded in the mucous membrane or submucous tissue lining the cavity of the mouth, and which are of two kinds (the follicular and the racemose), and of others in which the secreting structure is aggregated in distinct masses removed some distance from the cavity, other tissues besides the lining membrane being usually interposed, and pouring their secretion into the cavity by a distinct tube or duct, which traverses the mucous membrane. To the latter alone the name of “salivary glands” is ordinarily appropriated, although the distinction between them and the smaller racemose glands is only one of convenience for descriptive purposes, their structure being more or less identical; and, as the fluids secreted by all become mixed in the mouth, their functions are, at all events in great part, common. Under the name of salivary glands are commonly included —(1) the “parotid,” situated very superficially on the side of the head, below or around the cartilaginous external auditory meatus, and the secretion of which enters the mouth by a duct (often called Steno’s or Stenson’s) which crosses the masseter muscle and opens into the upper and back part of the cheek; and (2) the “submaxillary,” situated in the neck, near or below the angle of the mandible, and sending a long duct (Wharton’s) forwards to open in the fore-part of the floor of the cavity of the mouth, below the apex of the tongue. These are the most largely developed and constant of the salivary glands, being met with in various degrees of development in almost all animals of the class. Next in constancy are (3) the “sublingual,” closely associated with the last-named, at all events in the locality in which the secretion is poured out; and (4) the “zygomatic,” found only in some animals in the cheek, just under cover of the anterior part of the zygomatic arch, its duct entering the buccal cavity near that of the parotid.

The most obvious function common to the secretion of these various glands, and to that of the smaller ones placed in the mucous membrane of the lips, the cheeks, the tongue, the palate and fauces, is the mechanical one of moistening and softening the food, to enable it the more readily to be tasted, masticated, and swallowed, though each kind of gland may contribute in different manner and different degree to perform this function. The saliva is, moreover, of the greatest importance in the first stage or introduction to the digestive process, as it dissolves or makes a watery extract of all soluble substances in the food, and so prepares them to be further acted on by the more potent digestive fluids met with subsequently in their progress through the alimentary canal. In addition to these functions it seems now well established by experiment that saliva serves in Man and many animals to aid directly in the digestive process, particularly by its power of inducing the saccharine transformation of amylaceous substances. As a general rule, in mammals the parotid saliva is more watery in its composition, while that of the submaxillaries, and still more the sublingual, contains more solid elements and is more viscid, so much so that some anatomists consider the latter, together with the small racemose glands of the cheeks, lips, and tongue, as mucous glands, retaining the name of salivary only for the parotid. These peculiar properties are sometimes illustrated in a remarkable degree, as, for example, the great secretion of excessively viscid saliva which lubricates the tongue of the Anteaters and Armadillos, associated with enormously developed submaxillary glands; while, on the other hand, the parotids are of great size in those animals which habitually masticate dry and fibrous food.

After the preparation which the aliment has undergone in the mouth,—the extent of which varies immensely in different forms, being reduced almost to nothing in such animals as the Seals and Cetaceans, which, to use the familiar expression, “bolt” their food entire,—it is swallowed, and is carried along the oesophagus by the action of its muscular coats into the stomach. In the greater proportion of mammals this’ organ is a simple saccular dilatation of the alimentary canal, but in others it undergoes remarkable modifications and complexities. The lining of the stomach is thickly beset with tubular glands, which are generally considered to belong to two different forms, recognizable by their structure, and different in their function—the most numerous and important secreting the gastric juice (the active agent in stomachic digestion), and hence called “peptic” glands, the others concerned only in the elaboration of mucus. The relative distribution of these glands in different regions of the walls of the stomach varies greatly in different animals, and in many species there are large tracts of the mucous membrane which do not secrete a fluid having the properties of gastric juice, and often constitute more or less distinct cavities devoted to storing and perhaps softening or otherwise preparing the food for digestion. Sometimes there is a great aggregation of glands forming distinct thickened patches of the stomach wall, as in the Beaver and Koala, or even collected in pyriform pouches with a common narrow opening into the cavity, as in the Manatee and the curious African Rodent Lophyomys. The action of the gastric fluid is mainly exerted upon the nitrogenous elements of the food, which it dissolves and modifies so as to render them capable of undergoing absorption, which is partly effected by the blood-vessels of the stomach, though the greater part passes through the pylorus, an aperture surrounded by a circular muscular valve, into the intestinal canal. Here it comes in contact with the secretion of a vast number of small glands called the crypts of Lieberkuhn, somewhat similar to those of the stomach, and also of several special glands of a different character, namely, the small racemose, duodenal, or Brunner’s glands, the pancreas, and the liver.

The intestinal canal varies greatly in relative length and capacity in different animals, and it also offers manifold peculiarities of form, being sometimes a simple cylindrical tube of nearly uniform calibre throughout, but more often subject to alterations of form and capacity in different portions of its course,—the most characteristic and constant being the division into an upper and narrower and a lower and wider portion, called respectively the small and the large intestine, the former being divided quite arbitrarily and artificially into duodenum, jejunum, and ileum, and the latter into colon and rectum. One of the most striking peculiarities of this part of the alimentary canal is the frequent presence of a diverticulum or blind pouch, the caput caecum coli, as it was first called, a name generally abbreviated into “caecum,” situated at the junction of the large and the small intestine, a structure presenting an immense variety of development, from the smallest bulging of a portion of the side wall of the tube to a huge and complex sac, greatly exceeding in capacity the remainder of the alimentary canal. It is only in herbivorous animals that the caecum is developed to this great extent, and among these there is a curious complementary relationship between the size and complexity of the organ and that of the stomach. Where the latter is simple the caecum is generally the largest, and vice versa. Both caecum and colon are often sacculated, a disposition caused by the arrangement of the longitudinal bands of muscular tissue in their walls; but the small intestine is always smooth and simple-walled externally, though its lining membrane often exhibits various contrivances for increasing the absorbing surface without adding to the general bulk of the organ, such as the numerous small villi by which it is everywhere beset, and the more obvious transverse, longitudinal, or reticulating folds projecting into the interior, met with in many animals, of which the “valvulae conniventes” of Man form well-known examples. Besides the crypts of Lieberkuhn found throughout the intestinal canal, and the glands of Brunner confined to the duodenum, there are other structures in the mucous membrane, about the nature of which there is still much uncertainty, called “solitary” and “agminated” glands, the latter more commonly known by the name of “Peyer’s patches.” These were formerly supposed to be secretory organs, which discharged some kind of fluid into the intestine, but are now more generally considered to belong to the group of structures of somewhat mysterious function of which the lymphatic and lacteal glands are members. The solitary glands are found scattered irregularly throughout the whole intestinal tract; the agminated, on the other hand, are always confined to the small intestine, and are most abundant in its lower part. They are subject to great variation in number and in size, and even in different individuals of the same species, and also differ in character at different periods of life, becoming atrophied in old age.

The distinct glands situated outside of the walls of the intestinal canal, but which pour their secretion into it, are the pancreas and the liver. The latter is the most important on account of its size, if not on account of the direct action of its secretion in the digestive process. This large gland, so complex in structure and function, is well developed in all mammals, and its secreting duct, the bile duct, always opens into the duodenum or that portion of the canal which immediately succeeds the stomach. It is situated in the right side of the abdomen in contact with the diaphragm and the stomach, but varies greatly in relative size, and also in form, in different groups of mammals. In most mammals a gall-bladder, consisting of a pyriform diverticulum from the gall duct, is present, but in many it is wanting, and it is difficult to find the rationale of its presence or absence in relation to use or any other circumstance in the animal economy.

The descriptions of the livers of various animals to be· met with in treatises or memoirs on comparative anatomy are very difficult to understand for want of a uniform system of nomenclature. The difficulty usually met with arises from the circumstance that this organ is divided sometimes, as in Man, Ruminants, and the Cetacea, into two main lobes, which have been always called respectively right and left, and in other cases, as in the lower Monkeys, Carnivora, Insectivora, and many other orders, into a larger number of lobes. Among the latter the primary division usually appears at first sight tripartite, the whole organ consisting of a middle, called “cystic” or “suspensory” lobe, and two lateral lobes, called respectively right and left lobes. This introduces confusion in describing livers by the same terms throughout the whole series of mammals, as the right and left lobes of the Monkey or Dog, for instance, do not correspond with parts designated by the same name in Man and the Sheep. There are, moreover, conditions in which neither the bipartite nor the tripartite system of nomenclature will answer, which we should have considerable difficulty in describing without some more general system. In order to arrive at such a system it appears desirable to consider the liver in all cases as primarily divided by the umbilical vein (seefig.14, u) into two segments, right and left. This corresponds with its development and with the condition characteristic of the organ in the inferior classes of vertebrates. The situation of this division can almost always be recognized in adult animals by the persistence of some traces of the umbilical vein in the form of the round ligament, and by the position of the suspensory ligament.

When the two main parts into which the liver is thus divided are entire, as in Man, the Ruminants, and Cetacea, they may be spoken of as the right and left lobes; when fissured, as the right and left segments of the liver, reserving the term lobe for the subdivisions. This will involve no ambiguity, for the terms right and left lobe will no longer be used for divisions of the more complex form of liver. In the large majority of mammals each segment is further divided by a fissure, more or less deep, extending from the free towards the attached border, which are called right and left lateral fissures (fig. 14, rlf and Ilf). When these are more deeply cut than the umbilical fissure («), the organ has that tripartite or trefoil-like form just spoken of, but it is easily seen that it is really divided into four regions or lobes, those included between the lateral fissures being the right and left central (re and lc) separated by the umbilical fissure, and those beyond the lateral fissures on each side being the right and left lateral lobes (rl and ll). The essentially bipartite character of the organ and its uniformity of construction throughout the class are thus not lost sight of, even in the most complex forms. The left segment of the liver is rarely complicated to any further extent, except in some cases by minor or secondary fissures marking off small lobules, generally inconstant and irregular, and never worthy of any special designation. On the other hand, the right segment is usually more complex. The gall bladder, when present, is always attached to the under surface of the right central lobe, sometimes merely applied to it, in other cases deeply embedded in its substance. In many cases the fossa in which it is sunk is continued to the free margin of the liver as an indent, or even a tolerably deep fissure (cf). The portal fissure (p), through which the portal vein and hepatic artery enter and the gall duct emerges from the liver, crosses this lobe transversely, near the attached border of the liver. The right lateral lobe always has the great vena cava (yc) either grooving its surface or tunnelling through its substance near the inner or left end of its attached border; and a prolongation of the lobe to the left, between the vein and the portal fissure, sometimes a mere flat track of hepatic substance, but more often a prominent tongue-shaped process, is the so-called “Spigelian lobe ”(s). From the under surface of the right lateral lobe a portion is generally partially detached by a fissure, and called the “caudate lobe” (c). In Man this is almost obsolete, but in most mammals it is of considerable magnitude, and has very constant and characteristic relations. It is connected by an isthmus at the left (narrowest or attached) end to the Spigelian lobe, behind which isthmus the vena cava is always in relation to it, channelling through or grooving its surface. It generally has a pointed apex, and is deeply hollowed to receive the right kidney, to the upper and inner side of which it is applied.

Considerations derived from the comparatively small and simple condition of the liver of the Ungulates, compared with its large size and complex form in the Carnivora, have led to the perhaps too hasty generalization that the first type is related to a herbivorous and the latter to a carnivorous diet. The exceptions to such a proposition are very numerous. The fact of the great difference between the liver of the Cetacea and that of the Seals cannot be accounted for by difference of habits of life, though it perhaps may be by difference of origin, upon the supposition that the former are modifications of the primary branch of mammals from which the Ungulates, and the latter of that from which the Carnivora, are derived. Circulatory, Absorbent, Respiratory, and Urinary Systems.

The blood - of mammals is always red, and during the life of the animal hot, having a nearly uniform temperature, varying within a few degrees on each side of 100° Fahr. The corpuscles are, as usual in vertebrates, of two kinds: —(1) colourless, spheroidal, nucleated, and exhibiting amoeboid movements; while (2) the more numerous, on which depends the characteristic hue of the fluid in which they are suspended, are coloured, non-nucleated, flattened, slightly biconcave disks, with circular outline in all known species except the Camels and Llamas, where they have the elliptical form characteristic of the red corpuscles of nearly all the other vertebrates, though adhering to the mammalian type in absence of nucleus and relatively small size. As a rule they are smaller as well as more numerous than in other classes, but vary considerably in. size in different species, and not always in relation to the magnitude of the animal, a Mouse, for instance, having as large corpuscles as a Horse. Within the limits of any natural group there is, however, very often some such relation, the largest corpuscles being found among the large species and the smallest corpuscles among the small species of the group, but even to this generalization there are many exceptions. The transverse diameter of the red corpuscles in Man averages ∙ 5 ^ 1 θ < 5 - of an inch, which is exceptionally large, and only exceeded by the Elephant (ytït)» anc ∣∙ b y some Cetacea and Edentata. They are also generally large in Apes, Rodents, and the Monotremata, and small in the Artiodactyles, least of all in the Chevrotains (Trag ulus), being in T. javanicus and meminna not more than -rasa⅛.

The heart of mammals consists of four distinct cavities, two auricles and two ventricles. Usually the ventricular portion is externally of conical form, with a simple apex, but in the Sirenia it is broad and flattened, and a deep notch separates the apical portion of each ventricle. A tendency to this form is seen in the Cetacea and the Seals. It is characteristic of mammals alone among vertebrates that the right auriculo-ventricular valve is tendinous like the left, consisting of flaps held in their place by fibrous ends (chordae tendiniae) which arise from projections from the muscular walls of the ventricular cavity (musculi papillares'). In the Monotremata a transition between this condition and the simple muscular flap of the Sauropsida is observed. In most of the larger Ungulates a distinct but rather irregular ossification is developed in the central tendinous portion of the base of the heart.

The orifices of the aorta and pulmonary artery are each guarded by three semilunar valves. The aorta is single, and arches over the left bronchial tube. After supplying the tissues of the heart itself with blood by means of the coronary arteries, it gives off large vessels (“carotid ”) to the head and (“brachial”) to the anterior extremities. The mode in which these vessels arise from the aorta varies much in different mammals, and the study of their disposition affords some guide to classification. In nearly all cases the right brachial and carotid have a common origin (called “innominate artery” in anthropotomy). The other two vessels may come off from this, as is the rule in Ungulates, the common trunk constituting the “anterior aorta” of veterinary anatomy; or they may be detached in various degrees, both arising separately from the aorta, as in Man, or the left carotid from the innominate and the left brachial from the aorta, a very common arrangement, or the last two from a common second or left innominate as in some Bats and Insectivores. The aorta, after giving off the intercostal arteries, passes through the diaphragm into the abdomen, and, after supplying the viscera of that cavity by means of the gastric, hepatic, splenic, mesenteric, renal, and spermatic vessels, gives off in the lumbar region a large branch (iliac) to each of the hinder extremities, which also supplies the pelvic τisc⅛ra, and is continued onwards in the middle line, greatly diminished in size, along the under surface of the tail. In certain mammals, arterial plexuses, called retia mirabilia, formed by the breaking up of the vessel into an immense number of small trunks, which may run in a straight course parallel to one another (as in the limbs of Sloths and Slow Lemurs), or form a closely packed network, as in the intracranial plexuses of Ruminants, or a sponge-like mass of convoluted vessels, as in the intercostale of Cetaceans, are peculiarities of the vascular system the meaning of which is not in all cases clearly understood. In the Cetaced they are obviously receptacles for containing a large quantity of oxygenated blood available during the prolonged immersion, with consequent absence of respiration, to which these animals are subject.

The vessels which return the blood to the heart from the head and upper extremities usually unite, as in Man, to form the single vena cava superior or precaval vein, but in some Insectivores, Chiroptera, and Rodents, and in the Elephant, and all Marsupials and Monotremes, the two superior caval veins enter the right auricle without uniting, as in birds. In Seals and some other diving mammals there is a large venous sinus or dilatation of the inferior cava immediately below the diaphragm. In the Cetacea the purpose of this is supplied by the immense abdominal venous plexuses. As a rule the veins of mammals are furnished with valves, but these are said to be altogether wanting in the Cetacea, and in the superior and inferior cava, subclavian and iliac veins, the veins of the liver (both portal and hepatic), heart, lungs, kidneys, brain, and spinal chord of other mammals. Many of the veins within the cranium are included in spaces formed by the separation of the laminae of the dura mater, and do not admit of being dilated beyond a certain size; these are termed sinuses. The portal circulation in mammals is limited to the liver, the portal vein being formed by the superior and inferior mesenteric, the splenic, the gastroepiploic, and the pancreatic veins. The kidney is supplied solely by arterial blood, and its veins empty their contents only into the inferior cava.

The absorbent or lymphatic system of vessels is very completely developed in the Mammalia. Its ramifications extend through all the soft tissues of the body, and convey a colourless fluid called lymph, containing nucleated corpuscles, and also, during the process of digestion, the chyle, a milky fluid taken up by the lymphatics (here called lacteals) of the small intestine, and pour them into the general vascular system, where they mix with the venous blood. The lymphatic vessels of the hinder extremities, as well as those from the intestinal canal, unite in the abdomen to form the “thoracic duct,” the hinder end or commencement of which has a dilatation called the receptaculum chyli. The duct, which is of irregular size and sometimes double, often dividing and uniting again in its course, or even becoming plexiform, passes forwards close to the bodies of the thoracic vertebrae, and empties itself, by an orifice guarded by a valve, into the great left brachiocephalic vein, having previously received the lymphatics from the thorax and the left side of the head and left anterior extremity. Those from the right side of the head and right anterior limb usually enter by a small distinct trunk into the corresponding part of the right brachiocephalic vein. The duct, and also the principal lymphatic vessels, are provided with valves.

Lymphatic glands, rarely met with in the Sauropsida, are usually present in mammals, both in the general and in the lacteal system, the latter being called “mesenteric glands.” They are round or oval masses, situated upon the course of the vessels, which break up in them and assume a plexiform arrangement, and then reunite as they emerge. No structures corresponding to the pulsating “lymphatic hearts” of the lower vertebrates have been met with in mammals.

Associated with the vascular and lymphatic systems are certain bodies, the functions of which are not properly understood, and which are usually, on account of their general appearanee, grouped together under the name of “ductless glands.” Of these the “spleen” is the largest, and single, always placed in mammals in relation to the fundus or left end of the stomach, to which it is attached by a fold of peritoneum. It is dark-coloured and spongy in substance, and has a depression on one side or “hilus,” into which the splenic artery, a branch of the cceliac axis of the abdominal aorta, enters, and from which the vein, which joins the portal system, emerges. It varies much in size and form in different mammals, being relatively very small’in the Cetacea. It is sometimes almost spherical, but more often flattened, oval, triangular, or elongated, and occasionally, as in Monotremes and most Marsupials, triradiate. The “suprarenal bodies” or “adrenals” are two in number, each situated either in contact with or at a short distance in front of the anterior extremity of the kidney. They are abundantly supplied with nerves, and are much larger relatively in early than in adult life. The “thyroid body,” or rather bodies, for there are generally two, though in Man and some other species connected by an isthmus passing across the middle line, are constant in mammals, though only met with in a rudimentary condition, if at all, in other vertebrates. They are situated in the neck, in contact with the sides of the anterior extremity of the trachea. The “thymus lies in the anterior part of the thorax, between the sternum and the great vessels al the base of the heart, and differs from the thyroid in being median and single, and having a central cavity. It attains its greatest development during the period of lactation, and then diminishes and generally disappears before full growth is attained.

Respiratory Organs.— Mammals breathe occasionally through the mouth, but usually, and in many cases exclusively, through the nostrils or nares. These are apertures, always paired (except in the toothed Cetacea, where they unite to form a single external opening), and situated at the fore part of the face, generally at or beneath the end of the muzzle, a median prominence above the mouth. This is sometimes elongated to form a proboscis, to the extremity of which the nostrils are carried, and which attains its maximum of development in the Elephant. In the Cetacea the nostrils are situated at a considerable distance behind the anterior end of the face, upon the highest part of the head, and are called “blow-holes,” from the peculiar mode of respiration of these animals. The nostrils are kept open by means of cartilages which surround their aperture, and which many animals have the power of moving so as to cause partial dilatation or contraction. In diving animals, as Seals and Cetacea, they can be completely closed at will so as to prevent the entrance of water when beneath the surface. The passage to which the nostrils lead is in most mammals filled by a more or less complex sieve-like apparatus, formed of the convoluted turbinal bones and cartilages, over which a moist, vascular, ciliated mucous membrane is spread, and which intercepts particles of dust, and also aids in warming the inspired air before it reaches the lungs. In the Proboscidea, in which these functions are performed by the walls of the long tubular proboscis, this apparatus is entirely wanting. The narial passages have the organ of smell situated in their upper part, and communicate posteriorly with the pharynx, and through the glottis with the “trachea” or windpipe, a tube by which the air is conveyed to and from the lungs. The permanent patency of the trachea during the varied movements of the neck is provided for by its walls being stiffened by a series of cartilaginous rings or hoops, which in most mammals are incomplete behind. Having entered the thorax, the trachea bifurcates into the two bronchi, one of which enters, and, dividing dichotomously, ramifies through, each lung. In some of the Cetacea and Artiodactyla a third bronchus is given off from the lower part of the trachea, above its bifurcation, and enters the right lung.

The upper end of the trachea is modified into the organ of voice or “larynx,” the air passing through which to and from the lungs is made use of to set the edges of the “vocal cords,” fibrous bands stretched one on each side of the tube, into vibration. The larynx is composed of several cartilages, of which the “thyroid,” the “cricoid,” and the “arytenoid” are the principal, moved upon one another by muscles, and suspended from the hyoidean arch. By alteration of the relative position of these cartilages the cords can be tightened or relaxed, approximated or divaricated, as required to modulate the tone and volume of the voice. A median tongue-shaped fibro-cartilage at the top of the larynx, the “epiglottis,” protects the “glottis,” or aperture by which the larynx communicates with the pharynx, from the entry of particles of food during deglutition. The form of the larynx and development of the vocal cords present many variations in different members of the class, the greatest modification from the ordinary type being met with in the Cetacea, where the arytenoid cartilages and epiglottis are united in a tubular manner, project into the nasal passage, and, being grasped by the muscular posterior margin of the palate, provide a direct channel of communication from the lungs to the external surface. An approach to this condition is met with in the Hippopotamus and some other Ungulates. Nearly all mammals have a voice, although sometimes it is only exercised at seasons of sexual excitement. Some Marsupials and Edentates appear to be quite mute. In no mammal is there an inferior larynx, or “syrinx, as in birds.

The thoracic cavity of mammals differs from that of the Sauropsida in being completely separated from the abdomen by a muscular partition, the “diaphragm,” attached to the vertebral column, the ribs, and the sternum. This is much arched, with the convexity towards the thorax, so that when its fibres contract it is flattened and the cavity of the thorax increased, and when they are relaxed the cavityisdiminished. The lungs are suspended freely in the thorax, one on each side of the heart, being attached only by the root, which consists of the bronchus or air-tube, and pulmonary arteries and veins by which the blood is passed backwards and forwards between the heart and the lungs. The remaining part of the surface of each lung is covered by serous membrane, the “pleura,” and, whatever the state of distension or contraction of the chest-wall, is accurately in contact with it. Inspiration is effected by the contraction of the diaphragm, and by the intercostal and other muscles elevating or bringing forward the ribs, and thus throwing the sternum farther away from the vertebral column. As the surface of the lung must follow the chest-wall, the organ is itself expanded, and air rushes in through the trachea to fill all the minute cells in which the ultimate ramifications of the bronchi terminate. In ordinary expiration very little muscular power is expended, the elasticity of the lungs and surrounding parts being sufficient to cause a state of contraction and to drive out at least a portion of the air contained in the cells, when the muscular stimulus is withdrawn. The lungs are sometimes simple externally, as in the Sirenia (where they are greatly elongated) and the Cetacea, but they are more often divided by deep fissures into one or more lobes. The right lung is usually larger and more subdivided than the left. It often has a small distinct lobe behind, wanting on the left side, and hence called lobulus azygos.

Most mammals have in connexion with the air passages certain diverticuli or pouches containing air, the use of which is not always easy to divine. The numerous air sinuses situated between the outer and inner tables of the bones of the head, which in Man are represented by the antrum of Highmore and the frontal and sphenoidal sinuses, and which attain their maximum of development in the Indian Elephant, are obviously for the mechanical purpose of allowing expansion of the bone surface without increase of weight. They are connected with the nasal passages. The Eustachian tubes pass from the back of the pharynx into the cavity of the tympanum, into which and the mastoid cells they allow air to pass. In the Equidae there are large post-pharyngeal air sacs in connexion with them. The Dolphins have an exceedingly complicated system of air sacs in connexion with the nasal passages just within the nostrils, and the Tapir and Horses have blind sacs in the same situation. In the males of some Seals {Cystophora and Macrorhinus y ) large pouches, which the animal can inflate with air, but which at other times are flaccid, and which are not developed in the young animal or the female, arise from the upper part of the nasal passages, and lie immediately under the skin of the face. These are very analogous, although not in the same situation, to the gular pouch of the male Bustard. The larynx has frequently membranous pouches in connexion with it, into which air passes. These may be lateral and opening just above the vocal cords, constituting the sacculi laryngis, found in a rudimentary state in Man, and attaining an enormous development, reaching to the shoulders and axillae, in some of the Anthropoid Apes; or they may be median, opening in front either above or below the thyroid and cricoid cartilages, as in the Howling and other Monkeys, and also in the Whalebone Whales and Great Anteater.

Urinary Organs.— The kidneys of mammals are more compact and definite in form than in other vertebrates, being usually more or less oval, with an indent on the side turned towards the middle line from and into which the vessels and ducts pass. They are distinctly divided into a cortical secretory portion, composed mainly of convoluted tubes, and containing Malpighian bodies, and a medullary excreting portion, formed of straight tubes converging towards a papilla, embraced by the commencement of the ureter or duct of the organ. The kidneys of some mammals, as most Monkeys, Carnivores, Rodents, &c., are simple, with a single papilla into which all the renal tubuli enter. In others, as Man, there are many pyramids of the medullary portion, each with its papilla, opening into a division (calyx) of the upper end of the ureter. Such kidneys are, either in the embryonic condition only or throughout life, lobulated on the surface. In some cases, as in Bears, Seals, and especially the Cetacea, the lobulation is carried further, the whole organ being composed of a mass of renules, loosely united by connective tissue, and with separate ducts, which soon join to form the common ureter. In all mammals except the Monotremes the ureters terminate by slit-like valvular openings in the urinary bladder. This receptacle when filled discharges its contents through the single median urethra, which in the male is almost invariably included in the penis, and in the females of some species of Rodents, Insectivores, and Lemurs has a similar relation to the clitoris. In the Monotremes, though the bladder is present, the ureters do not enter into it, but into the urogenital canal some distance below it, the orifice of the genital duct intervening.

Nervous System and Organs of Sense.

The brain of mammals shows a higher condition of organization than that of other vertebrates. The cerebral hemispheres have a greater preponderance compared to other parts, especially to the so-called optic lobes, or corpora quadrigemina, which are completely concealed by them. The commissural system of the hemispheres is much more complete, both fornix and corpus callosum being present in some form; and, when the latter is rudimentary, as in Marsupials and Monotremes, its deficiency is made up for by the great size of the anterior commissure. The lateral lobes of the cerebellum, wanting in lower vertebrates, are well developed and connected by a transverse commissure, the pons Varolii. The whole brain, owing especially to the size of the cerebral hemispheres, is considerably larger relatively to the bulk of the animal than in other classes, but it must be recollected that the size of its brain depends upon many circumstances besides the degree of intelligence which an animal possesses, although this is certainly one. Man’s brain is many times larger than that of all other known mammals of equal bulk, and even three times as large as that of the most nearly allied Ape. Equal bulk of body is here mentioned, because, in drawing any conclusions from the size of the brain compared with that of the entire animal, it is always necessary to take into consideration the fact that in every natural group of closely allied animals the larger species have much smaller brains relatively to their general size than the smaller species, so that, in making any effective comparison among animals belonging to different groups, species of the same size must be selected. It may be true that the brain of a Mouse is, as compared with the size of its body, larger than that of a Man, but, if it were possible to reduce an animal having the general organization of a Man to the size of a Mouse, its brain would doubtless be very many times larger; and conversely, as shown by the rapid diminution of the relative size of the brain in all the large members of the Rodent order, a Mouse magnified to the size of a Man would, if the general rule were observed, have a brain exceedingly inferior in volume. Although the brain of the large species of Whales is, as commonly stated, the smallest in proportion to the bulk of the animal of any mammal, this does not invalidate the general proposition that the Cetacea have very large brains compared with terrestrial mammals, as the Ungulata, or even the aquatic Sirenia, as may be proved by placing the brain of a Dolphin by the side of that of a Sheep or Pig, or a Manatee of equal general weight. It is only because the universally observed difference between the slower ratio of increase of the brain compared with that of the body becomes so enormous in these immense creatures that they are accredited with small brains.

The presence or absence of “sulci” or fissures on the surface of the hemisphere, dividing it into “convolutions” or “gyri,” and increasing the superficies of the cortical grey matter, as well as allowing the pia mater with its nutrient blood-vessels to penetrate into the cerebral substance, follow somewhat similar rules. They are related partly to the high or low condition of organization of the species, but also in a great degree to the size of the cerebral hemispheres. In very small species of all groups, even the Primates, they are absent, and in the largest species of groups so low in the scale as the Marsupials and Edentates they are found. They reach their maximum of development in the Cetacea·.

The researches of palaeontologists, founded upon studies of casts of the interior of the cranial cavity of extinct forms, have shown that, in many natural groups of mammals, if not in all, the brain has increased in size, and also in complexity of surface foldings, with the advance of time,—indicating in this, as in so many other respects, a gradual progress from a lower to a higher type of development.

The twelve pairs of cranial nerves generally recognized in veftebrates are all usually found in mammals, though the olfactory nerves are excessively rudimentary, if not altogether absent, in the Toothed Whales. The spinal cord, or continuation of the central nervous axis, lies in the canal formed by the neural arches of the vertebrae, and gives off the compound double-rooted nerves of the trunk and the extremities corresponding in number to the vertebrae, through the interspaces between which they pass out to their destination. The cord is somewhat enlarged at the two points where it gives off the great nerves to the anterior andthe posterior extremities, which from their interlacements soon after their origin are called respectively the brachial and lumbar plexuses. The ganglionic or sympathetic portion of the nervous system is well developed, and presents few modifications.

The sense of touch is situated in the skin generally, but is most acute in certain regions more or less specialized for the purpose by the presence of tactile papillae, such as portions of the face, especially the lips and end of the snout, and the extremities of the limbs when these are used for other purposes than mere progression, and the under surface of the end of the tail in some Monkeys. The “vibrissae” or long stiff bristles situated on the face of many mammals are rendered extremely sensitive to touch by the abundant supply of branches from the fifth nerve to their basal papillae. In Bats, the extended wing membranes, and probably also the large ears and the folds and prominences of skin about the face of some species, are so sensitive as to receive impressions even from the different degrees of resistance of the air, and so enable the animals to avoid coming in contact with obstacles to their nocturnal flight.

The organs of the other special senses are confined to the head. Taste is situated in the papillae scattered on the dorsal surface of the tongue. The organ of smell is present in all mammals except the Toothed Whales. It consists of a ramification of the olfactory nerves over a plicated, moist, mucous membrane, supported by folded plates of bone, placed on each side of the septum nasi in the roof, or often in a partially distinct upper chamber of the nasal passage, so arranged that, of the air passing into the lungs in inspiration, some comes in contact with it, causing the perception of any odorous particles with which it may be charged. Many mammals possess intense powers of smelling certain odours which others are quite unable to appreciate, and the influence which this sense exercises over the wellbeing of many species is very great, especially in indicating the proximity of others of the same kind, and giving warning of the approach of enemies. The development and modification of the sense of smell is probably associated with that of the odorous secretion of the cutaneous glands.

The organ of sight is quite rudimentary, and even concealed beneath the integument, in some burrowing Rodents and Insectivores, and is most imperfectly developed in the Platanista, or Freshwater Dolphin of the rivers of India. In all other mammals the · eyeball has the structure characteristic of the organ in the higher Vertebrata, consisting of parts through which the rays of light are admitted, regulated, and concentrated upon the sensitive expansion of the optic nerve lining the posterior part of the ball. A portion of the fibro-vascular and highly pigmented layer, the choroid, which is interposed between the retina and the outer sclerotic coat, is in many mammals modified into a brilliantly coloured light-reflecting surface, the tapetum lucidum. There is never a pecten or marsupium, as in the Sauropsida, nor is the sclerotic ever supported by a ring of flattened ossicles, as is so frequently the case in the lower vertebrated classes. The eyeball is moved in various directions by a series of muscles—the four recti, two obliqui, and, except in the higher Primates, a posterior retractor muscle called choanoid. It is protected by the lids, generally distinctly separated into an upper and a lower-movable flap, which, when closed, meet over the front of the eye in a more or less horizontal line; but sometimes, as in the Sirenia, the lids are not distinct, and the aperture is circular, closing to a point. In almost all mammals below the Primates, except the Cetacea, a u nictitating membrane” or third eyelid is placed at the inner corner of the eyeball, and works horizontally across the front of the ball within the true lids. Its action is instantaneous, being apparently for the purpose of cleaning the front of the transparent cornea, a function which is unnecessary in animals whose eyes are habitually bathed in water, and which in Man and his nearest allies is performed by winking the true eyelids. Except in Cetacea the surface is kept moist by the secretion of the lacrymal gland, placed under the upper lid at its outer side, and the lids are lubricated by the Harderian and Meibomian glands, the former being situated at the inner side of the orbit, and especially related to the nictitating membrane, the latter in the lining membrane of the lids.

The organ of hearing is enclosed in a bony capsule (periotic) situated in the side of the head, intercalated between the posterior (occipital) and the penultimate (parietal) segment of the skull. It has, in common with other vertebrates, three semicircular canals and a vestibule, but the cochlea is more fully developed than in Sauropsida, and, except in the Monotremes, spirally convoluted. The tympanic cavity is often dilated below, forming a smooth rounded prominence on the base of the skull, the tympanic bulla. The three principal ossicles, the “malleus,” “incus,” and “stapes,” are always present, but variable in characters. In the Sirenia, Cetacea, and Seals they are massivem form, being in the first-named order of larger size than in any other mammals. In the Cetacea the malleus is ankylosed to the tympanic; in other mammals it is connected only with the membrana tympani. The stapes in the lower orders —Edentates, Marsupials, and Monotremes—has a great tendency to assume the columnar form of the corresponding bone in Sauropsida, its two rami entirely or partially coalescing. The tympanic membrane (drum of the ear) forms the outer wall of the cavity. In the foetal state it is level with the external surface of the skull, and remains so permanently in a few mammals, as the American Monkeys; but commonly, by the growth of the squamosal bone, it becomes deeply buried at the bottom of a bony tube (meatus auditorius externus), which is continued to the surface of the skin in a fibrous or fibro-cartilaginous form. In Whales, owing to the thickness of the subcutaneous adipose tissue, this is of great length, and is also extremely narrow. In most aquatic and burrowing animals the meatus opens upon the surface by a simple aperture, but in the large majority of the class there is a projecting fold of skin, strengthened by fibro-cartilages, called the pinna or auricle, or “external ear,” of very variable size and shape, generally movably articulated on the skull, and provided with muscles to vary its position, as it helps to collect and direct the vibrations of sound into the meatus.

Reproductive Organs.

In the male the testes retain nearly their primitive or internal position throughout life in the Monotremata, Sirenia, Cetacea, most Edentata, Hyracoidea, Proboscidea, and Seals, but in other orders they either periodically (as in Rodentia, Insectivora, and Chiroptera) or permanently pass out of the abdominal cavity through the inguinal canal, forming a projection beneath the skin of the perineum, or becoming suspended in a distinct pouch of the integument called scrotum. All the Marsupials have a pedunculated scrotum, the position of which differs from that of other mammals, being in front of, instead of behind, the preputial orifice. The presence, absence, or comparative size and number of the accessory generative glands—prostate, vesicular, and Cowper’s glands, as they are called—vary much in different groups of mammals. The penis is almost always completely developed, consisting of two corpora cavernosa attached to the ischial bones, and of a median corpus spongiosum enclosing the urethra, and forming the glans at the distal portion of the organ. In Marsupials, Monotremes, and the Sloths and Anteaters, the corpora cavernosa are not attached directly to the ischia, and in the last-named the penis is otherwise of a very rudimentary character, the corpus spongiosum not being present. In many Marsupials the glans penis is bifurcated. In most Primates, Carnivora, Rodentia, Insectivora, and Chiroptera, but in no other orders, an os penis is present.

In the female, the ovaries retain permanently their original abdominal position, or only descend a short distance into the pelvis. They are of comparatively smaller size than in other vertebrates, and have a definite flattened oval form, and are enclosed in a more or less firm “tunica albugenia.” The oviduct has a trumpet-like, and usually fimbriated abdominal aperture, and is more or less differentiated into three portions :—(1) a contracted upper part, called in Man and the higher mammals “Fallopian tube”; (2) an expanded part with muscular walls, in which the ovum undergoes the changes by which it is developed into the foetus, called the “uterus”; (3) a canal, the “vagina,” separated from the last by a valvular aperture, and terminating in the urino-genital canal, or common urinal and genital passage, which in higher mammals is so short as scarcely to be distinct from the last. The complete distinction of the oviducts of the two sides throughout their whole length, found in all lower vertebrates, only occurs in this class in Monotremes, a prevailing mammalian characteristic being their more or less perfect coalescence in the middle line to form a single median canal. In the Marsupials this union only includes the lower part of the vagina; in most Placentalia it extends to the whole vagina and a certain portion of the uterus, which cavity is then described as “bicornuate.” In the higher mammals, as in Man, and also in some of the Edentates, the whole of the uterus is single, the contracted upper portion of the oviducts or Fallopian tubes, as they are then called, entering its upper lateral angles by small apertures. In certain lower forms of mammals the urino-genital canal opens with the termination of the rectum into a common cloaca, as in other vertebrates; but it is characteristic of the majority of the class that the two orifices are more or less distinct externally.

Mammary glands, which secrete the milk by which the young are nourished during the first portion of their existence after birth, are present in both sexes in all mammals, though usually only functional in the female. In the Monotremes alone, their orifices are mere scattered pores in the skin, but in all others they are situated upon the end of conical elevations, called mammillae or teats, which, taken into the mouth of the young animal, facilitate the process of sucking. These are always placed in pairs upon some part of the ventral surface of the body, but varying greatly in number and position in different groups. In the Cetacea, where the prolonged action of sucking would be incompatible with their subaqueous life, the ducts of the glands are dilated into large reservoirs from which the contents are injected into the mouth of the young animal by the action of a compressor muscle.

Secondary sexual characters, or modifications of structure peculiar to one sex, but not directly related to the reproductive function, are very general in mammals. They almost always consist of the acquisition or perfection of some character by the male as it attains maturity, which is not found in the female or the young in either sex. In a large number of cases these clearly relate to the combats in which the males of many species engage for the possession of the females during the breeding season; others are apparently ornamental, and of many it is still difficult to apprehend the meaning. Many suggestions on this subject will, however, be found in the chapters devoted to it in Darwin’s work on The Descent of Man and Selection in Relation to Sex, where most of the best-known instances are collected. Superiority of size and strength in the male of many species is a well-marked secondary sexual character related to the purpose indicated above, being probably perpetuated by the survivors or victors in combats transmitting to their descendants those qualities which gave them advantages over others of their kind. To the same category belong the great development of the canine teeth of the males of many species which do not use these organs in procuring their food, as the Apes, Swine, Musk and some other Deer, the tusk of the male Narwhal, the antlers of Deer, which are present in most cases only in the males, and the usual superiority in size and strength of the horns of the Bovidae. Other secondary sexual characters, the use of which is not so obvious, or which may only relate to ornament, are the presence of masses or tufts of long hair on different parts of the body, as the mane of the male Lion and Bison, the beards of some Ruminants and Bats (as Taphozous melanopogon), Monkeys, and of Man, and all the variations of coloration in the sexes, in which, as a general rule, the adult male is darker and more vividly coloured than the female. Here may also be mentioned the presence or the greater development of odoriferous glands in the male, as in the Musk Deer, and the remarkable perforated spur with its gland and duct, so like the poison-tooth of the venomous serpents, found in the males of both Ornithorhynchus and Echidna, the use of which is at present unknown.

Placenta.— The development of the mammalian ovum, and the changes which the various tissues and organs of the body undergo in the process of growth, are too intricate subjects to be explained without entering into details incompatible with the limits of this article, especially as they scarcely differ, excepting in their later stages, from those of other vertebrates, upon which, owing to the greater facilities these present for examination and study, the subject has been more fully worked out. There are, however, some points which require notice, as peculiar to the mammalian class, and as affording at least some hints upon the difficult subject of the affinities and classification of the members of the group.

The nourishment of the foetus during intra-uterine life takes place through the medium of certain structures, partly belonging to the foetus itself and partly belonging to the inner parietes of the uterus of the parent. These in their complete form constitute the complex organ called the “placenta,” which serves as the medium of communication between the mother and foetus, and in which the physiological processes that are concerned in the nutrition of the latter take place; but, as we shall see, though a placenta, in the usual acceptation of the term, is peculiar to the mammalian class, it is not in all of its members that one is developed. The structures to which we shall have especially to refer are the outer tunic of the ovum, to which, however formed, the term “chorion” is commonly applied, and two sac-like organs connected with the body cavity of the embryo, both formed from the splanchnic mesoblast, lined by a layer of the hypoblast. These are the “umbilical vesicle” or “yolk sac” and the “allantois.”

The umbilical vesicle is a thin membrane enclosing the yolk, which by the doubling in of the ventral walls of the embryo becomes gradually formed into a distinct sac external to the body, with a pedicle'(the omphalo-enteric duct) by which for a time a communication is maintained between its cavity and the intestinal canal. In the walls of this sac blood-vessels (omphalo-meseraic or vitelline) are developed in connexion with the vascular system of the embryo, through which, either by their contact with the outer surface of the walls of the ovum, or by the absorption through them of the contents of the yolk sac, the nutrition of the embryo in the lower vertebrates chiefly takes place. In mammals the umbilical vesicle plays a comparatively subordinate part in the nourishment of the foetus, its function being generally superseded by the allantois.

The last-named sac commences at a very early period as a diverticulum from the hinder end of the alimentary tract of the embryo. Its proximal portion afterwards becomes the urinary bladder, the contracted part between this and the cavity of the allantois proper constituting the urachus, which passes out of the body of the foetus at the umbilicus together with the vitelline duct. The mesoblastic tissue of the walls of the allantois soon becomes vascular; its arteries are supplied with foetal blood by the two hypogastric branches of the iliacs, or main divisions of the abdominal aorta, and the blood is returned by venous trunks which unite to form the single umbilical vein which runs to the under surface of the liver, where, part of it joining the portal vein and part entering the vena cava directly, it is brought to the heart. These are the vessels which, with their surrounding membranes, constitute the umbilical cord, the medium of communication between the foetus and the placenta, when that organ is fully developed.

The nature of the foetal membranes of the Monotremata is not known. In the Marsupialia the observations made many years ago by Professor Owen, upon the development of the Kangaroo, have recently been confirmed by Dr H. C. Chapman, but fuller investigations in different species and at different stages are still much to be desired. As far as is known, up to the period of the very premature birth of these animals the outer covering of the ovum or chorion is free from villi and not adherent to the uterine walls, for, though fitting into the folds of the latter, it is perfectly and readily separable in its entire extent from them. The umbilical vesicle is large, vascular, and adherent to a considerable portion of the chorion, while the allantois is relatively small, and, though the usual blood-vessels can be traced in it, it does not appear to contract any connexion with the chorion, and therefore much less with the walls of the uterus, of such a nature as to constitute a placenta. While in the uterus the nourishment of the foetus seems therefore to be derived from the umbilical vesicle, as in reptiles and birds, rather than from the uterine walls by means of the allantoic vessels, as in the higher mammals. The latter vessels, in fact, play even a much less important part in the development of these animals, not only than in the placental mammals, but even than in the Sauropsida, for they can scarcely have the respiratory function assigned to them in that group. Pulmonary respiration and the lacteal secretion of the mother very early supersede all other methods of providing the due supply both of oxygen and of food required for the development and growth of the young animal. In this sense the Marsupials may be looked upon as the most typically “mammalian” of the whole class. In no other group do the milk-secreting glands play such an important part in providing for the continuity of the race.

In the third primary division of the Mammalia, the so-called Placentalia, the umbilical vesicle generally does not quite unite with the chorion, and disappears as development proceeds, so that no trace of it can be seen in the membranes of an advanced embryo; but it may persist until the end of intra-uterine life as a distinct sac in the umbilical cord, or lying between the allantois and amnion. The disappearance or persistence of the umbilical vesicle does not. according to our present knowledge, appear to be correlated with a higher or lower general grade of development, as might be presupposed. It is stated to have been found in Man even up to the end of intra-uterine life, and also in the Carnivora, while in the Ungulata and Cetacea it disappears at an earlier age. In many, if not all, of the Rodentia, Insectivora, and Chiroptera, it plays a more important part, becoming adherent to a considerable part of the inner surface of the chorion, to which it conveys blood-vessels, although villi do not appear to be developed from the surface of this part, as they are on the portion of the chorion supplied by the allantoic vessels. These orders thus present to a certain extent a transitional condition from the Marsupials, although essentially different, in possessing the structures next to be described.

The special characteristic of the whole of the placental mammals constituting the majority of the class, is that the allantois and its vessels become intimately blended with a smaller or greater part of the parieties of the ovum, forming a structure on the outer surface of which villi are developed, and which, penetrating into corresponding cavities of the “decidua,” or soft, vascular, hypertrophied lining membrane of the uterus, constitutes the placenta. This organ may be regarded, as Professor Turner says, both in its function and in the relative arrangement of its constituent textures, as a specially modified secreting gland, the ducts of which are represented by the extremities of the blood-vessels of the foetal system. The passage of material from the maternal to the foetal system of vessels is not a simple percolation or diffusion through their walls, but is occasioned by the action of a layer of cells derived from the maternal or uterine structures, and interposed between the blood-vessels of the maternal part of the placenta and those of the villi covering the chorion, in which the embryonic vessels ramify.

The numerous modifications in the details of the structure of this organ relate to increasing the absorbing capacity of the vessels of the chorion, and are brought about either by increasing the complexity of the foetal villi and maternal crypts over a limited area, or by increasing the area of the part of the chorion covered by the placental villi, or by various combinations of the two methods.

The first class of variations has given rise to a distinction into two principal kinds of placenta—(1) simple or non-deciduate, and (2) deciduate. In the former the foetal villi are received into corresponding depressions of the maternal surface, from which at the period of parturition they are simply withdrawn. In the second or more complex form the relation is more intimate, a layer of greater or less thickness of the lining membrane of the uterus, called- “decidua,” becoming so intimately blended with the chorion as to form part of the placenta proper, or that structure which is cast off as a solid body at parturition. In other words, in the one case the line of separation between the placenta and uterus at birth takes place at the junction of the foetal and maternal structures, in the other through the latter, so that a portion of them, often of considerable thickness, and containing highly organized structures, is cast off with the former. It has been thought that the distinction between these two forms of placentation is so important as to constitute a sufficiently valid basis for a primary division of the placental mammals into two groups. It has, however, been shown that the distinction is one rather of degree than of kind, as intermediate conditions may exist, and it is not improbable that in different primary groups the simpler, non-deciduate form may have become developed independently into one or other of the more complex kinds.

Apart from its intimate structure, the placenta may be met with of very varied general form. It may consist of villi scattered more or less regularly over the greater part of the surface of the chorion, the two extremities or poles being usually more or less bare. This form is called the “diffused placenta.” It is probably a primitive condition, from which most of the others are derived, although its existence must presuppose the absence of the umbilical vesicle as a constituent of the chorionic wall. It is found at present in the Manis among Edentates, the Cetacea, Sirenia, the Perissodactyle Ungulates, and the Camels, Pigs, and Chevrotains among the Artiodactyles. Such placentae are always non-deciduate. In the true Ruminants or Pecora, among the Artiodactyle Ungulates, the villi are aggregated in masses called cotyledons, with bare spaces between. Such a placentation is called “polycotyledonary.” In another modification the villi are collected in a more or less broad band encircling the chorion, leaving a very large portion of the two poles bare, constituting the “zonary placenta,” characteristic of the Carnivora, and also occurring in the Elephant, Hyrax, and Orycteropus. The fact of the form of the placenta of these three last-named animals agreeing together, and with that of the Carnivora, does not, however, necessitate the ascription of zoological affinities, as the placenta jof the Carnivora has been shown to be at first discoidal, and to become zonary by spreading round the chorion in the course of development. In the other cases, although it must be admitted that the early stages have not been well observed, it is quite probable that it may be derived from a diffused placenta, in which the foetal villi have disappeared from a larger space than usual of the two poles of the ovum.

Iu another form one pole only of the chorion is non-vascular, the placenta assuming a dome or bell shape, as in the Lemurs and the Sloths. The transition from this, by the gradual restriction of the vascular area, is easy to the oval or discoidal form of placenta of the Anteaters, Armadillos, and Primates. The discoidal placenta of the Rodents, Insectivores, and Chiroptera, though showing so much superficial resemblance to that of the last-named order as to have caused them formerly to be associated in one primary group, is now known to be developed in another manner, not by the concentration of villi from a diffused to a limited area, but by retaining the area to which it was originally restricted in consequence of the large surface of chorion occupied, as before mentioned, by the umbilical vesicle. To compensate for the smallness of area, the complex or deciduate structure has been developed. We may conclude that, although the characters and arrangement of the foetal structures may not have that extreme importance which has been attributed to them by some zoologists, they will form, especially when more completely understood, valuable aids in the study of the natural affinities and evolution of the Mammalia.

CLASSIFICATION OF THE MAMMALIA.

As stated at the commencement of this article, the mammalian class, as at present known either by existing or extinct forms, is completely isolated from all other groups of the animal kingdom, but it is impossible to refrain from speculating as to its origin and nearest affinities. In arranging the classes of vertebrates in a linear series it is customary to place them in the following order— Pisces, Amphibia, Reptilia, Aves, Mammalia,— an order which may possibly indicate the relative degree of elevation to which the most completely developed members of each class attain, though it would be a great mistake to suppose that such an arrangement expresses the true relationship of one to the other, and still less must it be imagined that in the process of evolution any of the higher classes are necessarily derived directly from those nearest below them in this serial arrangement. On the contrary, some arguments recently set forth by Professor Huxley point very strongly to the conclusion that, in looking among vertebrates for the progenitors of the Mammalia, we must pass over all known forms of birds and reptiles, and go straight down to the Amphibia. In addition to the characters derived from the conformation of the pelvis upon which the argument is primarily based, the following reasons are given for this conclusion :—“The Amphibia are the only air-breathing Vertebrata which, like mammals, have a dicondylian skull. It is only in them that the articular element of the mandibular arch remains cartilaginous, while the quadrate ossification is small, and the squamosal extends down over it to the osseous elements of the mandible, thus affording an easy transition to the mammalian condition of those parts. The pectoral arch of the Monotremes is as much amphibian as it is sauropsidian; the carpus and the tarsus of all Sauropsida, except the Chelonia, are modified away from the Urodele type, while those of the mammal are directly reducible to it. Finally, the fact that in all Sauropsida it is a right aortic arch which is the main conduit of arterial blood leaving the heart, while in mammals it is a left aortic arch which performs this office, is a great stumbling-block in the way of the derivation of the Mammalia from any of the Sauropsida. But, if we suppose the earliest forms of both the Mammalia and the Sauropsida to have had a common Amphibian origin, there is no difficulty in the supposition that, from the first, it was a left aortic arch in the one series, and the corresponding right aortic arch in the other, which became the predominant feeder of the arterial system.”

There is so much in common between the very aberrant Monotremes, upon the structure of which the above conclusions are mainly based, and all other known mammals that we cannot but suppose they are derived, perhaps at some remote period, from one stock, some of the predominating characters of which survive in the existing Monotremes, though lost in most other members of the class. These “Prototheria,” as Professor Huxley terms them, have in their turn probably been derived from the same source as that in which the existing Amphibia on the one hand and the Sauropsida on the other have had their origin. The great divisions of the Vertebrata may be looked upon therefore as parallel, or rather diverging groups, each tending towards its own specialization, not in any way in the light of ancestor and descendant. No further advance of the Sauropsidian type, which has reached its highest perfection in the modern volant birds, would bring it nearer to the mammalian organization.

Restricting ourselves now to the class of mammals, as differentiated from other vertebrates, it will be unnecessary to repeat the oft-told history of the various attempts to express the prevailing knowledge of their structure and affinities in a systematic manner called a classification. The systems of Ray, Linnaeus, Cuvier, Owen, Milne-Edwards, Huxley, and others mark successive epochs of that knowledge. A perfect arrangement of any group of animals can only be obtained simultaneously with a perfect knowledge of their structure and life history, and from this, it need scarcely be said, we are still very far removed. If, as was formerly the case, classifications could be confined to existing species, the work would be far less difficult. By the extinction of intermediate forms the surviving groups have mostly come to be much isolated, and their limits can be readily determined and defined. The discovery of extinct species, which appears to be taking place at a constantly increasing rate, is by degrees breaking down these boundaries, and making definitions impossible, though at the same time it is throwing much light upon the affinities and probable origin of many groups now widely separated. A source of difficulty, and perhaps error, which this advancing knowledge has introduced, arises from the necessity of determining the position and relation of so many forms by the bones and teeth alone, without any hope of deriving aid from all those other structures of which we avail ourselves in the case of recent animals. These considerations will show that any classification advanced at present must be regarded as provisional. There are, however, some positions which seem to be so firmly established that it is very unlikely that we shall be dislodged from them by any further increase of knowledge, and which we should carefully distinguish from others which are acknowledged to be doubtful, and adopted rather for convenience, owing to the necessity of having some arrangement, than as representingunimpeachable truth.

One of the most certain and fundamental points in the classification of the Mammalia is, that all the animals now composing the class can be grouped primarily in three natural divisions, which, presenting very marked differentiating characters, and having no existing, or yet certainly demonstrated extinct, intermediate or transitional forms, may be considered as subclasses of equal value, taxonomically speaking, though very different in the numbers and importance of the animals at present composing them. These three groups are often called by the names originally proposed for them by De Blainville—(1) Or nithodelphia, (2) Didelphia, (3) Monodelphia,— the first being equivalent to the order Monotremata, the second to the Marsupialia, and the third including all the remaining members of the class. Although actual palaeontological proof is wanting, there is much reason to believe that each of these, as now existing, are survivors of distinct branches to which the earliest forms of mammals have successively given rise, and for which hypothetical branches Huxley has proposed the names of Prototheria, Metatheria, and Eutheria, names which, being far less open to objection than those of Blainville, we shall here use as equivalents for the latter.

The characters of the Prototheria can only be deduced from the two existing families, as hitherto no extinct animals which can be referred to other divisions of this remarkable and well-characterized group have been discovered. These two isolated forms, in many respects widely dissimilar, yet having numerous common characters which unite them together and distinguish them from the rest of the Mammalia, are the Omithorhynchidae and the Echidnidae, both restricted in their geographical range to the Australian region of the globe. Taken altogether they represent the lowest type of evolution of the mammalian class, and most of the characters in which they differ from the other two subclasses tend to connect them with the inferior vertebrates, the Sauropsida and Amphibia; for, though the name Ornithodelphia owes its origin to the resemblance of the structure of the female reproductive organs to those of birds, there is nothing especially bird-like about them.

Their principal distinctive characters are these. The brain has a very large anterior commissure, and a very small corpus callosum, agreeing exactly in this respect with the next group. The cerebral hemispheres, in Echidna at least, are well developed and convoluted on the surface. The auditory ossicles present a low grade of development, the malleus being very large, the incus small, and the stapes columelliform. They have no true teeth, though the jaws of Ornithorhynchus are provided with horny productions, which functionally supply their place. The coracoid bone is complete, and articulates with the sternum, and there is a large “interclavicle” or episternum in front of the sternum, and connecting it with the clavicles. There are also “epipubic” bones. The oviducts (not differentiated into uterine and Fallopian portions) are completely distinct, and open as in oviparous vertebrates separately into a cloacal chamber, and there is no distinct vagina. The testes of the male are abdominal in position throughout life, and the vasa deferentia open into the cloaca, not into a distinct urethral passage. The penis, attached to the ventral wall of the cloaca, is perforated by a canal in the greater part of its length, but not at the base, which is open as in reptiles and those birds which have such an organ, and brought only temporarily in contact with the termination of the vasa deferentia, so as to form a seminal urethra when required, but never transmits the urinary secretion. This condition is a distinct advance on that of the Sauropsida in the direction of the more complete development of these parts in most of the other Mammalia. The ureters do not open into the bladder, but behind it into the dorsal wall of the genito-urinary passage. The mammary glands have no distinct nipple, but pour out their secretion through numerous apertures in the skin. The early stages of the development of the young are not yet fully known, but they are produced in a very rudimentary condition, and appear never to be nourished by means of an allantoic placenta.

The Metatheria or Didelphia are represented at present by numerous species, presenting great diversities of general appearance, structure, and habits, although all united by many essential anatomical and physiological characters, which, taken altogether, give them an intermediate position between the Prototheria and the Eutheria. In the structure of the brain and the presence of epipubic bones they agree with the former, while in the structure of the ear bones and the shoulder girdle and the presence of teats on the mammary glands they resemble the latter, the reproductive organs belonging to neither one nor the other type, but presenting a special character representing an intermediate grade of development. The ureters open into the base of the bladder. The oviducts are differentiated into uterine and Fallopian portions, and open into a long and distinct vagina, quite separate from the cystic urethra. The penis is large, but its crura are not directly attached to the ischia. The spongy body has a large bifurcated bulb. The young are born in an exceedingly rudimentary condition, and are never nourished by means of an allantoic placenta, but are transferred to the nipple of the mother, to which they remain firmly attached for a considerable time, nourished by the milk injected into the mouth by compression of the muscle covering the mammary gland. They are therefore, as previously remarked (see p. 369), the most typically mammalian of the whole class. The nipples are nearly always concealed in a fold of the abdominal integument or “pouch” (marsupium) which serves to support and protect the young in their early helpless condition. The existing species of this group are entirely confined to the Australian region and the American continent, though in former times they had a more extended geographical range. The earliest mammals hitherto discovered appear (as far as the scanty evidence at present obtainable permits any such conclusion to be hazarded) to have belonged to this type, although it is reasonable to conclude that Prototheria (unless upon the improbable supposition that the existing forms have resulted from a process of degradation), and perhaps Eutheria, were their contemporaries far back in the Mesozoic age

The Eutheria, Monodelphia, or “placental mammals” (so called because the foetus is always nourished while within the uterus of the mother by means of an allantoic placenta) include at present by far the greater proportion of the class. While the survivors of the other groups have probably been for a long time in a stationary condition, these have, as there is already good evidence to show throughout all the Tertiary geological age, and by inference for some time before, been multiplying in numbers and variations of form, and attaining higher stages of development and specialization in various directions. They consequently exhibit far greater diversity of external or adaptive modification than is met with in either of the other subclasses,·— some being fitted to live as exclusively in the water as fishes, and others to emulate the aerial flight of birds.

To facilitate the study of the different component members of this large group, it is usual to separate them into certain divisions which are called “orders.” In the main zoologists are now of accord as to the general number and limits of these divisions among the existing forms, but the affinities and relationships of the orders to one another are far from being understood, and there are very many extinct forms already discovered which do not fit at all satisfactorily into any of the orders as commonly defined.

Commencing with the most easily-distinguished, we may first separate a group called Edentata, composed of several very distinct forms, the Sloths, Anteaters, and Armadillos, which under great modifications of characters of limbs and digestive organs, as well as habits of life, have just enough in common to make it probable that they are the very specialized survivors of an ancient group, most of the members of which are extinct, but which the researches of palaeontology have not yet revealed to us. The characters of their cerebral, dental, and in many cases of their reproductive organs show an inferior grade of organization to that of the generality of the subclass. The next order, about the limits of which there is no difficulty, is the Sirenia, aquatic vegetable-eating animals, with complete absence of hind limbs, and low cerebral organization,— represented in our present state of knowledge by but two existing genera, the Dugongs and Manatees, and by a few extinct forms, which, though approaching a more generalized mammalian type, show no special characters allying them to any of the other orders. Another equally well-marked and equally isolated, though far more numerously represented and diversified order, is that of the Cetacea, composed of the various forms of Whales, Dolphins, and Porpoises. In aquatic habits, external fish-like form, and absence of hind limbs they resemble the last, though in all other characters they are as widely removed as are any two orders among the Eutheria. The association by systematists of the Cetacea and Sirenia in one group can only be made either in ignorance of their true structure, or in an avowedly artificial system.

All the remaining orders are more nearly allied together, the steps by which they have become modified from one general type being in most cases not difficult to realize. Their dentition especially, however diversified in detail, always responds to the formula already described (see p. 353); and, although the existing forms are broken up into groups in most cases easy of definition, the discoveries already made in palaeontology have in great measure filled up the gaps between them.

Very isolated among existing Eutheria are the two species of Elephant constituting the order called Proboscidea. These, however, are now known to be the survivors of a large series of similar animals, Mammoths, Mastodons, and Dinothéria, which as we pass backwards in time gradually assume a more ordinary or generalized type; and the interval which was lately supposed to exist between even these and the rest of the class is partially bridged over by the discovery in American Eocene and early Miocene formations of the gigantic Dinocerata, evidently offshoots of the great group of hoofed animals, or Ungulata, represented in the actual fauna by the Horses, Rhinoceroses, Tapirs, Swine, and Ruminants. Almost as isolated as the Proboscidea among existing mammals are the few small species constituting the genus Hyrax, and in their case palaeontology affords no help at present, and therefore, pending further discoveries, it has been thought advisable in most recent systems to give them the honour of an order to themselves, under the name of Hyracoidea. But the number of extinct forms already known allied to the Ungulata, but not coming under the definition of either of the two groups {Artiodactyla and Perissodactyla') under which all existing species range themselves, is so great that either many new orders must be made for their reception or the definition of the old order Ungulata so far extended as to receive them all, in which case both Proboscidea and Hyracoidea might be included within it. Again the Rodentia, or gnawing animals—Rabbits, Rats, Squirrels, Porcupines, Beavers, &c.—are, if we look only at the present state of the class, most isolated. No one can doubt what is meant by a Rodent animal, or have any difficulty about defining it clearly, at least by its dental characters; yet our definitions break down before the extinct South American Mesotherium, half Rodent and half Ungulate, which leads by an easy transition to the still more truly Ungulate Toxodon, for the reception of which a distinct order (Toxodontia) has been proposed. The Insectivora and the Carnivora again are at present quite distinct orders, but they merge into one another through fossil forms, and are especially connected by the large group of primitive Carnivora, so abundantly represented in the Eocene deposits both of America and Europe, to which Cope has given the name of Creodonta. The transition from the Insectivores to the Lemurs is not great, and, strange to say, however different they now appear, the early forms of Lemurs are not easily distinguished from the primitive Ungulates. The Bats or Chiroptera are allied to the Insectivora in all characters but the extraordinary modification of their anterior extremities into wings, but this, like the want of the hind limbs in the Cetacea and Sirenia, makes such a clear distinction between them and all other mammals that, in the absence of any knowledge of intermediate or transitional forms, they can be perfectly separated, and form as well defined an order as any in the class. Lastly, we have the important and well-characterized group, called Primates, including all the Monkeys and Man, and the question is not yet solved as to how and through what forms it is linked on to the other groups. It is commonly assumed that the Lemurs are nothing more than inferior Primates, but the interval between them in the actual fauna of the world is very great, and our knowledge of numerous extinct species recently discovered in America, said to be intermediate in characters, is not yet sufficiently perfect to enable us to form a definite opinion upon the subject.

The distinctive characters of the generally recognized orders of mammals, with an account of their subdivisions and the principal forms contained in each, will be given further on.

GEOGRAPHICAL DISTRIBUTION OF MAMMALIA.

The existing species of few classes of the animal kingdom are better known than those of the Mammalia, and, owing to the comparatively limited methods of locomotion or transport which most of them possess, the area of distribution of each species is more definite and restricted than in some other classes. In the articles Birds and Distribution the various regions into which naturalists have divided the earth’s surface, according to the prevailing characters of its animal inhabitants, have been described, and in the latter the main facts connected with the distribution of mammals have been treated of. In the account of each group contained in the present article the particular circumstances relating to its geographical range will be mentioned. There is little therefore needed here, except a brief summary of the most important facts relating to this interesting subject.

As regards their distribution over the surface of the earth, mammals may be divided into three groups according to their principal methods of locomotion—(1) aerial, (2) aquatic, and (3) terrestrial.

1. Aerial Mammals.— This group only comprises the animals composing the single order Chiroptera, which differ from all other mammals in the fact that their principal means of transport from place to place is by aerial flight, as in the majority of birds and insects. Broad expanses of water, which form natural barriers to the spread of terrestrial mammals, are therefore no obstacles to their distribution; accordingly we find the general rule that mammals are not inhabitants of oceanic islands modified in their case. But even in this group, notwithstanding their exceptional powers of locomotion, different species, genera, and families inhabit very definite areas. Each zoological region of the earth has its characteristic Bats; and those of the New World and of the Old World are, with very few exceptions, quite distinct. This subject will be more fully treated of under the order Chiroptera. 2 . Aquatic Mammals.— Many mammals grouped for the present purpose as terrestrial pass a great portion of their lives in brooks, lakes, or rivers, and, being dependent upon such waters for obtaining their subsistence, are necessarily confined to their vicinity; but the truly aquatic mammals, or those living constantly in the water, and unable to move their quarters from place to place by land, are the orders Cetacea and Sirenia, with which may also be grouped the Seals, forming the Pinniped division of the order Carnivora.

For the marine Cetacea, animals mostly of large size and endowed with powers of rapid locomotion, there are obviously no barriers to universal distribution over the surface of the earth covered by sea, excent such as are interposed by uncongenial temperature or absence of suitable food. Nevertheless it was thought some years ago that the fact of a Whale or a Dolphin occurring in a sea distant from that in which it had usually been found was sufficient justification for considering it as a distinct species and imposing a new name upon it. There are now, however, so many cases known in which Cetaceans from the northern and southern seas, from the Atlantic and the Pacific Oceans, present absolutely no distinguishing external or anatomical characters upon which specific determination can be based that the opposite view is gaining ground; and, as some species are undoubtedly very widely distributed, almost cosmopolitan in fact, there seems little reason why many others should not be included in the same category. The evidence is satisfactory enough in those cases in which the intermediate regions are inhabited by the same forms, the cases of “continuous areas” of distribution. In those in which the areas of distribution are apparently discontinuous, there may be more room for doubt; but it must not be forgotten that the negative evidence is here of much less value than in the case of land animals, as the existence of Cetaceans in any particular part of the ocean is most'easily overlooked. The great Sperm Whale {Physeter macrocephalus) is known to be almost cosmopolitan, inhabiting or passing through all the tropical and temperate seas, although not found near either pole. At least three of the well-known species of Rorqual {Balaenoptera) of the British coasts are represented in the North Pacific, on the South American shores, and near New Zealand by species so closely allied that it is difficult to point out any valid distinctive characters, though it may perhaps be desirable to wait for a more complete examination of a large series of individuals before absolutely pronouncing them to be specifically identical. There is nothing yet known by which we can separate the“Humpback Whales” {Megaptera) of Greenland, the Cape of Good Hope, and Japan. The same may be said of the common Dolphin of the European seas {Delphinus delphis) and the so-called D. bairdii of the North Pacific and D. forsteri of the Australian seas. The Pilot Whale {Globicephalus mêlas) and the Pseudorca of the North Atlantic and of New Zealand are also precisely alike, as far as present knowledge enables us to judge. Many other similar cases might be given. Captain Maury collected much valuable evidence about the distribution of the larger Cetacea, and, finding Right Whales {Balstna) common in both northern and southern temperate seas, and absent in the intermediate region, laid down the axiom that “the torrid zone is to the Right Whale as a sea of fire, through which he cannot pass.” Hence all cetologists have assumed that the Right Whale of the North Atlantic {B. hiscay ensis), that of the South Seas {B. australis), and that of the North Pacific {B. japonica) are necessarily distinct species. The anatomical structure and external appearance of all are, however, as far as yet known, marvellously alike, and, unless some distinguishing characters can be pointed out, it seems scarcely justifiable to separate them upon geographical position alone; as, although the tropical seas may be usually avoided by them, it scarcely seems impossible, or even improbable, that some individuals of animals of such size and rapid powers of swimming may not have at some time traversed so small a space of ocean as that which divides the present habitual localities of these supposed distinct species. If identity or diversity of structural characters is not to be allowed as a test of species in these cases, as it is usually admitted to be in others, the study of their geographical distribution becomes an impossibility.

Although many species are thus apparently of such wide distribution, others are certainly restricted; thus the Arctic Right Whale (Balaena mysticetus) has been conclusively shown to be limited in its range to the region of the northern circumpolar ice, and no corresponding species has been met with in the southern hemisphere. In this case, not only temperature, but also the peculiarity of its mode υf feeding, may be the cause. The Narwhal and the Beluga have a very similar distribution, though the latter occasionally ranges farther south. The Hyperoodons are restricted to the North Atlantic, never entering, as far as is yet known, the tropical seas. Other species are exclusively tropical or austral in their range. One of the true Whalebone Whales (Neobalaena marginata) has only been met with hitherto in the seas round Australia and New Zealand, a large Ziphiυid (Berardius arnouxi) only near the last-named islands.

The Cetacea are not limited to the ocean, or even to salt water, some entering large rivers for considerable distances, and some being exclusively fluviatile. One species of Platanista is extensively distributed throughout nearly the whole of the river systems of the Ganges, Brahmaputra, and Indus, ascending as high as there is water enough to swim in, but apparently never passing out to sea. The individuals inhabiting the Indus and the Ganges must therefore have been for long ages isolated without developing any definite distinguishing anatomical characters, for those by which the supposed P. indi was formerly separated from P. gangetica have been shown by Anderson to be of no constant value. Orcella fluminalis appears to be limited to the Irawaddy river, and at least two distinct species of Dolphin, belonging to different genera, are found in the waters of the upper Amazon. It is remarkable, however, that none of the great lakes or inland seas of the world are, according to our present knowledge, inhabited by Cetaceans. A regular seasonal migration has been observed in many of the oceanic. Cetacea, especially those inhabiting the North Atlantic, but further observations upon this subject are still much needed.

The great difference in the manner of life of the Sirenia, as compared with that of the Cetacea, causes a corresponding difference in their geographical distribution. Slow in their movements, and feeding exclusively upon vegetable substances, water-grasses, or fuci, they are confined to rivers, estuaries, or coasts where these grow, and are not denizens of the open sea, although of course there is a possibility of accidental transport by the assistance of oceanic currents across considerable distances. Of the three genera existing within historic times, one (Manatus) is exclusively confined to the shores of the tropical Atlantic and the rivers entering into it, individuals scarcely specifically distinguishable being found both on the American and the African side of the ocean. The Dugong (Halicore) is distributed in different colonies, at present isolated, throughout the Indian Ocean from Arabia to North Australia. The llhytina or Northern Sea-Cow was, for some time before its extinction, limited to a single island in the extreme north of the Pacific Ocean.

The Pinnipeds, although capable of traversing long reaches of ocean, are less truly aquatic than the last two groups, always resorting to the land or to extensive icefloes for the purposes of breeding. The geographical range of each species is generally more or less restricted, usually according to climate, as they are mostly inhabitants either of the Arctic or Antarctic seas and adjacent temperate regions, very few being found within the tropics. For this reason the northern and the southern species are for the most part quite distinct. In fact, the only known exception is the case of a colony of the Sea-Elephant (Macrorhinus leoninus), the general range of which is in the southern hemisphere, inhabiting the coast of California. Even in this case a different specific name has been given to the northern form, but the characters by which it is distinguished are not of great importance, and probably, except for the abnormal geographical distribution, would never have been discovered. The most remarkable circumstance connected with the distribution of the Pinnipeds is the presence of members of the order in the three isolated great lakes or inland seas of Central Asia— the Caspian, Aral, and Baikal—which, notwithstanding their long isolation, have varied but slightly from species now inhabiting the Polar Seas.

3. Terrestrial Mammals.— One of the most important facts connected with the present distribution of terrestrial mammals, but one of which the cause is sufficiently obvious, is their entire absence, except where introduced by the direct agency of man, from all oceanic islands, including even the great New Zealand group. Another, equally striking, but less easily explained, is the very marked isolation as regards its mammalian fauna of the Australian region of zoologists. When once the narrow neutral ground on the border line between this and the Oriental region is passed, there is not found, notwithstanding the vast extent of land it comprises, a single indigenous placental or monodelphous mammal, except a few species of a single family (Muridae) of the very wide spread order Bodentia,— the Wild Dog or Dingo having been in all probability introduced. On the other hand, the members of the other two subclasses, the Prototheria or Ornitho~ delphia and the Metatlιeria or Didelphia, are almost entirely restricted to this region. It might have been said entirely, but for the presence of one family (Didelphidae) of the latter group in America.

The Eutheria or Monodelphia are distributed throughout the remaining geographical regions, as described in the article Distribution, and in many cases form valuable indications by which the natural boundaries of these divisions have been traced. Many anomalies, otherwise inexplicable in the present range of families and species, have been cleared up by the study of their distribution in former geological epochs, a subject in relation to which the present facts of distribution should always be studied. There are few lines of evidence so conclusive as this in favour of the existing species being modified lineal descendants of those which have lived in previous times upon the earth.

HISTORY OF THE MAMMALIA IN PAST TIMES.

As already intimated, such knowledge as we yet posses» of the history of mammals in past times is of very recent growth, and is still extremely incomplete. The very rapid advances which have been made in the last few years, especially in consequence of the explorations of rich fossiliferous beds in North America, have not only completely changed the present aspect of the science, but give such promise for the future that any sketch which we might now attempt of this branch of the subject could only be regarded as representing a transient phase of knowledge. It will be well, however, to gather together in this place the leading facts now ascertained with regard to the most ancient forms, as, owing to the uncertainty of their relationship with any of the existing orders, they will be most conveniently treated of separately, while the ascertained facts relating to the geological history of the forms more nearly allied to those now living will be more appropriately described under the account of the different groups into which the class may now be divided.

Mammals of the Mesozoic Period.

The hitherto discovered remains of mammals which existed anterior to the Tertiary period all belong to creatures of very small size, the largest scarcely exceeding the common Polecat or Squirrel. Some are known only by a few isolated teeth, others by nearly complete sets of these organs, and the majority by more or less perfect specimens of the rami of the lower jaw. It is a very curious circumstance that this part of the skeleton alone has been preserved in such a large number of instances. No complete cranium has ever been found, nor is there satisfactory evidence of the structure of the vertebral column or of the limbs of any single individual. The species already described from European strata amount to nearly thirty, which have been arranged in fifteen genera. Of these by far the greater number have been found at a single spot near Swanage in Dorsetshire, in a bed of calcareous mud only 40 feet long, 10 feet wide, and averaging 5 inches in depth. The marvellous results obtained by the exploration by Mr S. H. Beckles of this small fragment of the earth’s surface show by what accidents, as it were, our knowledge of the past history of life has been gained, and what may still remain in store where little thought of at present. A bed, apparently equally rich, has recently been discovered in the Territory of Wyoming, North America, the contents of which are being made known by Professor Marsh.

1. Mammals of the Triassic Period.— The Rhaetic formations, so named from the Rhaetian Alps of Bavaria, are the highest beds of the Trias, and are situated above the New Red Sandstone, and just below the Lias. In 1847 Professor Pleininger of Stuttgart, while assiduously sifting some sand from this formation, belonging to the Keuper of Diegerloch and Steinenbronn, discovered, among an immense mass of teeth, scales, and unrecognizable fragments of skeletons of fish and saurians, two minute teeth, each with well-defined, enamelled, tuberculated crowns and distinct roots, plainly showing their mammalian character. These, the oldest known evidence of the class, were considered by their discoverer to indicate a predaceous and carnivorous animal of very small size, to which he gave the name of Microlestes antiquus. Subsequently Mr C. Moore discovered in a bone bed of Rhaetic age filling a fissure in the mountain limestone at Holwell, near Frome in Somersetshire, various isolated teeth with their crowns much worn, but apparently including both upper and lower molars and a canine, which are assigned by Professor Owen to Pleininger’s genus Microlestes, and described specifically as Μ. moorei. Under the name of Hypsi-prymnopsis rhaeticus Prof. Boyd Dawkins has described a single tooth with two roots which he discovered in a Rhaetic marlstone at Watchet in Somersetshire, and which may be even somewhat older than the last. Professor Dawkins finds the nearest analogue of this tooth among recent mammals in the large trenchant premolar of the Rat-Kangaroo or Hypsiprymnus (see vol. xiii. p. 840, fig. 4), a resemblance not concurred in by Professor Owen, who refers it to the genus Microlestes. The minute size and worn condition of the tooth render it extremely difficult to form a decided opinion upon its characters, and therefore upon the affinities of the animal to which it belonged.

Still more satisfactory evidence of the presence of mammals at a period at least as ancient as the European Trias is afforded by the discovery of three nearly perfect mandibular rami in the Chatham coal-field of North Carolina by Dr Emmons, who, however, placed them as far back in age as the Permian, or altogether beyond the Mesozoic stage, a conclusion not now received. Of this animal, called Dromatherium sylvestre, the complete dentition of the lower jaw is known, and consists of three pointed incisors, separated by intervals, one canine, and ten molars, of which the first three have simple subcompressed crowns, and the remainder are multicuspid. The jaw figured by Dr Emmons is - r ⅞∙ of an inch in length. He considered it to belong to a placental Insectivore, but the number of molar teeth exceeds that of any existing member of that order, and is only found in some Marsupials. It was associated in the same bed with thecodont reptiles.

2. Mammals of the Jurassic Period.— In the ascending order of geological age the next remains of mammals have been met with in the Lower Oolite at Stonesfield in Oxfordshire, where they are associated with wing cases of insects, Plesiosaurs, Crocodiles, and Ptérodactyles. From this bed several specimens have been met with at various times, which have been placed in three genera.

A. Amphitherium, Blainville, 1838. The specimen (A. prevostii, see fig. 15) ppon which this genus was founded, was discovered in 1812, and examined in 1818 at Oxford by Cuvier, who pronounced it to be mammalian, and to resemble the jaw of an Opossum. This conclusion was afterwards disputed by De Blainville and others, who believed it to be reptilian, but the original determination is now generally accepted. Three rami of mandibles, all more or less perfect, are now known. The length of the jaw is rather less than an inch. It contains sixteen teeth, which, as defined by shape only, are— i 3, c 1, p 6, m 6, so that if the upper jaw had a corresponding number there would be sixty-four teeth in all,—a greater number than in any existing heterodont mammal, though equalled by some of the species from the Purbeck. Ιhe nearest approach to this number is in Myrmecdbius among recent Marsupials. The incisors are rather long and slender, the canines apparently not much larger than the incisors, all the premolars and molars two-routed—the former with a single large pointed cusp and small basal cusp on one or both sides, the latter quinquecuspidate. The lower margin of the angular process is slightly inflected, and the mylohyoid groove persistent, as in some of the existing Marsupials and in Whalebone Whales. This groove, a remnant of that which originally lodges Meckel’s cartilage, mistaken for a suture, was once considered evidence of the reptilian nature of these jaws. A second species is described as A. broderipii (Owen).

B. Phascolotherium, Owen, 1839. This is founded on a right ramus of the lower jaw, presenting the inner side to view. Its length is 1 , 4 inch. The number of teeth resemble those of existing insectivorous mammals, being i 3 or 4, c 1, p and nι 7, but not clearly defined from each other. One species, P. bucklandii (fig. 16).

C. Stereognathus, Charlesworth, 1854. S. ooliticus (fig. 17) is founded on a fragment of a jaw of minute size with three molar teeth in situ. The grinding surface is of quadrate form, of very little height, and supports six subequal cusps. Its affinities are quite problematical.

The freshwater bed previously alluded to, situated at Durdlestone Bay near Swanage, belongs to the Middle Purbeck series, intervening between the Middle Oolite and the Wealden. The first discovery of mammalian bones was made in this spot by Mr W. R. Brodie in 1854, but the subsequent explorations of Mr S. H. Beckles have yielded a surprising number of species. They are associated with numerous saurians, insects, and freshwater shells, as Paludina, Planorbis, and Cyclas. No less than eleven genera from this locality alone are fully described in Professor Owen’s memoir. These may be grouped as follows :—

A. With teeth arranged on the insectivorous type. Mandibular incisors more than two; canines well developed; premolars and molars cuspidate, seven or more :—(a) molars and premolars more than eight, mostly twelve (βpa-lacotherium, Amblothervum, Peralestes, Achyrodon, Pera-spalax, Peramus, Stylodon and Bolodon— the last known only by the maxillary teeth); (ό) molars and premolars seven or eight {Triconodon and Tria-canthodon). As any synopsis of the characters of these genera would be scarcely intelligible without minute descriptions and reference to figures, the reader who desires further information is referred to the memoir cited above.

B. With a single, strong, pointed, slightly curved incisor, placed close to the median line as in Rodents. No canine. Three or four compressed, trenchant, obliquely grooved premolars, increasing in size from first to last, and two small molars with low multituberculated crowns. Genus Plagiaulax, Falconer. This remarkable and highly specialized type has been the occasion of one of the most interesting discussions on the inferences which may be drawn as to the affinities and habits of an otherwise unknown animal from the structure of a small portion of its organization which occurs in the annals of natural history, a discussion carried on with great ability, ingenuity, and wealth of illustration on both sides. Dr Falconer maintained that it was more nearly allied to the Rat-Kangaroo [Hypsiprymnus} than to any other existing form, and that, as it is known that these animals feed upon grass and roots, “it may be inferred of Plagiaulax that the species were herbivorous or frugivorous. I can see nothing in the character of their teeth,” he adds, “to indicate that they were either insectivorous or omnivorous.” Professor Owen, on the other hand, from the same materials came to the conclusion that “the physiological deductions from the above-described characteristics of the lower jaw and teeth of Plagiaulax are that it was a carnivorous Marsupial.

It probably found its prey in the contemporary small insectivorous mammals and Lizards, supposing no herbivorous form like Stereognathus to have co-existed during the Upper Oolite period.” It is impossible here to give at any length the arguments by which these opposing views are respectively supported, but it may be indicated that the first-mentioned is strongly countenanced by the consideration of the following facts :— (1) all existing Marsupials may be divided, as far as their dentition is concerned, into two groups—(a) those which have a pair of large more or less procumbent incisors close to the symphysis of the lower jaw, and rudimentary or no canines (diprotodont dentition; families Phascolomyidae, Macropodidx i and Phalangistidae), and (δ) those which have numerous small incisors, and large pointed canines (polyprotodont dentition; families Peramelidae, Dasyuridae, and Didelphidae) ; (2) the vast majority of the former group are purely vegetable feeders, and almost all of the latter are carnivorous or insectivorous; and (3) Plagiaulax, so far as its structure is known, belongs obviously to the former group, and, as we have no sure basis for inferences as to the habits of an unknown animal but the knowledge of the habits of such as are known, we have no grounds for supposing that, its habits differed from those of its structural congeners.

That the two types of dentition still found among Marsupials should have existed side by side in so remote a period of time as that in which the Purbeck bone bed was deposited, and that one of these types should have already attained so singular a degree of specialization, is one of the most remarkable facts yet revealed by mammalian palaeontology. Whether the teeth of the upper jaw correspond also to the modern diprotodont type is a question of great interest, for the solution of which we must await future discoveries, of which we have more hope since the announcement by Professor Marsh of the existence, in considerable numbers, of small mammals in the American Jurassic formations of the Rocky Mountains, which conform in all their general characters to those of the English Purbecks, some being even considered to be generically identical. Both polyprotodont and diprotodont types are represented, the latter by a species called by its discoverer Ctenacodon serratus, very closely allied to Plagiaulax.

It will be of very great interest to know the mode of succession of the teeth of those early mammals, as it may throw some light upon the question of the relation of the succession of teeth in mammals generally with the same process in the inferior classes of the Vertebrata. There is, however, as yet very little, if any, reliable evidence upon the subject, but such as there is rather points to the fact of an absence or very feeble development of the diphyodont condition, resembling that of modern Marsupials. If this is so, it may lead to the somewhat startling conclusion that in the transition from the lower vertebrate to the mammal, by whatever process it took place, the indefinite reproduction of the teeth of the former was lost, and that a monophyodont condition supervened, which was again superseded by the peculiar definite diphyodont mode of succession characteristic of the most highly organized mammals.

There is nothing yet known in the structure of these small mammals of the Mesozoic ages of the world to connect them with the surviving representatives (the Monotremes) of the hypothetical Prototheria; but whether their position was among the Metatheria or Eutheria, or whether they represented generalized forms from which both these branches have been derived, it is impossible at present to say. To avoid the difficulty of endeavouring to find places for them in any of the existing groups, Marsh proposes to found two new orders for their reception— Pantotheria for those of the polyprotodont or insectivorous type of dentition, and Allotheria for Plagiaulax and its allies. The former may be convenient, but it is scarcely advisable to separate the latter ordinally, as long as we continue to place Phascolomys and Thylacinus, Chiromys and Lemur, Trichecus and Phoca in the same orders, for Plagiaulax and Amphitherium do not differ in the characters of their jaws and teeth more than any of these examples, which show how much the dentition may be modified with comparatively little general diversity of structure.

This scanty evidence of mammalian life must bear a very small proportion to that which doubtless existed during the greater part of the vast Mesozoic period. The Cretaceous formations have as yet yielded no trace of the presence of animals of this class; but the number and variety of species met with in the earliest Tertiary formations, when already differentiation into most of the existing leading divisions had taken place, strikingly proves the imperfect state of our geological record during the immediately antecedent ages of the world.

CHARACTERS OF THE DIFFERENT ORDERS AND FAMILIES AND OF THE PRINCIPAL FORMS OF THE MAMMALIA.

Subclass PROTOTHERIA or ORNITHODELPHIA.

The principal distinguishing characteristics of this group have been already given (p. 371). They apply not only to the subclass, but of course equally to the one order Monoteemata, in which the few known members of the group are commonly associated. In addition to the more important characters enumerated above, the following, which are common to all existing species, may be mentioned.

The dorso-thoracic vertebrae are nineteen in number, and have no terminal epiphyses to their bodies. The transverse processes of the cervical vertebrae are of autogenous formation, and remain suturally connected with the remainder of the vertebra until the animal is full-grown. Though in this respect they present an approximation to the Sauropsida (Reptiles and Birds), they differ from that group, inasmuch as there is not a gradual transition from these autogenous transverse processes of the neck (or cervical ribs, as they may be considered) into the thoracic ribs, for in the seventh vertebra the costal element is much smaller than in the other, indicative of a very marked separation of neck from thorax, not seen in the Sauropsida. The. upper ends of the ribs are attached to the sides of the bodies of the dorsal vertebrae only, and not to the transverse processes. The sternal ribs are well ossified, and there are distinct partly ossified intermediate ribs. The cerebral cavity, unlike that of the lower Marsupials or the Reptiles, with which they have so many structural affinities, is large and hemispherical, flattened below and arched above, and about as broad, as long. The cribriform plate of the ethmoid is nearly horizontal. The cranial walls are very thin, and smoothly rounded externally, and the sutures become completely obliterated in adult skulls, as in Birds. The broad occipital region slopes upwards and forwards, and the face is produced into a long and depressed rostrum. The bony palate is prolonged backwards, so that the posterior nares are nearly on a level with the glenoid fossa. The mandible is without distinct ascending ramus; the coronoid process and angle are rudimentary, and the two halves are loosely connected at the symphysis. The fibula has a broad, flattened process, projecting upwards from its upper extremity above the articulation, like an olecranon. In the male there is an additional, flat, curved ossicle on the hinder and tibial side of the plantar aspect of the tarsus, articulating chiefly to the tibia, which supports in the adult a sharp-pointed perforated horny spur, with which is connected the duct of a gland situated beneath the skin of the back of the thigh, the function of which is not yet clearly understood. (A rudimentary spur is found in the young female Omithorhynchus, but this disappears when the animal becomes adult.) The stomach is subglobular, simple; the alimentary canal has no ileo-caecal valve, or marked distinction between large and small intestine, but has a small, slender vermiform caecum with glandular walls. The liver is divided into the usual number of lobes characteristic of the Mammalia, and is provided with a gallbladder.

Although agreeing in so many important characters, the existing members of the group evidently represent two very diverging branches, perhaps as far removed as are the members of some of the accepted orders of the Eutheria. It would, however, be encumbering zoological science with new names to give them any other than the ordinarily known family designations of Ornithorhynchidae and Echidnidae. Family Ornitiiorπy.ncπidλ.

One genus, Omithorhynchus, Blumenbach, 1800. Cerebral hemispheres smooth. Premaxillae and mandible expanded anteriorly and supporting a horny beak something like that of a duck, bordered by a naked and very sensitive membranous expansion. The place of teeth supplied functionally by horny structures, elongated, narrow, and sharp-edged along the anterior part of the sides of the mouth, and broad, flat-topped or molariform behind. Legs short, fitted for swimming; feet webbed, each with five well-developed toes armed with large claws, and beyond which in the fore feet the interdigital membrane is extended. Vertebrae: C 7, D17, I. 2, 8 2, C 21. Acetabulum not perforated. Tongue not extensile. Mucous membrane of small intestine covered with delicate, close-set transverse folds or ridges. Tail rather short, broad, and depressed. Eyes very small. Fur close and soft. One species, 0. anatinus (Shaw), 0. paradoxus (Blum.), the duck-billed Platypus, or Water-Mole of the colonists, entirely aquatic in habits, diving with great facility, and burrowing in the banks of rivers. It feeds on water insects, small mollusca, and worms, and inhabits Australia and Tasmania. See Ornithorhynchus. Family Echidnidae.

Cerebral hemispheres larger and well convoluted. Facial portion of skull produced into a long, tapering, tubular rostrum, at the end of which the anterior nares are situated. Rami of mandible slender, styliform. Opening of mouth small, and placed below the extremity of the rostrum. No laterally placed horny teeth, though the palate and tongue are furnished with spines. Tongue very long, vermiform, slender, and protractile. Lining membrane of small intestine villous, but without transverse folds. Feet not webbed, but with long strong claws fitted for scratching and burrowing. The hinder feet with the ends of the toes turned outwards and backwards in the ordinary position of the animal when on the ground. Tail very short. Acetabulum with a large perforation, as in Birds. Calcaneal spur and gland of the male much smaller than in Ornithorhynchus. Fur intermixed with strong, sharp-pointed spines. Terrestrial and fossorial in habits, feeding exclusively on ants, and recalling in the structure of the mouth and various other parts relating to the peculiar mode of life the true Anteaters of the order Edentata.

Recent discoveries have shown that there are two distinct forms of this family, which may even be considered of generic value.

Echidna (Cuvier, 1797) or Tachyglossus (liliger, 1811). —Claws five on each foot. Rostrum moderately developed and straight. Vertebrae: C 7, D 16, I. 3, S 3, C 12. Tongue tapering at the tip, the spines restricted to the basal portion. The best-known species is E. aculeata (Shaw), found in Australia and Tasmania. The specimens from the latter locality, with longer fur almost concealing the spines, have been separated specifically under the name of E. setosa (Cuv. ).. Another species, E. lawesii (Ramsay), has lately been discovered in southern New Guinea. See Echidna. Acanthoglossus (Gervais).—Ungual phalanges and claws present only on the three middle digits of both fore and hind feet. Rostrum much elongated and curved downwards at the end. Vertebrae: C 7, D 17, I. 4, S 3, C 12. Tongue somewhat spoon-shaped near the tip, and armed on its dorsal surface with three rows of recurved spines. One species: A. bruijnii (Peters and Doria) (fig.22), from the mountainous regions of the northern part of New Guinea; considerably larger than E. aculeata. The external characters and osteology of this animal, one of the most interesting of recent zoological discoveries, have been fully described and figured by Gervais {Ostéographie des Monotrèmcs, Paris, 1878).

Among bones of extinct Marsupials of Pleistocene age from the Darling Downs, Mr Krefi't found a portion of a humerus of an Echidna, considerably larger than the existing Australian species, which he has named E. oweni. i Notwithstanding the strong presumption of antiquity of the Monotrematous type, derived from its inferiority of structure, no fossil remains of earlier date, referable to it, or connecting it with the lower vertebrates on the one hand and the higher mammals on the other, have yet been discovered.

Subclass METATHERIA or DIDELPHIA.

Although the great diversity in external form, in many anatomical characters, and in mode of life of various animals of this section might lead to their division into groups equivalent to the orders of the Eutheria, it is more convenient on the whole to adhere to the usual custom of treating them all as forming one order called Marsupialia, the limits of which are therefore equivalent to that of the subclass. The more essentially distinctive characters have been already pointed out (p. 371). These may be more fully stated as follows.

The brain is generally small in proportion to the size of the animal, and the surface folding of the cerebral hemispheres, though well marked in the larger species, is never very complex in character, and is absent in the smaller and medium-sized species. The arrangement of the folding of the inner wall of the cerebrum differs essentially from that of all known Eutheria, the hippocampal fissure being continued forward above the corpus callosum, which is of very small size. The anterior commissure is, on the other hand, greatly developed.

There are always true teeth, implanted in the usual manner in both jaws, and divisible, according to their position and form, into incisors, canines, premolars, and molars; but they vary much in number and character in the different families. Except in the genus Phascolomys, the number of incisors in the upper and lower jaws is never equal. The true molars are very generally four in number on each side of each jaw. The chief peculiarity in the dentition lies, however, in the mode of succession. There is no vertical displacement and succession of the teeth, except in the case of a single tooth on each side of each jaw, which is always the hindermost of the premolar series, and is preceded by a tooth having more or less of the characters of a true molar (see fig. 23), and is the only tooth comparable to those called “milk teeth” in the diphyodont Eutheria. In some cases (as in Hypsiprymnus) this tooth retains its place and function until the animal has nearly, if not quite, attained its full stature, and is not shed and replaced by its successor until after all the other teeth of the permanent series, including the posterior molars, are fully in place and use. In others, as the Thylacine, it is most rudimentary in form and size, being shed or absorbed before any of the other teeth have cut the gum, and therefore quite functionless. It must further be noted that there are some Marsupials, as the Wombat, Koala, Myrmecobius, and the Dasyures, in which no such milk tooth, even in a rudimentary state, has yet been discovered, possibly in some cases from want of materials for observation at the right stage of development.

Epipubic or marsupial bones are present in both sexes of nearly all species. In one genus alone, Thylacinus, they are not ossified. The number of dorso-lumbar vertebrae is always nineteen, although there are some apparent exceptions caused by the last lumbar being modified into a sacral vertebra. The number of pairs of ribs is nearly always thirteen. The tympanic bone remains permanently distinct. The carotid canal perforates the basi-sphenoid. The lacrymal foramen is situated upon or external to the anterior margin of the orbit, and there are generally large vacuities in the bony palate. The angle of the mandible is (except in Tarsipes) more or less inflected. The hyoid bones have always a peculiar form, consisting of a small, more or less lozenge-shaped basi-hyal, broad cerato-hyals, with the remainder of the anterior arch usually unossified, and stout, somewhat compressed thyro-hyals. There are two anterior venae cavae, into each of which a “vena azygos” enters. In the male the testes are always contained in a scrotum which is suspended by a narrow pedicle to the abdomen in front of the penis. The vasa deferentia open into a complete and continuous urethra, which is also the passage by which the urine escapes from the bladder, and is perfectly distinct from the passage for the faeces, although the anus and the termination of the urethro-sexual canal are embraced by the same sphincter muscle. The glans is often bifurcated anteriorly. In the female the oviducts never unite to form a common cavity or uterus, but open separately into the vagina, which at least for part of its course is double. During the very short period in which the embryo is contained in the uterus, its nourishment seems to be derived from the umbilical vesicle, the allantoic vessels not reaching the surface of the chorion to form a true placenta. The mammae vary much in number, but are always abdominal iu position, have long teats, and in most of the species are more or less enclosed in a fold of the integument forming a pouch or marsupium, though in some this is entirely wanting, and the newly-born, blind, naked, and helpless young, attached by their mouths to the teat, are merely concealed and protected by the hairy covering of the mother’s abdomen. In this stage of their existence they are fed by milk injected into their stomach by the contraction of the muscles covering the mammary gland, the respiratory organs being modified temporarily, much as they are permanently iu the Cetacea i — the elongated upper part of the larynx projecting into the posterior nares, and so maintaining a free communication between the lungs and the external surface independently of the mouth and gullet, thus averting the danger of suffocation while the milk is passing down the latter passage.

The existing species of Marsupials are, with the exception of one family (the Diddphidae), limited in geographical distribution to the Australian region, forming the chief mammalian fauna of Australia, New Guinea, and some of the adjacent islands. The Didelphidae are almost purely neotropical, one or two species ranging northwards into the Nearctic region. Fossil remains of members of this family have also been found in Europe in strata of the Eocene and early Miocene period.

In dividing the Marsupials into minor groups, it may be observed that one of the most obvious distinctive characters among them is derived from the form and arrangement of the teeth. In certain species, as the Opossums, Dasyures, and Tlιylacines, the incisors are numerous, small, and subequal in size and the canines large, as in the typical placental Carnivores (fig. 24 ; compare with that of Lion, vol. xiv. p. 680). To these the term “polyprotudont” is applied, and they are all more or less carnivorous in their habits. In others the central incisors are very prominent, and the lateral incisors and canines absent or subordinate in function (fig. 25). These are called “diprotodont,” and they are all wholly or in great part vegetable feeders.

In one group of these, the Wombats, there are but two incisors above and the same number below; but all the others, including the Kangaroos, Koalas, and Phalangen?, have two incisors below and as many as six above, three on each side, but of these the first or central pair is the most fully developed.·

Though this division is extremely convenient, a difficulty in accepting it as marking a radical separation of the order into two primary stocks is caused by the Peramelidae, which combine a polyprotodont form of dentition with a peculiar structure of the hind feet, so exactly resembling that of some of the best-marked di protodonts, as the Kangaroos, that it is difficult to believe that it can have been developed independently. Taking various combinations of characters into consideration, the existing Marsupials readily group themselyes into six very natural families, the characters of which can be thus defined :— [table]

B. All the teeth with persistent pulps. Incisors ⅜, large, scalpriform, with enamel on the outer surface only. No canines. Hind feet with four subequal outer toes; partially syndactylous and with rudimentary hallux. 6. Phascolomyidae. Family Didelphidm

Dentition: i∣, c⅛, p ⅜, m total 50. Incisors very small and pointed. Canines large. Premolars with compressed pointed crowns. Molars with numerous sharp cusps. The third premolar preceded by a deciduous multicuspidate molar, which remains in place until the animal is nearly adult. Limbs of moderate development, each with five complete and distinct toes, all of which are provided with short, compressed, curved, sharp claws of nearly equal size, except the first toe of the hind foot or hallux, which is large, widely separable from the others, to which it is opposed in climbing, and terminates in a dilated rounded extremity, without a nail. Tail generally long, partially naked and prehensile. Stomach simple. Caecum of small or moderate size. Pouch in some complete, in others represented by two lateral folds of the abdominal integument, partially covering the teats, while in some all trace of it is absent.. Vertebrae: C 7, D 13, I. 6, S 2, C 19-35.

The Didelphidae, or true Opossums, differ from all other Marsu-Çials in their habitat, being peculiar to the American continent, hey are mostly carnivorous or insectivorous in their diet, and arboreal in habits. One slightly aberrant form, with webbed hind feet, and aquatic mode of life, constitutes the genus Chironectes. The other numerous species are commonly included in the genus Didelphys. See Opossum. Family Dasyuridae.

Dentition: i ⅜, cf, p and m numerous, variable. Incisors small; canines well developed; molars with pointed cusps. Limbs equal. Fore feet with five subequal toes with claws. Hind feet with the four outer toes well-developed, and distinct from each other and bearing claws; the first (or hallux) clawless, generally rudimentary, sometimes entirely wanting. Stomach simple. No caecum. Predatory, carnivorous or insectivorous animals, inhabitants of Australia, Tasmania, and the southern parts of New Guinea and some of the adjacent islands. The aberrant genus Myrmecobius, though clearly a member of this family, is so sharply distinguished from all the others as to render a division into two subfamilies necessary.

Subfamily Dasyurinae.—This comprises the more typical Dasyuridae, in which the premolars and molars never exceed the normal number of seven on each side of each jaw, and in which the tongue is not specially extensile.

Thylacinus.— Dentition: i⅜, c∣, p ⅜, m ⅜ = 46. Incisors small, vertical, the outer one in the upper jaw larger than the others. Summit of the lower incisors, before they are worn, with a deep transverse groove, dividing it into an anterior and a posterior cusp. Canines long, strong, and conical. Premolars with compressed crowns, increasing in size from before backwards. True molars in general characters resembling those of Dasyurus, but of more simple form, the cusps being not so distinct nor sharply pointed. Milk molar very small, and shed before the animal leaves the mother’s pouch. General form very Dog-like. Head elongated. Muzzle pointed. Ears moderate, erect, triangular. Fur short and closely applied to the skin. Tail of moderate length, thick at the base and. tapering towards the apex, clothed with short hair. Hallux (including the metacarpal bone) wanting. Vertebrae: C 7, D 13, I. 6, 8 2, C 23. Marsupial bones represented only by small unossified fibro-cartilages.

The only known species of this genus, T. cynocephalus, though smaller than a common Wolf, is the largest predaceous Marsupial at present existing. It is now entirely confined to the island of Tasmania, although fragments of bones and teeth found in caves afford evidence that a closely allied species once inhabited the Australian mainland. The general colour of the Thylacine is greybrown, but it has a series of transverse black bands on the hinder part of the back and loins, whence the name of “Tiger” frequently applied to it by the colonists. It is also called “Wolf,” and sometimes, though less appropriately, “Hyaena.” Owing to the havoc it commits among the sheepfolds, it has been nearly exterminated in all the more settled parts of Tasmania, but still finds shelter in the almost impenetrable rocky glens of the more mountainous regions of the island. The female produces four young at a time.

Dasyurus.— Dentition: i ⅜, c ⅜, p ⅜, m ⅜; total 42. Upper incisors nearly equal, and placed vertically. In the smaller species the first is slightly longer, narrower, and separated from the rest. Lower incisors nearly vertical in the larger, but sloping forwards and upwards in the smaller species. Canines large and sharply pointed. Premolars, in the typical forms, with compressed and sharp-pointed crowns, and slightly developed anterior and posterior accessory basal cusps. True molars with numerous sharp-pointed cusps. In the upper jaw the first three with crowns having a triangular free surface, the fourth small, simple, narrow, and placed transversely. In the lower jaw the molars more compressed, with longer cusps; the fourth not notably smaller than the others. Ears of moderate size, prominent, and obtusely pointed. Hallux rudimentary, clawless, or absent; its metatarsal bone always present. Tail generally long and well clothed with hair. Vertebrae :C 7, D 13, I. 6, 8 2, C 18-20. The true Dasyures are mostly inhabitants of the Australian continent and Tasmania, where in the economy of nature they take the place of the smaller predaceous Carnivora, the Cats, Civets, and Weasels of other parts of the world. They hide themselves in the daytime in holes among rocks or in hollow trees, but prowl about at night in search of the small living mammals and birds which constitute their prey. .The species are not numerous, and divide themselves into two sections. (1) Dasyurus proper includes D. maculatus, about the size of a common Cat, inhabiting Tasmania and the southern part of Australia; D. viυerrinus or maugei, Tasmania and Victoria; D. geoffroyi, South Australia; D. hallucatus, North Australia; D. albopunctatus, New Guinea. (2) Sarcophilus contains one species, D. ursinus, differing from the others in being a larger and heavier animal, with a disproportionally large and broad head. Its teeth are relatively larger and more massive, and hence more crowded in the jaws; the premolars especially are scarcely compressed but rather conical; the lower molars want a cusp placed near the middle of the inner border, found developed in different degrees in all the species of the first section. This animal is peculiar to Tasmania, where it is commonly known by the name of “Devil.” Its prevailing colour is black, its size about that of an English Badger, and its disposition remarkably savage and voracious.

Phascogale.— This genus (more properly Phascologale) comprises a considerable number of small Marsupials, none of them exceeding a common Rat in size, differing from the true Dasyures in possessing an additional premolar,—the dentition being i ⅜, c⅛, p⅜, m ⅜; total 46, —and having the teeth generally developed upon an insectivorous rather than a carnivorous pattern, the upper middle incisors being larger and inclined forwards, the canines relatively smaller, and the molars with broad crowns, armed with prickly tubercles. The muzzle is pointed. Ears moderately rounded and nearly naked. Fore feet with five subequal toes, with compressed, slightly curved pointed claws. Hind feet with the four outer toes subequal, with claws similar to those in the fore feet; the hallux almost always distinct and partially opposable, though small and nailless, sometimes absent. The food of these animals is almost entirely insects, which some pursue among the branches of trees, while others are purely terrestrial. They are found throughout Australia, and also in New Guinea and the Aru and some of the adjacent islands. Variations in the details of the dentition and of the structure of the hind limbs, and in the length and arrangement of the hairy covering of the tail, have given rise to several subdivisions which will probably be accepted as generic by most zoologists, although further investigations are required before their limits can be very satisfactorily defined.

P. cristicauda, a species with a thick compressed tail ornamented upon its apical half with a crest of black hair, differs from the others by the very reduced size of the third premolar in the upper and its complete absence in the lower jaw, thus forming an interesting transition in dentition towards Dasyurus. It constitutes the genus Chaetocercus of Krefft. Another very aberrant form, P. lanigera, distinguished by the great elongation of the fore arm and hind foot, and the complete absence of hallux, is Antechinomys of the same author. It is an elegant little terrestrial mouse-like animal, with large oval ears aud long tail with the terminal part bushy. Antichinus and Podabrus are names proposed for other divisions of the group.

Subfamily Myrmecobiinae.—Molars and premolars exceeding the normal number of seven on each side. Tongue long and extensile.

Myrmecol>ius.— Dentition: i ⅜, c ⅜,p ⅜, m ⅜ or ⅜; total 52 or 54, being the largest number of teeth in any existing Marsupial. The distinction between the molars and premolars is not certain, as it is not founded on a knowledge of the succession of the teeth, but on their form. The teeth are all small and (except the four posterior inferior molars) separated from each other by an interval. Head elongated, but broad behind. Muzzle long and pointed. Ears of moderate size, ovate, and rather pointed. Fore feet with five toes, all having strong, pointed, compressed claws, the second, third, and fourth nearly equal, the fifth somewhat and the first considerably shorter. Hind feet with no trace of hallux externally, but the metatarsal bone is present. Tail long, clothed with long hairs. Fur rather harsh and bristly. Female without any trace of a pouch, the young when attached to the nipples being concealed only by the long hair of the abdomen. Vertebrae: C 7, D 13, I. 6, S3, C23.

Of this singular genus but one species is known, Μ. fasciatus, found in western and southern Australia. It is about the size of an English squirrel, to which animal its long bushy tail gives it some resemblance; but it lives entirely on the ground, especially in sterile, sandy districts, feeding on ants. Its prevailing colour is chestnut-red, but the hinder part of the back is elegantly marked with broad, white, transverse bands on a dark ground.

Family Peramelidae.

Dentition: i ⅞, c ∣ , p ⅜, m f; total 48. Upper incisors small, with short, broad crowns. Lower incisors moderate, narrow, proclivous. Canines well developed. Premolars compressed, pointed. Molars with quadrate tuberculated crowns. Third premolar preceded by a very minute molaτiform tooth, which remains in place until the animal is nearly full grown. Fore feet with two or three of the middle toes of nearly equal size, and provided with strong, sharp, slightly curved claws; the other toes rudimentary. Hind feet long and narrow; the hallux rudimentary or absent; the second and third toes very slender, and united in a common integument; the fourth very large, with a stout elongated conical claw; the fifth smaller than the fourth (see fig. 29). The ungual phalanges of the large toes of both feet cleft at their extremities (as in Manis among the Edentata, but in no other Marsupials). Head elongated. Muzzle long, narrow, and pointed. Stomach simple. Caecum of moderate size. Pouch complete, generally opening backwards. Alone among Marsupials they have no clavicles.

The Peramelidae form a very distinct family, in some respects intermediate between the sarcophagous Dasyuridae and the phytophagous Macropodidae. In dentition they resemble the former, but they agree with the latter in the peculiar structure of the hind feet. In the construction of the fore feet they differ from all other Marsupials. They may be divided into three genera.

Perameles.— Anterior and posterior extremities not differing greatly in development. Fore feet with three middle toes well developed, the third slightly larger than the second, the fourth somewhat shorter, provided with long, strong, slightly curved, pointed claws. First and fifth toes very short and without claws’ Hind feet with hallux of one or two phalanges, forming a distinct tubercle visible externally; the second and third toes very slender, of equal length, joined as far as the ungual phalanx, but with distinct claws; the fifth intermediate in length between these and the largely developed f⅛urth toe. Ears of moderate or small size, ovate, pointed. Tail rather short, clothed with short adpressed hairs. Fur short and harsh. Pouch opening backwards. Vertebrae: C7, D13, L6, Si, C17.

The animals of this genus, commonly called “Bandicoots” in Australia, are all small, and live entirely on the ground, making nests composed of dried leaves, grass, and sticks in hollow places. They are rather mixed feeders; but insects, worms, roots, and bulbs constitute their ordinary diet. The various species are widely distributed over Australia, Tasmania, New Guinea, and several of the adjacent islands, as Aru, Kei, and New Ireland. The best known are— P. fasciata, gunnii (fig. 28), myosurus, nasuta, obesula, and macrura from Australia, and P. doreyana, saffrayana and longicauda from New Guinea.

Macrotis.— Molar teeth curved, and with longer crowns and shorter roots than in the last. Hinder extremities proportionally longer, and hallux represented only by a small metatarsal bone. Muzzle much elongated and narrow. Fur soft and silky. Ears very large, long, and pointed. Tail long, its apical half clothed on the dorsal surface with long hairs. Pouch opening forwards. Vertebrae: C 7,.D 13, I. 6, S 2, C23.

But one species is known, Μ. lagotis, from western Australia. It is the largest member of the family, being about the size of the common Rabbit, to which animal it bears sufficient superficial resemblance to have acquired the name of “Native Rabbit” from the colonists. It burrows in the ground, but in other respects resembles the Bandicoots in its habits.

Chaeropus. — Dentition generally resembling that of Perameles, but the canines are less developed, and in the upper jaw two-rooted. Limbs very slender; posterior nearly twice the length of the anterior. Fore feet with the functional toes reduced to two, the second and third, of equal length, with closely united metacarpals and short, sharp, slightly curved, compressed claws. First toe represented by a minute rudiment of a metacarpal bone; the fourth by a metacarpal and two small phalanges without a claw, and not reaching the middle of the metacarpal of the third; fifth entirely absent. Hind foot long and narrow, mainly composed of the strongly developed fourth toe, terminating in a conical pointed nail, with a strong pad behind it; the hallux represented by a rudimentary metatarsal; the remaining toes completely developed, and with claws, but exceedingly slender; th e un ited second and th ird reaching a little way beyond the metatarso-phalangeal articulation of the fourth; the fifth somewhat shorter. Tail not quite so long as the body, and covered with short hairs. Ears large and pointed, and folded down when the animal is at rest. Fur soft and loose. Pouch opening backwards. Vertebrae: C 7, D13, I. 6, S1, C 20.

The only known species of this genus, chiefly remarkable for the singular construction of its limbs, is an animal about the size of a small Rat, found, in the interior of the Australian continent. Its general habits and food appear to resemble those of the other Peramelidae. It was first described as C. ecaudatus by Ogilby from a mutilated specimen, but the specific name was afterwards changed by Gray to castanotis. Family Macropodidae.

The general characters of this family, and an account of the animals composing it, will be found in the article Kangaroo, vol. xiii. p. 838 sq. Family Phalangistidae.

Dentition (except in the aberrant genus Tarsipes')·. i f, the first above strong, curved, and cutting, the other two generally somewhat smaller; the single lower incisor large, more or less proclivous; c 1 -⅛ r -p, upper small or moderate, conical and harp-pointed; lower absent or quite rudimentary; p i ^ , variable; m ⅜ or ⅞, with four obtuse tubercles. Limbs subequal. Fore feet with five distinct, subequal toes with claws. Hind feet, short and broad, with five well-developed toes; the hallux large, nailless and opposable; the second and third slender and united by a common integument as far as the claws. Stomach simple. Caecum present (except in Tarsipes), and usually large. Pouch complete. Animals of small or moderate size and arboreal habits, feeding on vegetable or mixed diet, inhabiting Australia and the Papuan Islands. Excluding Phascolarctos and especially Tarsipes, they form a very natural family. The latter is, however, evidently a modified form of the same general type, chiefly aberrant in the characters of its alimentary organs, which are adapted for a peculiar mode of subsistence. It may constitute a distinct subfamily.

Subfamily Tarsipedinae. —Teeth almost rudimentary and variable in number. Tongue long, slender, pointed, and very extensile. Caecum absent.

Tarsipes.— This is named from some supposed resemblance of its foot to that of the Lemurine genus Tarsius ; but it must be remarked that it has none of the peculiar elongation of the calcaneum and scaphoid so characteristic of that genus. Head with elongated and slender muzzle. Mouth opening small. The two lower incisors are long, very slender, sharp-pointed, and horizontally placed. All the other teeth are simple, conical, minute, and placed at considerable and irregular intervals apart in the jaws, the number appearing to vary in different individuals and even on different sides of the two individuals. The formula in a specimen in the Museum of the Royal College of Surgeons is i j∈∣, c ~, p and m ∣∈∣; total 20. Rami of the mandible extremely slender, nearly straight, and without coronoid process or inflected angle. Fore feet with five well-developed toes, with small, flat, scale-like nails, not reaching to the extremity of the digits. Hind feet rather long and slender compared with that of the Phalangistinae, with well-developed opposable and nailless hallux; second and third digits syndactylous, with sharp compressed curved claws; the fourth and fifth free, and with small flat nails. Ears of moderate size and rounded. Tail longer than the body and head, scantily clothed with short hairs, prehensile. Vertebra: C 7, D13, I. 5, S3, C 24.

Of this singular genus but one species, T. rostratus (fig. 31), is known, about the size of a common Mouse. It inhabits western Australia, lives in trees and bushes, uses its tail in climbing, and feeds on honey, which it procures by inserting its long tongue into the blossoms of Mel deucse, he. One kept in confinement by Mr Gould was also observed to eat flies.

Subfamily Phalangistinae.

Teeth normal. Rudimentary lower canines present. Tongue of ordinary structure. No cheek pouches. Stomach and ascending colon simple. Caecum long, simple. Tail well-developed.

A numerous group, varying in size from that of a Mouse to a large Cat, arboreal in their habits, and abundantly distributed throughout the Australian region. One section is distinguished by the possession of a flying membrane, or fold of skin, extending on each side of the body between the fore and hind legs, forming when the limbs are extended a kind of parachute, as in the Flying Squirrels, and also by a non-prehensιle tail. This includes the genera Γc taurus, Belideus, and Acrobata. The remainder have no such membrane, and have the tail more or less prehensile, the under surface at least of the apical portion being bare. These are the typical Phalangers, or “Opossums” as they are commonly called in Australia (genus Phalangista), and their various modifications, as Cuscus, Pseudochirus, and Dactylopsila. These will be more fully described in the article Phalanger.

Subfamily Phascolarctinae.—Teeth normal; no rudimentary lower canines. Tongue of ordinary structure. Distinct cheek pouches. Stomach with a special gland near the cardiac orifice. Caecum very long, and (with the upper portion of the colon) dilated and provided with numerous longitudinal folds of mucous membrane. In many anatomical characters, especially the possession of a special gastric gland, this group resembles the Phasco- lomyidae, to which it obviously forms a transition. Phascolarctos. — Dentition: if, c ⅜, p ⅜, m ⅜; total 30. Upper incisors crowded together, cylindroidal, the first much larger than the others, with a bevelled cutting edge (fig. 25). Canine very small; a considerable interval between it and the premolar, which is as long from before backwards ^ but not so broad as the true molars, and has a cutting edge, with a smaller parallel inner ridge. The molars slightly diminishing in size fr*m the first to the fourth, with square crowns, each bearing four pyramidal cusps. The lower incisors are semiproclivous, compressed and tapering, bevelled at the ends. Premolars and molars in continuous series, as in the upper jaw. Fore feet with the two inner toes slightly separated from and opposable to the remaining three, all with strong, curved, and much compressed claws. Hind foot with the hallux placed very far back, large and broad, the second and third (united) toes considerably smaller than the other two; the fourth the largest. No external tail. Fur dense and woolly. Ears of moderate size, thickly clothed with long hairs. Vertebrae: C 7, Dll, I. 8, S 2, C 8. Ribs eleven pairs, a rare exception to the usual number (13) in the Marsupialia.

There is but one species, the Koala or Native Bear of the Australian colonists (P. cinereus), found in the south-eastern parts of the Australian continent. It is about 2 feet in length, and of an ash-grey colour, an excellent climber, and residing generally in lofty Eucalyptus trees, on the buds and tender shoots of which it feeds, though occasionally descending to the ground in the night.

Kindred Fossil Forms.

Here may be noticed several genera of extinct Marsupials, the remains of which have been found in the post-Tertiary deposits of Australia, which agree with the Macropodidae and the Phalangistidae in having ⅜ incisors, those of the lower jaw very large and proclivous. As the whole of their structure, especially that of the hind feet, is not yet known, their precise affinities cannot be determined.

Diprotodon.— Dentition: i f, c ⅜, p f, m ⅜; total 28. The first upper incisor very large and scalprifoιτn. True molars with prominent transverse ridges, as in Macropus, but wanting the longitudinal connecting ridge. Anterior and posterior limbs less disproportionate than in the Kangaroos. 7). australis is a gigantic animal compared with all existing Marsupials, surpassing a Rhinoceros in bulk.

Nototherium.— Dental formula as in the last, from which it differs chiefly in the incisor teeth, especially those of the lower jaw, being much smaller. The skull is short, with the zygomatic arches extremely broad. TV. mitchelli and inerme, both animals of great size, though inferior to Diprotodon. Thylacoleo.— Dentition of adult: i f, c ⅜, p ⅞, m total 24. First upper incisor much larger than the others; canine and first two premolars rudimentary. In the lower jaw there are also one or two small and early deciduous premolars; posterior premolars of both jaws formed on the same type as that of Hypsiprymnus, but relatively much larger; true molars rudimentary, tubercular. One species, T. carnifex. This animal presents a most anomalous condition of dentition, the functional teeth being reduced to one pair of large cutting incisors situated close to the median line, and one great, trenchant, compressed premolar, on each side above and below. It was first described as a carnivorous Marsupial, and named, in accordance with its presumed habits, “as one of the feilest and most destructive of predatory beasts but, as its affinities are certainly with the Phalangistidae and Macropodidae, and its dentition completely unlike that of any known predaceous animal, this view has been called in question. Family Phascolomyidae.

Dentition: c ∣, i ⅞, p ⅜, m ⅜ = 24. All the teeth with persistent pulps. The incisors large, scalpriform, with enamel only on the front, surface, as in the Rodentia. The molars strongly curved, forming from the base to the summit about a quarter of a circle, the concavity being directed outwards in the upper and inwards in the lower teeth. The first of the series (generally called “premolar,” though it appears to have no milk predecessor) single-lobed; the other four composed of two lobes, each subtriangular in section. Limbs equal, stout, and short. Fore feet with five distinct toes, each furnished with a long, strong, and slightly curved nail, the first and fifth considerably shorter than the other three. Hind feet with a very short nailless hallux, the second, third, and fourth toes partially united by integuments, of nearly equal length, the fifth distinct and rather shorter; all four provided with long and curved nails. In the skeleton of the foot, the second and third toes are distinctly more slender than the fourth, showing a slight tendency towards the peculiar character so marked in the last three families. Tail rudimentary. Stomach simple, provided with a special gland situated near the cardiac orifice. Caecum very short, wide, and with a peculiar vermiform appendage.

The species of this family are few, and all contained in one genus, Phascolomys, with two well-marked sections, one containing the Common and Broad-nosed Wombats, P. wombat anà.platyrhinus, the other the Hairy-nosed Wombat, P. latifrons. They are all terrestrial and burrowing animals, generally slow in their movements, and harmless in disposition; they feed on roots and other vegetable substances, and inhabit the southern parts of the Australian continent, Tasmania, and the islands of Bass’s Straits. See Wombat. Bibliography of Marsupials.— G. R. Waterhouse, Nat. Hist, of the Mammalia, vol. 1. “Marsupiata,” 1846; J. Gould, Mammals of Australia, 1863; R. Owen, article “Marsupialia," in Cyclop, of Anatomy and Physiology, and various memoirs “On Extinct Mammals of Australia" in Philosophical Transactions·, W. II. Elower, “On the Development and Succession of the Teetlι in the Marsupialia,” Phil. Trans., 1867.

Subclass EUTHERIA or MONODELPHIA.

The remaining mammals are included, in the Eutheria, Placentalia, or Monodelphia, the leading characters of which have been given at p. 372. Their affinities with one another are so complex that it is impossible to arrange them satisfactorily in any serial order. The Edentata may be taken first as standing in some respects apart from all the others. The Sirenia and Cetacea are also somewhat isolated, having undergone most remarkable modifications from the normal mammalian type. The Primates must be placed at the head of the series. The position of the others is quite arbitrary, as none of the hitherto proposed associations of the orders into larger groups stand the test of critical investigation, and palaeontological researches have already gone far to show that they are all modifications of a common heterodont, diphyodont, pentadactyle form.

Order EDENTATA.

The name assigned to this group (which some zoologists think ought rather to be ranked as a subclass than an order) by Cuvier is often objected to as inappropriate, for though some of the members are edentulous, others have very numerous teeth; and the Linnaean name Bruta is occasionally substituted. But that term is quite as objectionable, especially as the group to which Linnaeus applied it is by no means equivalent to the order as now understood, as the names of the genera contained in it, viz., Elephas, Trichechus, Bradypus, Myrmecophaga, Manis, and Dasypus, will indicate. It contained, in fact, all the animals then known which are comprised in the modern orders of Probosddea, Sirenia, and Edentata, together with the Walrus, one of the Carnivora. If retained at all, it should rather belong to the Probosddea, as Elephas stands first in the list of genera, and was probably in the mind of Linnaeus when he assigned the name to the group. Cuvier’s order included the Ornithorhynchus and Echidna, the structure of which was then imperfectly known, and which are now by common consent removed to an altogether different section of the class, but otherwise its limits are those now adopted. The name Edentata is so generally used, and its meaning so well understood, that it would be very undesirable to change it now; in fact similar reasons might be assigned for ceasing to use nearly all the other current ordinal designations, for it might be equally well objected that all the Carnivora are not flesheaters, many of the Marsupialia have not pouches, and so forth.

If the teeth are not always absent, they invariably exhibit certain imperfections, which are indeed almost the only common characters which bind together the various extinct and existing members of the order. These are—that they are homodont and, with the remarkable exception of the genus Tal·usia, monophyodont; they are never rooted but have persistent pulps; they are always deficient in one of the constituents which enter into the formation of the complete mammalian tooth, the enamel, and are never present either in the upper or lower jaw in the fore part of the mouth, the situation occupied by the incisors of other mammals.

There is so great a difference in structure and habits between some of the existing animals assigned to this order that, beyond the negative characters just mentioned, there seems little to connect them. The Sloths and Anteaters, for instance, in mode of life, general conformation of limbs, structure of digestive organs, &c., appear at first sight almost as widely separated as any mammals. Palaeontology has, however, thrown great light upon their relations, and proved their real affinities. Perfectly intermediate forms have been discovered in the great Ground Sloths of America, which have the dentition and general form of the head of the Sloths, combined with the limbs and trunk of the Anteaters. It is highly probable that the existing members of the order are very much differentiated representatives of a large group, the greater number of which are now extinct, and which have become so without ever attaining a high grade of organization. The great diversity of structure of the existing families, the high degree of specialization to which many have attained, the paucity of species and even of individuals, their limited area of distribution, and their small size compared with known ancestral forms, all show that this is an ancient and a waning group, the members of which seem still to hold their own either by the remoteness and seclusion of their dwelling-places, by their remarkable adaptation of structure to special conditions of life, or by aid of the peculiar defensive armature with which they are invested. Their former history can, however, only be thus surmised, rather than read, at present; for, though we have ample evidence of the abundance and superior magnitude of certain forms in the most recent or post-Tertiary geological age, and in one part of the world, beyond this time, i.e., in the true Tertiary period, and in other parts of the world than America, the remains of animals of this order hitherto discovered are only fragmentary, giving a most imperfect idea of their actual structure, and affording no indications which serve to connect them with any other branch of the class.

The existing members of the order readily group themselves into five distinct families, the limits of which are perfectly clear. These are (1) Bradypodidae, or Sloths; (2) Myrmecophagidae, or Anteaters; (3) Dasypodidae, or Armadillos; (4) Manidae, Pangolins or Scaly Anteaters; and (5) Orycteropodidae, Aard-varks or African Anteaters. The geographical distribution of these families coincides with their structural distinction, the first three being inhabitants of the New and the last two of the Old World. It has been usual to arrange these families into two large groups or suborders :—(1) the Phyllophaga, leaf-eaters, also called Tardigrada, containing the Bradypodidae alone; and (2) the Entom,ophaga, insect-eaters, or Vermilingua, containing all the other families, from which sometimes the Orycteropodidae are separated as a third suborder under the name of Effodientia. Such an arrangement is, however, an artificial one, founded on superficial resemblance. The bonds which unite the Manidae to the Myrmecophagidae are mainly to be found in the structure of the mouth, especially the extensile character of the tongue, the great development of the submaxillary glands, and the absence of teeth. These characters are exactly analogous to those found in the Echidna among Monotremes, the Woodpeckers among Birds, and the Chamaeleon among Reptiles,—the fact probably being that in countries where Termites and similar insects flourish various distinct forms of vertebrates have become modified in special relation to this abundance of nutritious food, which could only be made available by a peculiar structure of the alimentary organs. A close study of the more essential portions of the anatomy of these animals leads to the belief that all the American Edentates at present known, however diversified in form and habits, belong to a common stock. The Bradypodidae, Megathe- riidae, and Myrmecophagidae are closely allied, the modifications seen in the existing families relating only to food and manner of life. The ancestral forms may have been omnivorous, and gradually separated into the purely vegetable and purely animal feeders; from the former are developed the modern Sloths, from the latter the Anteaters. The Armadillos (Dasypodidae) are another modification of the same type, retaining some generalized characters, as those of the alimentary organs, but in other respects, as their defensive armature, remarkably specialized. The two Old-World families Manidae and Orycteropodidae are so essentially distinct, both from the American families and from each other, that it may even be considered doubtful whether they are derived from the same primary branch of mammals, or whether they may not be offsets of some other branch, the remaining members of which have been lost to knowledge.

Family Bradypodidae.

Externally clothed with long, coarse, crisp hair. Head short and rounded. External ears inconspicuous. Teeth f in each jaw, subcylindrical, of persistent growth, consisting of a central axis of vaso-dentine, with a thin investment of hard dentine, with a thick outer coating of cement; without (as far as is yet known) any succession. Fore limbs greatly longer than the hind limbs. All the extremities terminating in narrow, curved feet; the digits never exceeding three in number, encased for nearly their whole length in a common integument, and armed with long strong claws. Tail rudimentary. Stomach complex. No caecum. Placenta deciduate, dome-like, composed of an aggregation of numerous discoidal lobes. Strictly arboreal in habits, vegetable feeders, and limited geographically to the forest regions of South and Central America. Two genera, Bradypus and Choloepus. See Sloth. Family Megatheriidae.

The members of this family are all extinct. Their characters, so far as is known from the well-preserved remains of many species found abundantly in deposits of Pleistocene age in both North and South America, were intermediate between those of the existing Bradypodidae and the Myrmecophagidae, combining the head and dentition of the former with the structure of the vertebral column, limbs, and tail of the latter. Almost all the known species are of comparatively gigantic size, the smallest, Coelodon escriυan-ensis, exceeding the largest existing Anteater, and the Megatherium being larger than a Rhinoceros. The dentition is usually f on each side, as in the Sloths, but in Coelodon ⅜. This genus, and in a still more marked degree Megatherium, differ from all the others in the details of the structure of the teeth. They are very deeply implanted, of prismatic form (quadrate in transverse section); and the component tissues—hard dentine (fig. 35, d), softer vaso-dentine (v), and cementum (c)—are so arranged that, as the tooth wears, the surface always presents a pair of transverse ridges, thus producing a triturating apparatus comparable to the “bilophodont” molar of Dinotheruιm, Tapirus, Manatus, Macropus, and others, though produced in a different manner. In all the other genera the teeth are more or less cylindrical, though sometimes laterally compressed or even longitudinally grooved on the sides, and on the grinding surface the prominent ridge of hard dentine follows the external contour, and is surrounded only by a thin layer of cementum, as in the existing Sloths. The genera of which the remains are best known are Mylodon (fig. 37), Lesto-don, Scelidotherium, Gryphotherium, and Megalonyx. In the last-named the anterior tooth of both upper and lower jaws is large and removed by a considerable interval from the others. The osteological characters of these genera have been fully described in the works of Cuvier, Owen, Burmeister, Leidy, Gervais, Reinhardt, and others.

No Eocene Edentates have yet been found in America. In the Miocene of the Pacific coast of North America some remains have been discovered, assigned by Marsh to the genus Moropus, the type of a distinct family, the Moropidae. There are two species, one about as large as a Tapir, and one nearly twice that size. In the Lower Pliocene, well-preserved remains of Edentates of very large size have been found at several widely separated localities in Idaho and California. These belong to the genus Morotherium, of which two species are known. East of the Rocky Mountains, in the Lower Pliocene of Nebraska, a large species apparently of the genus Moropus has been discovered. None of these have as yet been fully described or figured. Marsh believes that North America was the original home of the Edentates, and that they spread to the southern portion of the continent towards the close of the Tertiary period.

Family Myrmecophagidae.

Externally clothed with ħair. No teeth. Head elongated. Mouth tubular, with a small terminal aperture, through which the long, vermiform tongue, covered with the viscid secretion of the enormous submaxillary glands, is rapidly protruded in feeding, and withdrawn again with the adhering particles of aliment, which are then sucked into the pharynx. In the maùus, thé third toe is greatly developed, and has a long falcate claw; the others are reduced or suppressed. The pes has lour or five subequal digits with claws. Posterior dorsal and lumbar vertebrae with additional interlocking zygapophyses. Tail long, sometimes prehensile. Placenta dome-like or discoidal. The animals of this family are the ‘ t Anteaters "par excellence. They feed exclusively on animal substances, mostly insects. One species is terrestrial, the others arboreal; none burrow in the ground. They are all inhabitants of the Neotropical region.

Myrmecophaga.— Skull greatly elongated and narrow, its upper surface smooth and cylindriform. Anteriorly the face is produced into a long, tubular rostrum, rounded above and flattened below, and with terminal nares, and composed of the mesethmoid ossified for more than half its length, the vomer, the maxillae, and the long and narrow nasal bones, the premaxillae being extremely short and confined to the margin of the anterior nares. The zygomatic arch is incomplete, the styliform malar only articulating with the maxilla in front, and not reaching to the very short zygomatic process of the squamosal. The lacrymal foramen is in front of the margin of the orbit. There are no post-orbital processes to the frontals or any other demarcation between the orbits and the temporal fossae. Palate extremely elongated, and produced backwards as far as the level of the external auditory meatus by the meeting in the middle line of the largely developed pterygoids. The glenoid fossa a shallow oval facet, with its long diameter from before backwards. Mandible very long and slender, with an exceedingly short symphysis, no distinct coronoid process, and a slightly elevated, elongated, flattened, condylar articular surface. Vertebrae: 0 7, D 15-16, I. 3-2, S 6, C 31. Clavicles rudimentary. In the manus, the first digit is very slender, the second also slender, with compressed phalanges of nearly equal length. The third digit is immensely developed; though its proximal phalanx is extremely short, its ungual phalanx is so long that the entire length of the digit exceeds that of the second. The fourth has a long and rather slender metacarpal, and three phalanges diminishing in size, the ungual phalanx being very small. The fifth has the metacarpal nearly as long, but not so stout as the fourth, and followed by two small phalanges, the last rudimentary and conical. Claws are developed upon all but the fifth. In walking the toes are kept strongly flexed, and have their points turned upwards and inwards, the weight being supported upon a callous pad over the end of the fifth digit, and by the dorsal surfaces of the third and fourth digits. The hind feet are short and rather broad, with five subequal claws, the fourth rather longest, the first shortest; the whole sole is placed on the ground in walking. Body rather compressed, clothed with long, coarse hair. Tail about as long as the body, and covered with very long hair; not prehensile. Ears small, oval, erect. Eyes very small. Stomach consisting of a subglobular, thin-walled, cardiac portion, and a muscular pyloric gizzard with dense epithelial lining. No ileocolic valve, and a short wide ill-defined caecum. Mammae two, pectoral.

There is one species, Μ. jubata, the Great Anteater, or Ant Bear, measuring 4 feet in length without the tail, and upwards of 2 feet in height at the shoulder. Its prevailing colour is grey, with a broad black band, bordered with white, commencing on the chest, and passing obliquely over the shoulder, diminishing gradually in breadth as it approaches the loins, where it ends in a point.

It is extensively distributed in the tropical parts of South and Central America, frequenting low swampy savannas, along the banks of rivers, and the depths of the humid forests, but is novyhere abundant. Its food consists mainly of termites, to obtain which it opens their nests with its powerful sharp anterior claws, and as the insects swarm to the damaged part of their dwelling, it draws them into its mouth by means of its long, flexible, rapidly-moving tongue covered with glutinous saliva. The Great Anteater is quite terrestrial in its habits, being never known to climb trees, nor does it burrow underground like the Armadillos. Though generally an inoffensive animal, when attacked it can defend itself vigorously and effectively with its sabre-like anterior claws. The female bears but a single young at a birth.

Tamandua.— This genus closely resembles the last in anatomical structure, but the head is much less elongated, the fur is short and bristly, the tail, tapering, prehensile, with the under side throughout and the whole of the terminal portion naked and scaly. The stomach is similar to that of Myrmecophaga, but with the muscular pyloric gizzard not quite so strongly developed. There is a distinct ileo-colic valve and short globular caecum. The fore foot has a very laτge claw on the third toe, moderate-sized claws on the second and fourth, a very minute one on the first, and none on the fifth, which is entirely concealed within the skin. The hind foot has five subequal claws. Vertebrae: C 7, D 17, I. 2, S 5, C 37. There are very rudimentary clavicles.

The Tamandua {T. tciradactyla) is much smaller than the Great Anteater, and differs essentially from it in its habits, being mainly arboreal. It is an inhabitant of the dense primeval forests of South and Central America. As different individuals vary much in their coloration, it is possible that there may be more than one species. The usual colour is yellowish-white, with a broad black lateral band, covering nearly the whole of the side of the body.

Cycloturus.— The skull is much shorter even than in Tamandua, and is arched considerably in the longitudinal direction. It differs from that of the other members of the family mainly in the long canal for the posterior nares not being closed by bone below, as the greater part of the palatines and the pterygoids do not meet in the middle line. The mandible has a prominent, narrow, recurved coronoid and a well-developed angular process; it is strongly decurved in front. Vertebrae: C 7, D 16, I. 2, S 4, C 40. Ribs remarkably broad and flat. Clavicles well developed. Manus remarkably modified. The third digit is greatly developed at the expense of all the others; it has a stout short metacarpal and but two phalanges, of which the most distal is large, compressed, pointed, and much curved, and bears a very strong hook-like claw. The second digit has the same number of phalanges, and bears a claw, but is very much more slender than the third. The fourth is represented only by the metacarpal, and one nailless phalanx, the first and fifth only by very rudimentary metacarpals. The pes is also completely modified into a climbing organ. The hallux is rudimentary, consisting of a metatarsal and one phalanx, concealed beneath the skin, but the other four toes are subequal and much curved, with long pointed compressed claws. The tuber calcanei is directed towards the plantar surface, and parallel with it and extending to about double its length is a greatly elongated sesamoid ossicle. These together support a prominent calcarine cushion to which the nails are opposed in climbing. Stomach pyriform, with muscular walls, but no distinct gizzard-like portion, as in the foregoing genera. The commencement of the colon provided with two small caeca, resembling those of many Birds, narrow at the base, and rather dilated at their terminal blind ends, and communicating with the general cavity by very minute apertures. Tail longer than the body, tapering, bare on the under surface, and very prehensile. Fur soft and silky.

This genus has also but one species certainly known, the Little or Two-toed Anteater (C ’. didactylus), an animal not larger than a Rat, of a general yellowish colour, and exclusively arboreal in its habits. It is a native of the hottest parts of South and Central America.

Family Dasypodidae.

The greater part of the skin strongly ossified. On the back and sides the union of numerous quadrate or polygonal scutes forms a hard shield, usually consisting of an anterior (scapular) and posterior (pelvic) solid portion (which overhang on each side the parts of the body they respectively cover, forming chambers into which the limbs are withdrawn), and a variable number of rings between, connected by soft flexible skin so as to allow of curvature of the body. The top of the head has also a similar shield (cephalic), and the tail is usually encased in bony rings or plates. The outer or exposed surfaces of the limbs are protected by irregular bony scutes, not united at their margins; but the skin of the inner surface of the limbs and under side of the body is soft and more or less clothed with hair. Hairs also in many species project through apertures between the bony scutes of the baςk. The ossified dermal plates are everywhere covered by a layer of horny epidermis. Teeth numerous, simple, of persistent growth, and usually monophyodont, but in one genus (Tatusia) a succession of teeth has been observed. Zygomatic arch of skull complete. Cervical vertebrae with extremely short, broad, and depressed bodies. The atlas free, but the second and third, and often several of the others, ankylosed together both by their bodies and arches. Lumbaι∙ vertebrae λvith accessory zygomatic processes, and very large metapophyses, supporting the bony carapace. Clavicles well developed. A third trochanter on the femur. Tibia and fibula ankylosed at their distal extremities. Fore feet with strongly developed, curved claws, adapted for digging and scratching, three, four, or five in number. Hind feet plantigrade, with five toes, all provided with nails. Tongue long, pointed, and extensile, though to a less degree than in the Anteaters. Submaxillary glands largely developed. Stomach simple. Placenta discoidal, deciduate.

The animals of this family are commonly called Armadillos, a word of Spanish origin, having reference to their armour-like covering. The existing species are all of small or moderate size. They are mostly, though not universally, nocturnal in their habits. They are omnivorous, feeding on roots, insects, worms, reptiles, and carrion. They are harmless and inoffensive creatures, offering no resistance when caught, their principal means of escape from their enemies being the extraordinary rapidity with which they can burrow in the ground, and the tenacity with which they retain their hold in their subterranean retreats. Notwithstanding the shortness of their limbs they can run with great rapidity. Most of the species are esteemed good eating by the natives of the countries in which they live. They are all inhabitants of the open plains or the forests of the tropical and temperate parts of South America, with the exception of one species (Tatusia peba), which ranges as far north as Texas. Of the existing genera, Chlamydophorus stands apart from the rest in the formation of its external covering; but in all other respects Tatusia is the most aberrant form, exhibiting a different type of structure of the fore feet, which in all the others shows modifications, though in very varying degrees, of the same type.

Subfamily Chlamydophorinae.—In most anatomical characters, especially the structure of the fore foot, this little group resembles the Dasypodinae, but it differs remarkably from all other known Armadillos, living or extinct, in the peculiar modification of the dermal armour.

Chlamydophorus.— Teeth ~ 9 , subcylindrical, somewhat compressed, moderate in size, smaller at each end (especially in front) than at the middle of the series. Skull broad and rounded behind, pointed in front. Muzzle subcylindrical and depressed. A conspicuous rounded, rough prominence on the frontal bone, just before each orbit. Tympanic prolonged into a tubular auditory meatus, curving upwards round the base of the zygoma. Vertebrae: C 7, D 11, I. 3, S 10, C 15. Upper part of head and trunk covered with four-sided homy plates (with very small thin ossifications beneath), forming a shield, free, and overhanging the sides of the trunk, and attached only along the middle line of the back. The plates are arranged in a series jot distinct transverse bands, about twenty in number between the occiput and the posterior truncated end, and nol divided into solid thoracic and pelvic shields with movable bands between. The hinder end of the body is abruptly truncated and covered by a vertically-placed, strong, solid, bony shield, of an oval (transversely extended) form, covered by thin epidermic plates. This shield is firmly ankylosed by five bony processes to the lιindeι part of the pelvis. Through a notch in the middle of its loweι border the tail passes out. The latter is rather short, cylindrical in its proximal half, and expanded and depressed or spatulate in its terminal portion, and covered with horny plates. The dorsal surfaces of the fore and hind feet are also covered with horny plates. The remainder of the limbs and under surface and sides of the bodj beneath the overlapping lateral parts of the dorsal shield are clothed with rather long, very soft silky hair. Eyes and ears very small, and concealed by the hair. Extremities short. Feet large, each with five well-developed claws, those on the fore feet very long, stout, and subcompressed, the structure of the digits being essentially the same as those of Xemιrus and Priodon. Nipples two, pectoral. Visceral anatomy closely resembling that of Dasypus, the caecum being broad, short, and bifid.

C. truncatus. — The Pichiciago, a small burrowing animal, about 5 inches long, inhabits the sandy plains of the western part of the Argentine Republic, especially the vicinity of Mendoza. Its horny covering is of a pinkish colour, and its silky hair snow white. It is rare, and its habits but little known. A second species, C. retusa, from Bolivia, has been described by Burmeister. It is of rather larger size, and has the dorsal shield attached to the skin of the back, as far as its edge, instead of only along the median line.

Subfamily Dasypodinεe.—Fore feet usually with all five digits developed and with nails, though the first and fifth may be suppressed. The first and second long and slender, with the normal number and relative length of phalanges. The others stout, with short broad metacarpals, and with phalanges greatly reduced in length and generally in number by coalescence. The ungual phalanx of the third very large, that of the others gradually diminishing to the fifth. Dasypus, as now restricted, has the most normal form of manus, but the modifications so markedly developed in all the others (and culminating in Tolypeutes') are foreshadowed, as it were, in it. Ears wide apart. Mamin» one pair, pectoral.

Dasypus.— Teeth 1 ⅛ or f, of which the anterior in the upper jaw is usually implanted in the premaxillary bone. The series of teeth extends posteriorly some distance behind the anterior root of the zygoma, almost level with the hinder edge of the palate. They are large, subcylindrical, slightly compressed, diminishing in size towards each end of the series; the anterior two in the mandible much smaller, and more compressed than the others. Cranial portion of the skull broad and depressed. Facial portion triangular, broad in front and much depressed. Auditory bulla completely ossified, perforated on the inner side by the carotid canal, and continued externally into an elongated bony meatus auditorius, with its aperture directed upwards and backwards. (In all the remaining genera of Dasypodinae the tympanic bone is a mere half ring, loosely attached to the cranium.) Mandible with a high ascending ramus, broad transversely-placed condyle, and high slender coronoid process. Vertebrae: C 7, D 11-12, I. 3, S 8, C 17-18. Head broad and flat above. Muzzle obtusely pointed. Ears of moderate size or rather small, placed laterally, far apart. Body broad and depressed. Carapace with six or seven movable bands between the scapular and pelvic shields. Tail shorter than the body, tapering, covered with plates forming distinct rings near the base. Fore feet with five toes; the first much more slender than the others, and with a smaller ungual phalanx and nail; the second, though the longest, also slender. The third, fourth, and fifth gradually diminishing in length, all armed with very strong, slightly curved, compressed claws, sloping away from an elevated rounded inner border to a sharp, outer, and inferior edge. The hind foot is rather short, with all five toes armed with stout, compressed, slightly curved, obtusely pointed claws,—the third the longest, the second nearly equal to it, the fourth the next, the first and fifth shorter and nearly equal.

To this genus belongs one of the best-known^species of the group, the Six-banded Armadillo or Encoubert (Z>. sexcinctus) of Brazil and Paraguay. A very similar species, D. villosus, the Hairy Armadillo, replaces it south of the Rio Plata. There are also two very small species, D. vellerosus and D. minutus, from the Argentine Republic and North Patagonia. The latter differs from the other three in having no tooth implanted in the premaxillary bone.

Xenurus.— Teeth ⅜ or ⅜, of moderate size and subcylindrical. The most posterior placed a little way behind the anterior root of the zygoma, but far from the hinder margin of the palate. Cranium somewhat elongated, much constricted behind the orbits, and immediately in front of the constriction considerably dilated. Mandible slender; coronoid process very small and sharp-pointed, sometimes obsolete. Vertebrae: C 7, D 12-13, I. 5, S 10, C18. Head broad behind. Ears rather large and rounded, wide apart. Movable bands of carapace 12-13. Tail considerably shorter than the body, and slender, covered with nearly naked skin, with but a few small, scattered, dermal bony plates, chiefly on the under surface and near the apex. On the fore feet the first and second toes are long and slender, with small claws and the normal number of phalanges; the other toes have but two phalanges; the third has an immense falcate claw; the fourth and fifth similar but smaller claws. The hind feet are comparatively small, with five toes, with small, triangular, blunt nails; the third longest, the first shortest. The best known species of this genus, the Tatouay or Cabassou, X. unicinctus, is, after Priodon gigas, the largest of the group. It is found, though not abundantly, in Surinam, Brazil, and Paraguay. Others, X. hispidus and lugubris, have been described, but little is as yet known of them.

Priodon.— Teeth variable in number, and generally differing on the two sides of each jaw, usually from 20 to 25 on each side above and below, so that as many as 100 may be present altogether, but as life advances the anterior teeth fall out, and all traces of their alveoli disappear. The series extends as far back as the hinder edge of the anterior root of the zygoma. They are all very small; in the anterior half of each series they are strongly compressed’ having flat sides and a straight free edge; the posterior teeth are more cylindrical, with flat, truncated, free surfaces. Vertebrae: C7, D 12, L3, S10, C 23. Head small, elongated, conical. Ears moderate, ovate. Carapace with 12-13 movable bands. Tail nearly equal to the body in length, gradually tapering, closely covered with quadrangular scales, arranged in a quincunx pattern. Fore feet with five toes, formed on the same plan as those of Xenurus, but with the claw of the third of still greater size, and that of the others, especially the fifth, proportionately reduced. Hind foot short and rounded, with five very short toes, with short, broad, flat obtuse nails. The only known species, the Great Armadillo (P. gigas), is by far the largest of existing, members of the family, measuring rather more than 3 feet from the tip of the nose to the root of the tail, the tail being about 20 inches long. It inhabits the forests of Surinam and Brazil. The powerful falcate claws of its fore feet enable it to dig with great facility. Its food consists chiefly of termites and other insects, but it is said to attack and uproot newly-made graves for the purpose of devouring the flesh of the bodies contained in them.

Tolypeutes.— Teeth ⅜ or ⅞, rather large in proportion to the size of the skull, the hinder end of the series reaching nearly to the posterior margin of the palate. Vertebrae: C 7, D11, I. 3, S 12,.C 13. Ears placed low on the sides of the head, rather large, broadly ovate. Carapace with its scapular and pelvic shields very free at the sides of the body, forming large chambers into which the limbs can be readily withdrawn. Only three movable bands. Tail short, conical, covered with large bony tubercles. The fore feet formed on the same type as the last, but the peculiarities carried out to a still greater extent. The claw of the third toe is very long and falcate, the first and fifth greatly reduced and sometimes wanting. On the hind foot the three middle toes have broad, flat, subequal nails, forming together a kind of tripartite hoof; the first and fifth much shorter and with more compressed nails.

The Armadillos of this genus have the power of rolling themselves up into a perfect ball, the shield on the top of the head and the tuberculated dorsal surface of the tail exactly fitting into and filling up the apertures left by the notches at either end of the carapace. This appears to be their usual means of defence when frightened or surprised, as they do not burrow like the other species. They run very quickly, with a very peculiar gait, only the tips of the claws of the fore feet touching the ground. Three species are described :— T. tricinctus, the Apar; T. conurus, the Matico; and T. muriei.

Subfamily Tatusiinae.—This contains but one genus, Tatusia. —Teeth f or ∣, very small, subcylindrical. The first and second subcompressed, the last considerably smaller than the others. Theypre-sent the remarkable peculiarity (unique among Edentates, so far as is yet known) of all being, with the exception of the last, preceded by two-rooted milk teeth, which are not changed until the animal has nearly attained its full size. Vertebrae: C 7, D 9-11, I. 5, S 8, C 20-27. Head narrow, with a long,,, narrow, subcylindrical. obliquely-truncated snout. Ears rather large, ovate, and erect, placed close together on the occiput. Carapace with seven to nine distinct movable bands. Body generally elongated and narrow. Tail moderate or long, gradually tapering; its dermal plates forming ve∏r distinct rings for the greater part of its length. Fore feet with four visible toes, and a concealed clawless rudiment of the fifth. Claws all long, slightly curved, and very slender, the third and fourth subequal and alike, the first and fourth much shorter. Hind feet with five toes, all armed with strong, slightly-curved, conical, obtusely pointed nails. The third longest, then the second and fourth; the first and fifth much shorter than the others.

This genus differs from all the other Armadillos in having a pair of inguinal mammae, in addition to the usual pectoral pair, and in producing a large number (four to ten) of young at a birth, all the others having usually but one or two.

The Peba Armadillo, T. septemcincta, is a well-known species, having an extensive range from Texas to Paraguay. It is replaced in the more southern regions of South America by a smaller species, with shorter tail, the Mulita (7 ’. hybrida), so called from the resemblance of its head and ears to those of a mule. T. ka}τpleri is a large species or variety from Surinam.

Fossil remains of Dasypodidae have been found by Lund and others in the caves of Brazil in deposits of Pleistocene age. Some are attributable to existing genera, but others are assigned to distinct modifications of the type called Euryodon, Chlamydotherium, Eιιtatus, &c. In the same region, but still more abundantly in the fluviatile deposits which cover the country in the neighbourhood of Buenos Ayres, are found the remains of one of the most remarkable forms of mammals yet discovered, the Glyptodons, or Hoplophoridae (fig. 39). They differ from the existing Dasypodidae in their large size, and in having the carapace composed of a solid piece (formed by the union of a multitude of bony dermal scutes) without any movable rings, and in having also a ventral piece or plastron. The facial portion of the skull is very short. A long process of the maxillary bone descends from the anterior part of the zygomatic arch. The ascending ramus of the mandible is remarkably high. The teeth are ⅜ in all known species, all much alike, having two deep grooves or flutings on each side, so as to divide them into three nearly distinct lobes (fig. 40). The vertebral column is almost entirely ankylosed into a solid tube, but there is a complex joint at the base of the neck, to allow the head being retracted within the carapace. The limbs are very strong, and the feet short andbroad, resembling externally those of an elephant or tortoise. Many species of the family have been described and figured, especially by Burmeister (in the Annales del Museo publico de Buenos Aires), by whom five genera are recognized, which are thus characterized :— [table]

Family Manidae.

Covered externally (except the under surface of the body and inside of the limbs) with large imbricated horny scales, with scattered hairs growing in the intervals. No teeth. Tongue long, vermiform, and protractile. No accessory articular processes to the lumbar vertebrae, but the anterior zygapophyses largely developed and very concave, completely embracing the semicylindri-cal surfaces of the posterior zygapophyses. Limbs short, with five complete digits on each foot. Scaphoid and lunar bone of carpus united. Uterus bicornuate. Placenta diffused and non-deciduate. The species are mainly terrestrial and fossorial, though one is partially arboreal. All belong to the Ethiopian and Oriental regions of the Old World.

Manis.— Skull somewhat of the form of an elongated cone, with the small end turned forwards; very smooth and free from crests and ridges. No distinction between the orbits and temporal fossa*. The zygomatic arch usually incomplete, owing to the absence of the malar bone. No distinct lacrymal bone. Palate long and narrow. The pterygoids extend backwards as far as the tympanies, but do not meet in the middle line below. Tympanic ankylosed to the surrounding bones, and more or* less bullate, but not produced into a tubular auditory meatus. Kami of mandible very slender and straight, without any angle or coronoid process. From near the anterior extremity of the upper edge a sharp, conical, tooth-like process projects upwards and outwards. No clavicles. No third trochanter to the femur. Ungual phalanges bifid at their terminations. Caudal vertebrae with very long strong transverse processes and numerous chevron bones. Tongue long, vermiform, flattened towards the tip. The retractor or sterno-glossal muscles arise from the hinder extremity of the immensely prolonged ensiform cartilage of the sternum. Stomach with thick, muscular walls and lining membrane, and with a special gland near the middle of the great curvature, consisting of a mass of complex secreting follicles, the ducts of which terminate in a common orifice. No caecum. A gall-bladder. Head small, depressed, narrow, pointed in front, with a very small mouth-opening. Eyes and pinna of ear very small. Body elongated, narrow. Tail more or less elongated, convex above, flat underneath. The whole of the upper surface of the head, the upper surface and sides of the body, the whole of the tail, and the outer sides of the extremities covered with large, overlapping, horny scales, with usually a few stiff hairs growing between and projecting beyond them. The sides and under surface of the head, the under surface of the body, and the inner sides of the limbs without scales but with a rather scanty covering of hair. Limbs short. In walking the dorsal surface and outer sides of the phalanges of the two outer digits of the front feet alone rest on the ground, the points of the nails turning upwards and inwards. The third toe the longest, with a powerful compressed curved claw, the second and fourth with similar but smaller claws, that of the pollex often almost rudimentary. Hind feet plantigrade, with hallux very short, and four other toes subequal, with moderate, curved, subcompressed nails.

The animals of this genus, called Pangolins or Scaly Anteaters, are all of small or moderate size, terrestrial and burrowing, and feed mainly on termites. One small African species climbs trees. They can roll themselves up in a ball when in danger. Their peculiar elongated form, short limbs, long, gradually-tapering tail, and scaly covering give them on a superficial inspection more the appearance of reptiles than of mammals. The species are not numerous, but may be grouped into three sections. (1) Manis proper. Tail considerably exceeding in length both head and body. Scales not covering the dorsal surface of the manus. On fore feet the first toe exceedingly small, but with a distinct short nail; second, fourth, and fifth subequal, with moderate compressed claws; third greatly exceeding the others, with a much larger falcate claw. Two species, both from West Africa: Μ. longicaudata (vertebrae: C 7, D 13, I. 5, S 3, C 46), and Μ. tricuspus (vertebrae: C 7, D 13, I. 6, S 3, C 44). (2) All the others have the scaly covering of the fore limbs extending to the claws, and the tail not exceeding the length of the head and body. On the fore feet the first and fifth toes are equal and very small, the second and fourth equal and longer, the third longest, but not so disproportionately so as in the other section. The tails of most of these are broad at the base and taper towards the extremity. They constitute the genus Pholidotus of Gray, and include Μ. gigantea, West Africa, the largest species of the group, of which the head and body measure 2 feet 6 inches, and the tail the same. Vertebrae: C 7, D 13, I. 6, S 4, C 28. Μ. pentadactyla, Μ. aurita, and M. javanica, all of the Oriental region. (3) One very distinct species, Μ. temminckii, from South and East Africa, with the tail nearly as broad as the body for the whole of its length, and rounded at the end, constitutes the genus Smutsia of Gray.

Family Okycteropodidae.

External surface scantily covered with bristle-like hairs. Teeth numerous, and of peculiar and complex structure, being traversed by a number of parallel vertical pulp-canals. Lumbar vertebrae with no accessory zygapophyses. Femur with a third trochanter. Fore feet without pollex, but all the other digits well developed, with strong moderate-sized nails, suited to digging, the plantar surfaces of which rest on the ground in λvalking. Hind feet with five sαbequal toes. Mouth elongated and tubular. Tongue subvermi-form. Placenta broadly zonular. Feed on animal substances. Terrestrial and fossorial in habits. Limited to the Ethiopian region.

Orycteropus.— The total number of teeth appears to be from •eight to ten in each side of the upper, and eight in the lower jaw; but they are never all in place at one time, as the small anterior teeth are shed before the series is completed behind. In the adult they number usually five on each side above and below, of which the first two are simple and compressed, the next two larger and longitudinally grooved at the sides, the most posterior simple and cylindrical. The structure of all these teeth is quite peculiar among mammals, though resembling that of some fishes. Their summits are rounded before they are worn; their bases do not taper to a root, but are evenly truncated and continually growing. Each tooth is made up of an aggregation of parallel dental systems, having a slender pulp cavity in the centre, from which the dentinal tubes radiate outwards, and being closely packed together each system assumes a polygonal outline as seen in transverse section. No evidence of any vertical succession of teeth has been discovered. Skull moderately elongated. The facial portion sub- •cylindrical and slightly tapering. The zygoma complete and slender. The palate ends posteriorly in the thickened transverse border of the palatines, and is not continued back by the pterygoids. The tympanic is annular, and not ankylosed to the surrounding bones. The mandible is slender anteriorly,, but rises high posteriorly, with a slender recurved coronoid, and an ascending pointed process on the hinder edge below the condyle, which is small, oval, and looks forwards as much as upwards. Vertebrae: C 7, D 13, I. 8, S 6, C 25. The large number of lumbar vertebrae is peculiar among Edentates. Tongue less vermiform than in Myrmecophaga, being thick and fleshy at the base, and gradually tapering to the apex. The salivary apparatus is developed much in the same manner as in that genus, but the duct of the submaxillary gland has no reservoir. The stomach consists of a large subglobular cardiac portion, with a very thick, soft, and corrugated lining membrane, and a smaller muscular, pyloric part, with a comparatively thin and smooth lining. There is a very distinct ileo-caecal valve, and a considerable-sized caecum; also a gall-bladder. No pollex to the fore foot. All the other usual toes well developed, with strong, subcompressed nails, flatter on the hind foot. Head elongated, with a tubular snout, terminal nostrils, and small mouthopening. Ears large, pointed, erect. Tail nearly as long as the body, cylindrical, very thick at the base, tapering to the extremity.

The best known species is the Cape Anteater (0. capcnsis), or “Aard-Vark” (Earth Pig) of the Dutch colonists, from South Africa, an animal not altogether unlike a Pig in size and general appearance. It lives in burrows in the ground, and feeds chiefly on ants and other insects. A second species, or well-marked local varietv, 0. aethiopicus, inhabits the north-eastern parts of Africa.

Extinct Edentata of the Old World.

Certain remains, chiefly of bones of the limbs, found in France and Greece, and assigned to genera called Macotheτium and Ancy-lotherium, united provisionally in the family Macrotheriidae, indicate the existence of animals of large size inhabiting Europe during the Middle Tertiary epoch, the characters of which appear to indicate a generalized Edentate form or something intermediate between the Edentata and Ungulata. In the structure of the phalanges they most resembled the Manidae, but there is some evidence that they possessed teeth. Some fragments from the Eocene of Paris are still more doubtfully assigned by Gervais to the order.

Bibliography of Edenta' a.— No general work on the order has been published but that of Rapp (A nat. Untersuchungen über die Edentaten, 2d ed., 1852), now nearly out of date. Among numerous memoirs on special groups the following may be cited Myrmecophagidιe :—R. Owen, “Anatomy of Great Anteater,” Trans. Zool. Soc., vol. lv.; G. Pouchet, Mém. sur le Grand Fourmilier, 1874,; W. A. Forbes, “Anat. of Great Anteater,” Proc. Zool. Soc., 1882, p. 287. Mega-theriidx ∙R. Owen, Extinct Gigantic S'oth (Mylodon Robustus), 1842; Id., “On the Megatherium,” Philos. Trans., 1851-56; J. Leidy, “Extinct Sloth-tribe of North America,” Smithsonian Contrib. to Knowledge, vii., 1855; ∏. Burmeister, Description de la République Argentine, t iii. Mammifères, 1879,—which contains full references to various memoirs by Owen, Gervais, Reinhardt, and others. Glyptodontidx Owen, Catalogue of Fossil Mammals, Mus. Roy. Coll. Surgeons, 1845; T. H. Huxley, “Osteol. of Glyptodon,” Phil. Trans., 1865; ∏. Burmeister, Annales del Museo Publico de Buenos Ayres, and Descript, de la République Argentine, 1879. Dasypodidx J. Murie, “Anatomy of Tolypeutes." Trans. Linn. Soc., vol. XXX., 1874; A. H. Garrod, Proc. Zool. Soc., 1878. For placentati nof Edentates see W. Turner, Trans. Roy. S∙>c. Edin., xxvii. (1873) p. 72, and Jour. Anat. and Physiol., vols, viii. and x.; A. Milne-Edwards, Ann. Sciences Nat. [6] viii. p. 1; and for brain, P. Gervais, “Formes cérébrales des Edentés,” Nouv. Arch, du Museum, tom. v.; W. Turner, Jour, Anatomy, i. 313 (1867).

Order SIRENIA.

The purely aquatic habits and Fish-like form of the animals of this order caused them to be formerly confounded with the Cetacea, but a more intimate knowledge of their structure has shown that they really belong to a widely different type of the class.

The head is rounded and not disproportionate in size as compared with the trunk, from which it is scarcely separated by any externally visible constriction or neck. Nostrils valvular, separate, and placed above the fora part of the obtuse, truncated muzzle. Eyes very small, with imperfectly formed eyelids, capable, however, of contraction, and with a well-developed nictitating membrane. Ear without any pinna. Mouth of small or moderate size, with tumid lips beset with stiff bristles. General form of the body depressed fusiform. No dorsal fin. Tail flattened and horizontally expanded. Fore limbs paddle-shaped, the digits being enveloped in a common cutaneous covering, though sometimes rudiments of nails are present. No trace of hind limbs. External surface covered with a tough, finely wrinkled, or very rugous skin, naked, or with fine hairs sparsely scattered over it.

The skeleton is remarkable for the massiveness and density of most of the bones of which it is composed, especially the skull and ribs, which must add to the specific gravity of these slow-moving animals, and aid in keeping them to the bottom of the shallow waters in which they dwell, while feeding on aquatic vegetables. The skull presents many peculiarities, among which may be indicated the large size and backward position of the anterior narial aperture, a further modification of that met with in the Tapirs among Ungulates, and presenting some approach to that so characteristic of the Cetacea. The nasal bones are generally absent in the recent forms, or are only found in a most rudimentary condition, attached to the edge of the frontals, far away from the middle line; but in some at least of the extinct species these bones, though small in size, are normal in situation and relations. In very few other respects does the skull present any resemblance to that of the Cetacea. In the spinal column none of the vertebrae are united together to form a sacrum, and the flat ends of the bodies do not ossify separately, so as to form disk-like epiphyses in the young state, as in nearly all other mammals. The anterior caudal vertebrae have well-developed chevron bones. In one genus (Manatus) there are only six cervical vertebrae. There are no clavicles. The humerus has a small but distinct trochlear articulation at the elbow-joint. The two bones of the forearm are about equally developed, and generally ankylosed together at both extremities. The carpus is short and broad, and the digits five in number with moderately elongated and flattened phalanges, which are never increased in number beyond the limit usual in the Mammalia. The pelvis is extremely rudimentary, consisting of a pair of bones suspended at some distance from the vertebral column. In no existing species is there any trace of a hind limb, but in the extinct Halitherium an acetabular depression and rudimentary femur have been discovered.;

Two kinds of teeth, incisors and molars, separated by a wide interval, are generally present. The former may be developed into tusks in the upper jaw, or may be quite rudimentary. The molars vary much in character. In one genus (Rytina) no teeth of any kind are present, at least in the adult. In all, the anterior part of the palate, and a corresponding surface on the prolonged symphysis of the lower jaw, are covered with rough horny plates of peculiar structure, which doubtless assist in mastication. The tongue is small and fixed in position, with a surface resembling that of the plates just spoken of. The salivary glands are largely developed. The stomach is compound, being divided by a valvular constriction into two principal cavities, the first of which is provided with a singular glandular pouch near the cardiac end, and the second usually with a pair of elongated, conical, caecal sacs or diverticula. The intestinal canal is long, and with very muscular walls. There is a caecum, either simple, conical, and with extremely thick walls, as in Halicore, or bifid, as in Manatus. The apex of the heart is deeply cleft between the ventricles. The principal arteries form very extensive and complex retia mirabilia. The lungs are remarkably long and narrow, as, owing to the very oblique position of the diaphragm, the thoracic cavity extends far back over the abdomen. The epiglottis and arytenoid cartilages of the larynx do not form a tubular prolongation as in the Cetacea. The brain is of comparatively small size, and the convolutions "on the surface of the cerebrum few and shallow. The kidneys are simple. Testes abdominal. The uterus is bicornuate. The placenta (in the Dugong) is non-deciduate and diffuse, the villi being scattered generally over the surface of the chorion except at the poles. The umbilical vesicle disappears early. The mammae are two, and pectoral or rather post-axillary in position.

The Sirenia pass their whole life in the water, being denizens of shallow bays, estuaries, lagoons, and large rivers, but unlike the Cetacea are not met with in the high seas, far away from the shore. Their food consists entirely of aquatic plants, either marine algae or freshwater grasses, upon which they browse beneath the surface, as the terrestrial herbivorous mammals do upon the green pastures on shore. They are generally gregarious, slow and inactive in their movements, mild, inoffensive, and apparently unintelligent in disposition. Though occasionally found stranded by the tide or waves, there is no satisfactory evidence that they voluntarily leave the water to bask or feed on the shore. The habit of the Dugong of raising its round head out of water, and carrying its young under the fore fin, seems to have given rise, among the imaginative early voyagers in the Indian Ocean, to the legendary beings, half human and half fish, in allusion to which the name Sirenia was bestowed by liliger on the order, though certainly the face of a Dugong, when closely inspected, does not bear the slightest resemblance to that of the mermaid of romance. The species now existing are very few, and there is reason to believe that the time is not far distant when they will all become extinct. One species, Rhytina stelleri, of the North Pacific, was totally exterminated through the agency of man during the last century; and the others, being valuable for their flesh as food, for their hides, and especially for the oil obtained from the thick layer of fat which lies immediately beneath their skin, rapidly diminish in numbers as civilized populations occupy the regions forming their natural habitat. The surviving species are confined to the tropical regions of the shores of both sides of the Atlantic and the great rivers which empty themselves into that ocean, and to the coasts of the Indian Ocean from the Red Sea to North Australia. In the Miocene and early Pliocene epoch Sirenians abounded in the seas of Europe, and their remains have been found in deposits of corresponding periods of North America. Evidence has also been discovered of the existence of an animal of the group in the seas at the bottom of which the Eocene nummulitic limestone mountain ranges of Egypt were deposited.

The existing genera present such well-marked distinguishing characters that, if they alone were known, they might be placed in separate families; but, as in so many similar cases, our knowledge of the extinct forms, imperfect as it is, goes far to bridge over the distinction between them.

Manatus. — Incisors ⅜, rudimentary, concealed beneath the homy oral plates, and disappearing before maturity. Molars fl, but rarely more than ⅜ present at one time; the anterior teeth falling before the posterior come into use; similar in characters from beginning to end of the series; with square, enamelled crowns, the grinding surface raised into tuberculated transverse ridges. The upper teeth with two ridges and three roots, the lower teeth with an additional (posterior) ridge or talon and two roots. The cervical vertebrae present the remarkable anomaly of being reduced to six in number, the usual vertebral formula being C 6, D 15-18, I. and C 25-29. Rostrum of the skull, formed by the union of the premaxillae in front of the anterior narial aperture, shorter than the length of the aperture and scarcely deflected from the basi-cranial axis. Tail entire, rounded or shovel-shaped. Rudimentary nails on the fore limbs. Caecum bifid. Habitat the shores of, and the great rivers which empty themselves into, the Atlantic within the tropics. The American and African forms are generally considered to be distinct species (J∕. aιιstralis and Μ. senegalensis), though they differ but little from each other in anatomical characters and in habits. They are rather fluviatile than marine, ascending large rivers almost to their sources. See Manatee. Halicore.— In the upper jaw a pair of large, nearly straight, tusklike incisors, directed downwards and forwards, partially coated with enamel. In the male they have persistent pulps, and bevelled cutting edges, which project a short distance from the mouth, but in the female, though they remain through life in the alveolar cavity, they are not exserted, and, the pulp cavity being filled with osteodentine, they soon cease to grow (as in the female Narwhal). In the young there is also a second small deciduous incisor on each side above. At this age there are also beneath the horny plate which covers the anterior portion of the mandible four pairs of slender conical teeth lodged in wide alveolar depressions. These become absorbed before the animal reaches maturity. The molars are usually ⅜, sometimes ∣, altogether, but not all in place at once, as the first falls before the last rises above the gum; they are more or less cylindrical in section, except the last, which is compressed and grooved laterally, without distinction into crown and Toot, increasing in size from before backwards, with persistent pulps and no enamel. The summits of the crowns are tuberculated before wearing, afterwards flattened or slightly concave. Skull with rostrum formed by the union of the premaxillae in front of the narial aperture, longer than the aperture itself, bending downwards at a right angle with the basi-cranial axis, and enclosing the sockets of the large incisor tusks. Anterior part of the lower jaw bent down in a corresponding manner. Vertebrae: C7, D18-19, I. and C 30. Tail broadly notched in the middle line, and with two pointed lateral lobes. No nails on the fore limbs. Caecum single.

The Dugongs are more distinctly marine in their habits than the Manatees, feeding chiefly on sea-water algae. They inhabit the shallow bays and creeks of the Red Sea, east coast of Africa, Ceylon, islands of the Bay of Bengal and the Indo-Malayan Archipelago (including the Philippines), and the north coast of Australia, ranging from Barrow Reefs on the west to Moreton Bay on the east. Though the distinctive characters are not very obvious, they have been divided into three species, according to the localities which they respectively inhabit :— H. tabernaculi from the Red Sea, H. dugong from the Indian seas, and H. australis from Australia. The last-named has lately been the object of a regular “fishery,” chiefly on account of its oil, which is peculiarly clear, limpid, and free from disagreeable smell, and is said to have the same medical properties as cod-liver oil. Although often stated in books to attain the length of 20 feet when adult, there does not appear to be any evidence from actual specimens in museums that Dugongs ever reach half that size, 8 feet being the common length of adult animals.

Rhytina.— No teeth, their place being supplied functionally by the dense, strongly-ridged, horny oral plates. Premaxillary rostrum about as long as the anterior narial aperture, and moderately deflected. Vertebrae: C 7, D 19, I. and C 34-37. Head very small in proportion to the body. Tail with two lateral pointed lobes. Pectoral limbs small and truncated. Skin naked and covered with a very thick, hard, rugged bark-like epidermis. Stomach without civcal appendages to the pyloric cavity. Caecum simple.

Only one species of this genus is known, R. stelleri, the Northern Sea-cow, by far the largest animal of the order, attaining the length of 20 to 25 feet. It was formerly an inhabitant of the shores of two small islands in the North Pacific, Behring’s and the adjacent Copper Island, on the former of which it was discovered by the ill-fated navigator whose name the island bears, when, with his accomplished companion, the German naturalist Steller, he was wrecked upon it in 1741. Twenty-seven years afterwards (1768), as is commonly supposed, the last of the race was killed, and its very existence would have been unknown to science but for the interesting account of its anatomy and habits left by Steller, and the few more or less perfect skeletons which have recently rewarded the researches carried on in the frozen soil of the islands around which it dwelt. There is no evidence at present of its having inhabited any other coasts than those of the islands just named, though it can hardly be supposed that its range was always so restricted. When first discovered it was extremely numerous in the shallow bays round Behring’s Island, finding abundant nutriment in the large laminariae growing in the sea. Its extirpation is entirely due to the Russian hunters and traders who followed upon the track of the explorers, and who, upon Steller’s suggestion, lived upon the flesh of the great Sea-cows. Its restricted distribution, large size, inactive habits, fearlessness of man, and even its affectionate disposition towards its own kind when wounded or in distress, all contributed to accelerate its final extinction.

Extinct Sirenia.

The Miocene and early Pliocene seas of Europe abounded in Sirenians, to which the generic name of Halitherium was given by Kaup. They had large tusk-like incisors in the upper jaw, as in the existing Dugongs, though not so greatly developed. Their molar teeth were ⅛ or ⅞, anteriorly simple and single-rooted, posteriorly those above with three and those below with two roots, and with enamelled and tuberculated or ridged crowns, in all which respects they more resemble those of the Manatee than of the Dugong. The anterior molars were deciduous. Some species at least had nasal bones, short, broad, but normal in position, whereas in all the existing genera these bones are quite rudimentary. Another and still more important evidence of conformity to the general mammalian type is the better development of the pelvic bone, and the presence of a small styliform femur articulated to the acetabulum, although no traces of any other part of the limb have been discovered. These ancient Sirenians were thus, in dental, cranial, and other osteological characters, less specialized than are either of the existing species, and, if the intermediate links could be discovered, might well be looked upon as ancestral forms from which the latter have been derived, but at present the transitional conditions have not been detected. So far as is yet known, when changes in the physical conditions of the European seas rendered them unfitted to be the habitation of Sirenians, the Halitherium type still prevailed. If the existing Dugongs and Manatees are descended from it, their evolution must have taken place during the Pliocene and Pleistocene epochs, the one in seas to the east, the other to the west of the African continent, which has long formed a barrier to their intercommunication. Halitherium remains have been found in many parts of Germany, especially near Darmstadt, also in France, Italy, Belgium, Malta, the isthmus of Suez, &c. Until lately none were known from England, probably owing to the absence of beds of an age corresponding to those in which they are found on the European continent; but recently a skull and several teeth have been detected among the rolled debris of Miocene formations, out of which the Red Crag of Suffolk is partially composed. The species are not yet satisfactorily characterized. Some of them appear to have attained a larger size than the existing Manatee or Dugong. One of these from the Pliocene of Italy and France, having but ⅛ molar teeth, has been separated generically under the name of Felsinotherium by Capellini, by whom it has been fully described. A portion of a skull found in Belgium has been named Crassitherium by Van Beneden; and some compressed teeth, somewhat similar to but larger than those of the Dugong, discovered in the department of Lot-et-Garonne, France, gave origin to the genus Rytiodus of E. Lartet. Of this more complete remains have recently been described by Delfortrie. The rostrum is more elongated than in Halitherium, but the skull is otherwise very similar, as are the molar teeth. The incisors are very large, exserted, strongly compressed, almost sabre-like, rounded on the upper or anterior surface, sharp below, concave on the external and convex on the inner side, and transversely striated.

Pachyacanthus of Brandt, from the Vienna basin, is also, according to Van Beneden, another form of Sirenia, of which, however, the skull is not known. In various Miocene and perhaps Eocene marine formations of the United States of America remains of Sirenians have been found, but mostly in such a fragmentary condition that they afford at present little evidence of the early history of the group in that country. A more satisfactory discovery is that of a nearly complete skull and some bones from a limestone Tertiary formation in Jamaica. It is of smaller size than the Manatee, and as far as the teeth are concerned, of a still more generalized character than Halitherium, the dentition being apparently i ⅜, c ⅜, p ⅜, wι∣=48. The incisors are small, not developed into tusks; thé canines (wanting in all existing Sirenians) are rather larger than the incisors, judging by the sockets; and the molars are bilophodont, and covered with enamel. It has been described by Professor Owen under the name of Prorastomus sirenoides. Unfortunately we have no knowledge of the geological antiquity of the formation in which it was embedded. Lastly must be mentioned the Eothcrium egyptiacum, Owen, founded on the cast of a brain, with a small quantity of surrounding bone, discovered in the nummulitic limestone of Eocene age of the Mokattam Hills, near Cairo. The brain is narrower than in Manatus, and resembles that of Halitherium. This is of interest as the most ancient known evidence of any Sirenian whose age has been geologically determined.

The few facts as yet collected relating to the former history of the Sirenia leave us as much in the dark as to the origin and affinities of this peculiar group of animals as we were when we only knew the living members. They lend no countenance to their association with the Cetacea, and on the other hand their supposed affinity with the Ungulata, so much favoured by modem zoologists, receives no very material support from them.

Bibliography of Sirenia. — J. F. Brandt, Symbolic Sirenologicae, St Petersburg, 3 fasciculi, 1846-61-68,—an exhaustive account of the anatomy, affinities, and literature of the group, with copious illustrations of the osteology of Blιytina. Anatomy of Dugong Everard Home, Phil. Trans., 1820, p. 315; Owen, Proc. Zool. Soc., 1838, p. 29. Manatee Vrolik, Bijdr. tot de Dierkunde, 1851; Murie, Trans. Zool. Soc. Land., vol. viii. p. 127, 1870, and vol. xi. p. 19, 1880; Garrod, ibid., vol. X. p. 137, 1875. *Extinct Sirenia Gervais, Journal de Zoologie, tom. i. p. 332, 1872.

Order CETACEA.

This is perhaps the most distinctly circumscribed and natural of all the larger groups into which the class is divided.

The external form is Fish-like, the body being fusiform, passing anteriorly into the head without any distinct constriction or neck, and posteriorly tapering off gradually towards the extremity of the tail, which is provided with a pair of lateral, pointed expansions of skin supported by dense fibrous tissue, called “flukes,” forming together a horizontally placed triangular propelling organ, notched in the middle line behind.

The head is generally large, in some species attaining to even more than one-third of the entire length of the animal, and the aperture of the mouth is always wide, and bounded by stiff immobile lips. The fore limbs are reduced to the condition of flattened ovoid paddles, encased in a continuous integument, showing no external sign of division into fore arm and manus, or of separate digits, and without any trace of nails. There are no sigμs of hind limbs visible externally. The general surface of the skin is smooth and glistening, and devoid of hair, although in many species there are a few fine bristles in the neighbourhood of the mouth, which may persist through life or be present only in the young state. Immediately beneath the skin, and intimately connected with it, is a thick layer of fat, held together by a dense mesh of areolar tissue, constituting the « blubber,” which serves the purpose of the hairy covering of other mammals in retaining the heat of the body. In nearly all species a compressed median dorsal tegumentary fin is present. The eye is small, and is not provided with a nictitating membrane or true lacrymal apparatus. The external auditory meatus is a very minute aperture in the skin situated at a short distance behind the eye, and there is no vestige of a pinna. The nostrils open separately or by a single crescentic valvular aperture, not at the extremity of the snout, but near the vertex.

The bones generally are spongy in texture, the cavities being filled with oil. In the vertebral column, the cervical region is remarkably short and immobile, and the vertebrae, originally always seven in number, are in many species more or less fused together into a solid mass. The odontoid process of the axis, when that bone is free, is usually very obtuse, or even obsolete. None of the vertebrae are united together to form a sacrum. The lumbar and caudal vertebrae are numerous and large, and, as their arches are not connected by any articular processes (zygapophyses), they are capable of a very free motion in all directions. The epiphyses at the ends of the vertebral bodies are very distinct flattened disks, not uniting until after the animal has attained its full dimensions. There are largely developed chevron bones, the presence of which indicates the distinction between the caudal and lumbar vertebrae.

The skull is modified in a very peculiar manner. The brain-case is short, broad, and high, almost spherical in fact. The supra-occipital bone rises upwards and forwards from the foramen magnum, to meet the frontale at the vertex, completely excluding the parietals from the upper region of the cranium. The frontale are expanded laterally to form the roof of the orbits. The anterior narial aperture opens upwards, and has in front of it a more or less horizontally prolonged rostrum, formed of the maxillae, premaxillae, vomer, and mesethmoid cartilage, extending forwards to form the upper jaw or roof of the mouth.

There are no clavicles. The humerus is freely movable on the scapula at the shoulder-joint, but beyond this the articulations of the limb are imperfect, flattened ends of the bones coming in contact with each other, with fibrous tissue interposed, allowing of scarcely any motion. The radius and ulna are distinct, and about equally developed, and much flattened, as are all the bones of the manus. There are four, or more commonly five, digits, and the number of the phalanges of the second and third digits always exceeds the normal number in mammals, sometimes very considerably; they present the exceptional character of having epiphyses at both ends. The pelvis is represented by a pair of small styliform bones placed longitu dinally, suspended below and at some distance from the vertebral column at the commencement of the caudal region. These appear to represent the ischia, as the crura of the corpora cavernosa are attached to them. In some species, to the outer surface of these are fixed other small bones or cartilages, the rudiments of the hind limb.

Teeth are generally present, but exceedingly variable in number. In the existing species, they are of simple, uniform character, all having conical or compressed crowns and single roots, and are never preceded by milk teeth. They are therefore homodont and monophyodont. In one group, the Mystacocetes, the teeth are absent (except in the foetal condition), and the palate is provided with numerous transversely placed horny laminae or “baleen.” The salivary glands are rudimentary or absent. The stomach is multilocular. The intestinal canal simple, and only in some species provided with a small caecum. The liver is very little fissured, and there is no gall-bladder. The vascular system is greatly complicated by arterial and venous plexuses, or retia mirabilia. The larynx is of peculiar shape, the arytenoid cartilages and the epiglottis being much elongated, and together forming a tubular prolongation, which projects into the posterior nares, and when embraced by the soft palate forms a continuous passage between the nostrils and the trachea, as in the Ungulates, but in a more perfect manner. The brain is large relatively to the size of the animal, very round in form, and with its surface divided by sulci into very numerous and complex convolutions. The kidneys are deeply lobulated. The testes are abdominal. There are no vesiculae seminales, nor os penis. The uterus is bicornuate, the placenta non-deciduate and diffuse. The mammae are two in number, and the nipples placed in depressions on each side of the vulva. The principal ducts of the gland are dilated during lactation into large reservoirs, into which the milk collects, and from which it is injected by the action of a compressor muscle into the mouth of the young animal, by which means the process of sucking under water is greatly facilitated and expedited.

The animals of the order Cetacea abound in all known seas, and some species are inhabitants of the larger rivers of South America and Asia. Their organization necessitates their passing their life entirely in the water, as on land they are absolutely helpless. They have, however, to rise very frequently to the surface for the purpose of respiration; and, in relation to the constant upward and downward movement in the water thus necessitated, their principal instrument of motion, the tail, is expanded horizontally, quite unlike that of a Fish, whose movements are mainly in straightforward or lateral directions. The position of the respiratory orifice or nostril on the highest part of the head is very important for this mode of life, as it is the only part of the body the exposure of which above the surface is absolutely necessary. Of the numerous erroneous ideas connected with natural history, few are so widespread and still so firmly believed, notwithstanding repeated expositions of its falsity, as that the Cetacea spout out through their blowholes water taken in at the mouth. The fact is, the “spouting,” or more properly “blowing,” of the Whale is nothing more than the ordinary act of expiration, which, taking place at longer intervals than inland animals, is performed with a greater amount of emphasis. The moment the animal rises to the surface it forcibly expels from its lungs the air taken in at the last inspiration, which of course is highly charged with watery vapour in consequence of the natural respiratory changes. This, rapidly condensing in the cold atmosphere in which the phenomenon is generally observed, forms a column of steam or spray, which has been erroneously taken for water. It also often happens, especially when the surface Of the ocean is agitated into waves, that the animal commences its expiratory puff before the orifice has quite cleared the top of the water, some of which may thus be driven upwards with the blast, tending to complete the illusion. In hunting Whales the harpoon often pierces the lungs or air passages of the unfortunate victim, and then fountains of blood may be forced high in the air through the blowholes, as commonly depicted in scenes of Arctic adventure; but this is nothing more (allowance being made for the Whale’s peculiar mode of breathing) than what always follows severe wounds of the respiratory organs of other mammals.

All the Cetacea are predaceous, subsisting on living animal food of some kind. One genus alone (Orca) eats other warm-blooded animals, as seals, and even members of its own order, both large and small. Many feed on fish, others on small floating crustaceans, pteropods, and medusae, while the principal staple of the food of many is constituted by the various species of cephalopods, Loligo and other Teuthidae, which must abound in some seas in vast numbers, as they form almost the entire support of some of the largest members of the order. In size the Cetacea vary much, some of the smaller Dolphins scarcely exceeding 4 feet in length, while others are the most colossal of all animals. It is true that most statements of their bulk found in general and even zoological literature are greatly exaggerated, but even when reduced to their actual dimensions (which will be mentioned under the respective genera) some of the existing Whales exceed in size that of any animal living either at present or in former times of which we have any certain evidence. With some exceptions, the Cetacea generally are timid inoffensive animals, active in their movements, and very affectionate in their disposition towards one another, especially the mother towards the young, of which there is usually but one, or at most two, at a time. They are generally gregarious, swimming in herds or “schools” (so termed by the whalers) sometimes amounting to many thousands in number; though some species have hitherto only been met with either singly or in pairs.

Relations of the different Cetacea to each other and to other Mammals.— As before said, the Cetacea form a perfectly well-defined group, sharply separated from all other mammals, and with no outlying or doubtful forms at present known. Among the existing members of the order, there are two very distinct types, the Toothed Whales or Odontoceti and the Baleen Whales or Mystacoceti, which present as many marked distinguishing structural characters as are found between many other divisions of the Mammalia which are reckoned as orders. The extinct Zeuglodon, so far as its characters are known, does not fall into either of these groups, but is in some respects an annectant form, and therefore must be placed, provisionally at least, in a third group by itself.

The Mystacocetes appear at first sight to be the most specialized and aberrant of the existing Cetacea, as indicated by the absence of teeth, the presence of baleen, and the form and size of the mouth; but, as we see in other groups, dental characters, and all such as relate to the prehension of food generally, are essentially adaptive and consequently plastic or prone to variation, and hence cannot well be relied upon as tests of affinity. In another character, also adaptive, the laxity of the connexion of the ribs with the vertebral column and with the sternum, and the reduction of that bone in size, allowing great freedom of expansion of the thoracic cavity for prolonged immersion beneath the water, the Mystacocetes have passed beyond the Odontocetes in specialization. On the other hand, the greater symmetry of the skull, the more anterior position of the external nostrils and their double external orifice, the form of the nasal bones, the presence of a distinctly developed olfactory organ, the mode of attachment of the periotic bone to the cranium, the presence of a caecum and the regular arrangement of the alimentary canal, the more normal characters of the manus and the better development of the muscles attached to it, and the presence, in many species at least, of parts representing not only the bones but the muscles and ligaments of a hind limb, all show less deviation from the ordinary mammalian type than is presented by the Odontocetes. Taking all these characters into consideration, it does not appear reasonable to suppose that either type has been derived from the other, at all events in the form in which we see it now, but rather that they are parallel groups, both modified in different fashions from common ancestors.

Among the Mystacocetes, in the especially distinguishing characters of the division, the Balaenopterae are less specialized than the Balaenae, which in the greater size of the head, the length and compression of the rostrum, the development of the baleen, and shortness of the cervical region are exaggerated forms of the type, and yet they retain more fully some primitive characters, as the better development of the hind limb, the pentadactylous manus, and the absence ofc a dorsal fin. Both forms are found distinct in a fossil state as far back as the early Pliocene age, but generally represented by smaller species than those now existing. The Mystacocetes of the Miocene seas were, so far as we know at present, only Balaenopterae, some of which (Cetotherium) were, in the elongated flattened form of the nasal bones, the greater distance between the occipital and frontal bone at the top of the head, and the greater length of the cervical vertebrae, more generalized than those now existing. In the shape of the mandible also, Van Beneden, to whose researches we are chiefly indebted for a knowledge of these forms, discerns some approximation to the Odontocetes.

Among the last-named group there are several distinct types, of which that represented by Platanista, although in some respects singularly modified, has been considered to present on the whole approximations towards the more normal and general type of mammalian structure. It is therefore interesting to find a similar form well represented among the earliest fossil remains of Cetaceans in Europe. Almost all the other members of the suborder range themselves under the two principal heads of Ziphioids (or Physeteroids) and Delphinoids. The former is an ancient and once abounding type, of which the Sperm Whale (Physeter) is a highly specialized form. Among the latter, Globicep>halus is a modified form as regards the structure of its anterior extremity, and Monodon as regards its dentition, while I)elphinus with its various minor subdivisions may be regarded as the dominating type of Cetaceans at the present day, abundant in slightly differentiated species and abundant in individuals. They are in this respect to the rest of the order much as the hollow-horned Ruminants are to the Ungulates.

The earliest Cetaceans of whose organization we have anything like complete evidence are the Zeuglodons of the Eocene period, which approach in the structure of skull and teeth to a more generalized mammalian type than either of the existing suborders. The smallness of the cerebral cavity compared with the jaws and the rest of the skull they share with the primitive forms of many other types. The forward position of the narial aperture and the length and flatness of the nasal bones, which distinguish them from all existing forms, we must also suppose to be a character at one time common to all Cetaceans, though now retained (but to a less degree) only by the Mystacocetes. Even Squalodon i which in its heterodont dentition so much resembles Zeuglodon as to have been placed by some zoologists in the same genus, entirely differs from it, and conforms with the ordinary Dolphins in its essential cranial characters.

The origin of the Cetacea is at present involved in much obscurity. They present no signs of closer affinity to any of the lower classes of vertebrates than do many other members of their own class. Indeed in all that essentially distinguishes a mammal from the oviparous vertebrates, whether in the osseous, nervous, reproductive, or any other system, they are as truly mammalian as any other group. Any supposed marks of inferiority, as absence of limb structure, of hairy covering, of lacrymal apparatus, &c., are obviously modifications (or degradations, as they may be termed) in adaptation to their special mode of life. The characters of the teeth of Zeuglodon and other extinct forms, and also, of the foetal Mystacocetes, clearly indicate that they have been derived from mammals in which the heterodont type of dentition was fully established. The steps by which a land mammal may have been modified into a purely aquatic one are clearly indicated by the stages which still survive among the Carnivora, in the Otariεe, and in the true Seals. A further change in the same direction would produce an animal somewhat resembling a Dolphin, and it has been thought that this may have been the route by which the Cetacean form has been developed. There are, however, great difficulties in the way of this view. If the hind limbs had ever been developed into the very efficient aquatic propelling organs they present in the Seals, it is not easy to imagine how they could have become completely atrophied and their function transferred to the tail. It is more likely that the Whales were derived from animals with long tails, which were used in swimming, eventually with such effect that the hind limbs became no longer necessary. The powerful tail, with its lateral cutaneous flanges, of an American species of Otter (Pteronura sandbaclιiι) may give an idea of this member in the primitive Cetaceans. But the structure of the Cetacea is, in so many essential characters, so unlike that of the Carnivora that the probabilities are against these orders being nearly related. Even in the skull of the Zeuglodon, which has been cited as presenting a great resemblance to that of a Seal, quite as many likenesses may be traced to one of the primitive Pig-like Ungulates (except in the purely adaptive character of the form of the teeth), while the elongated larynx, complex stomach, simple liver, reproductive organs both male and female, and foetal membranes of the existing Cetacea are far more like those of that group than of the Carnivora. Indeed it appears probable that the old popular idea which affixed the name of “Sea-Hog” to the Porpoise contains a larger element of truth than the speculations of many accomplished zoologists of modern times. The fact that Platanista, which, as mentioned above, appears to retain more of the primitive characteristics of the group than any other existing form, and also the somewhat related Inia from South America, are both to the present day exclusively fluviatile, may point to the freshwater origin of the whole group, in which case their otherwise rather inexplicable absence from the seas of the Cretaceous period would be accounted for.

Suborder MYSTACOCETI, the Balaenoidea, or Whalebone Whales.

Teeth never functionally developed, but always disappearing before the close of intra-uterine life. Palate provided with plates-of baleen or “whalebone." Skull symmetrical. Nasal bones forming a roof to the anterior nasal passages, which are directed upwards and forwards. Maxilla produced in front of, but not over, the orbital process of the frontal. Lacrymal bones small and distinct from the jugal. Tympanic bone ankylosed with the periotic, which is attached to the base of the cranium by two strong diverging processes. Olfactory organ distinctly developed. Rami of mandible arched outwards, their anterior ends meeting at air angle, and connected by fibrous tissue without any true symphysis. All the ribs at their upper extremity articulating only with the transverse processes of the vertebrae; their capitular processes, when present not articulating directly with the bodies of the vertebrae. Sternum composed of a single piece, and articulating only with a single pair of ribs. No ossified sternal ribs. External openings of nostrils distinct from each other, longitudinal. A short conical caecum.

These animals have, when in the foetal state, numerous, minute, calcified teeth lying in the dental groove of both upper and lower jaws. They are best developed about the middle of foetal life, after which period they are absorbed, and no trace of them remains at the time of birth. The baleen or whalebone does not make its appearance until after birth. It consists of a series of flattened horny plates, between three and four hundred in number, on each side of the palate, with a bare interval along the middle line. They are placed transversely to the long axis of the palate, with very short intervals between them. Each plate or blade is somewhat triangular in form, with the base attached to the palate and the apex hanging downwards. The outer edge of the blade is hard and smooth, but the inner edge and apex fray out into long bristly fibres, so that the roof of the whale’s mouth looks as if covered with hair, as described by Aristotle. At the inner edge of each principal blade are two or three much smaller or subsidiary blades. The principal blades are longest near the middle of the series, and gradually diminish towards the front and back of the mouth. The horny plates grow from a dense fibrous and highly vascular matrix, which covers the palatal surface of the maxillae, and which sends out lamellar processes, one of which penetrates the base of each blade. Moreover, the free edge of these processes is covered with very long vascular thread-like papillae, one of which forms the central axis of each of the hair-like epidermic fibres of which the blade is mainly composed. A tranverse section of fresh whalebone shows that it is made up of numbers of these soft vascular papillae, circular in outline, each surrounded by concentrically arranged epidermic cells, the whole bound together by other epidermic cells, that constitute the smooth cortical (so-called “enamel") surface of the blade, which, disintegrating at the free edge, allows the individual fibres to become loose and assume the hair-like appearance before spoken of. These fibres differ from hairs in not being formed in depressed follicles in the enderon, but rather resemble the fibres composing the horn of the Rhinoceros. The whalebone in fact consists of nothing more than modified papillae of the buccal mucous membrane, with an excessive and cornified epithelial development. The blades are supported, and bound together for a certain distance from their base, by a mass of less hardened epithelium, secreted by the surface of the palatal membrane or matrix of the whalebone in the intervals of the lamellar processes. This is the “intermediate substance” of Hunter, the “gum” of the whalers. Baleen varies much in colour in different species. In some it is almost jet black, in others slate colour, horn colour, yellow, or even creamy-white. In some the blades are variegated with longitudinal stripes of different hues. It differs also greatly in other respects, being short, thick, coarse, and stiff in some, and greatly elongated and highly elastic in those species in which it has attained its fullest development. Its function is to strain the water from the small marine molluscs, crustaceans, or fish upon which the whales subsist. In feeding they fill the immense mouth with water containing shoals of these small creatures, and then, on their closing the jaws and raising the tongue, so as to diminish the cavity of the mouth, the water streams out through the narrow intervals between the hairy fringe of the whalebone blades, and escapes through the lips, leaving the living prey to be swallowed.

Our knowledge of the different structural modifications attained by members of this important group of mammals, though largely increased of late years, is still imperfect. Formerly they were all divided into Right Whales {Balaena) and Rorquals or Finwhales (Balaenoptera), the latter distinguished by their smaller heads, elongated and slender form, free cervical vertebrae, tetradactylous manus, and the presence of very conspicuous longitudinal furrows or folds in the skin of the throat and chest, and of a small adipose dorsal fin. Recent discoveries have, however, brought to light several forms holding a somewhat intermediate position, and presenting combinations of characters not found in either of the larger known sections. According to our present knowledge the group is naturally divided into five very distinct genera. As these will be more fully described in the article Whale, it will be sufficient at present to indicate their principal characteristics.

Balaena. — Skin of throat smooth, not furrowed. No dorsal fin. Cervical vertebrae united into a single mass. Pectoral limb short, broad, and pentadactylous. Head very large. Baleen very long and narrow, highly elastic and black. Scapula high, with a distinct coracoid and coronoid process. This genus contains the well-known Greenland Right Whale {B. mysticetus) of the Arctic seas, the whalebone and oil of which are so much valued in commerce, and also other whales, distinguished from this by having heads somewhat smaller in proportion to the body, with shorter baleen, and a larger number of vertebrae. These inhabit the temperate seas of both northern and southern hemispheres, and have been divided by zoologists into several species in accordance with their geographical distribution,— B. biscayensis of the North Atlantic, B. japonica of the North Pacific, B. australis of the South Atlantic, and B. antipodarum and novae-zelandiae of the South Pacific; but the differential characters by which they have been separated—external as well as anatomical—are so slight and so liable to individual variation that it is not improbable that when they are better known they will all come to be regarded as forming but a single species.

iVeobalaena. — Known chiefly at present by the characters of the skeleton and baleen, which are very different from those of all other whales, but said to combine absence of plications of the throat with the presence of a dorsal fin. The cervical vertebrae are united. The manus small, narrow, and tetradactylous, wanting the pollex. The ribs remarkably expanded and flattened. The scapula very low and broad, with completely developed acromion and coracoid processes. Baleen very long, slender, elastic, and white. A single at present very rare species, A r . marginata, from the Australian and New Zealand seas, is the smallest of the Whalebone Whales, being not more than 20 feet in length.

Rachianectes.— This combines the small head, elongated form, and narrow pectoral fin of Balaenoptera with the smooth skin of the throat and absence of the dorsal fin of Balaena. The baleen is the shortest and coarsest of any of the group. Its osteology is imperfectly known. One species, R. glaucus, the Grey Whale of the North Pacific.

Megaptera.— Head of moderate size. Baleen plates short and broad. Cervical vertebrae free. Scapula with acromion and coracoid process absent or rudimentary. Skin of throat plicated. Dorsal fin low. Pectoral limb tetradactylous, very long and narrow, attaining about one-fourth of the length of the entire animal, the metacarpus and phalanges being greatly developed, and the latter very numerous. Animals of this genus, called “Humpbacks” by the whalers, are found in almost all seas. They have been divided into many species, but no satisfactory characters have yet been pointed out by which these can be distinguished from one another.

Balaenoptera. — Head small and flat, and pointed in front. Body long and slender. Skin of throat plicated. A small falcate dorsal fin. Baleen short and coarse. Cervical vertebrae free. Scapula low and broad, with a large acromion and coracoid process. Pectoral limb tetradactylous, small, narrow, and pointed. This genus contains the various species of Rorquals, Fin-whales, Fin-backs, Finners, or Razor-backs, as they are variously called, some of which are found in almost every sea. Among them are the most gigantic of all animals, B. sibbaldii, which attains the length of 80 feet, and the small B. rostrata, which does not exceed 30. There are certainly four quite distinct modifications of this genus, represented by the two just mentioned, and by B. musculus and B. borealis, all inhabitants of British seas, but the question whether almost identical forms found in the Southern and Pacific Oceans are to be regarded as specifically identical or as distinct awaits the result of future researches.

Suborder ARCHAeOCETI.

This group is formed to include certain extinct Cetaceans, which are at present only known by more or less fragmentary portions of their skeleton and teeth, and whose position and affinities are therefore still subject to doubt.

In the anterior part of both jaws the teeth are simple, conical, or slightly compressed, and sharp-pointed. The first three in the upper jaw are distinctly implanted in the premaxillary bone, and so may be reckoned as incisors. The tooth which succeeds, or the canine, is also simple and conical, but it does not exceed the others in size. This is followed by five teeth with two distinct roots, and' compressed, pointed crowns, with denticulated cutting edges. The dentition is therefore i ⅜, c ⅜, p and m ⅞ = 36, resembling that of some Seals. General form of the skull elongated and much depressed. Brain cavity very small, and the sku∏ between it and the orbits elongated and narrow. Temporal fossae very large. A strong sagittal crest. Rostrum long and narrow, differing from that of other Cetaceans in the large extent to which the premaxillae form the sides of the anterior extremity. Nasal bones elongated, flat, and narrow, the opening of the anterior nares being over the middle of the elongated compressed rostrum. All the cervical vertebrae free. The characters of the dorsal vertebrae, and mode of articulation of the ribs, appear to have resembled those of Platanista rather than Balaena, Physeter, or Delphinus. Lumbar vertebrae with elongated bodies. Characters of the limbs not known with certainty.

All the known fossil remains belonging to the animals of this group may be referred, provisionally at least, to the genus Zeuglodon, so named because the first section of a molar tooth examined was taken from the base of the crown, where it was beginning to divide into the two roots, and looked like two single teeth “linked or yoked together.” This name was substituted by Owen for the earlier one Basilosaurus of Harlan, with the consent of that author, on the mammalian nature of the animal being demonstrated. The latter name is, however, still generally retained by American zoologists. The remains have hitherto been found chiefly in the Eocene formations of the States of Alabama, Louisiana, Mississippi, and Arkansas, and have been assigned to several species. A portion of a skull is recorded from the Barton Clay (Eocene) of Hampshire, England.

Suborder 0D0NT0CETI, the Delphinoidea, or Toothed Whales.

Calcified teeth always present after birth; generally numerous,, but sometimes a very limited number (in a few cases none) are functionally developed. No baleen. Upper surface of the skull more or less asymmetrical. Nasal bones in the form of nodules or flattened plates, applied closely to the frontale, and not forming any part of the roof to the narial passage, which is directed upwards and backwards. Olfactory organ rudimentary or absent. Hinder end of the maxilla expanded and covering the greater part of the orbital plate of the frontal bone. Lacrymal bone either inseparable from the jugal, or, when distinct, very large, and forming part of the roof of the orbit. Tympanic bone not ankylosed with the periotic, which is usually only attached to the rest of the skull by ligament. Rami of mandible nearly straight, much expanded in height posteriorly, with a wide funnel-shaped aperture to the dental canal, and coming in contact in front by a flat surface of variable length, but always constituting a true symphysis. Several of the anterior ribs with well-developed capitular processes, which articulate with the bodies of the vertebrae. Sternum almost always composed of several pieces, placed one behind the other, with which several pairs of ribs are always connected by the intervention of well-developed cartilaginous or ossified sternal ribs. External respiratory aperture single, the two nostrils uniting before they reach the surface, usually in the form of a transverse subcrescentic valvular aperture, situated on the top of the head. Manus always pentadactylous, though the first and fifth digits are usually very little developed. No caecum, except in Platanista. Family Physeteridae.

No functional teeth in the upper jaw. Mandibular teeth various, often much reduced in number. Bones of the cranium raised so as to form an elevated prominence or crest behind the nares. Pterygoid bones thick, produced backwards, meeting in the middle line, and not involuted to form the outer wall of the post-palatine air-sinuses, but simply hollowed on their outer side. Transverse processes of the arches of the dorsal vertebrae, to which the tubercles of the ribs are attached, ceasing abruptly near the end of the series, and replaced by processes on the body at a much lower level, and not on a line, or serially homologous with them, but serially homologous anteriorly with the heads of the ribs, and posteriorly with the transverse processes of the lumbar vertebrae. ( In some genera, as Physeter, the two processes, upper and lower on each side, are both present and well developed in the same vertebra in the region of transition. In others, as Ziphius and Berardius, they are not both developed on any single vertebra.) Costal cartilages not ossified.

Subfamily Physeterinae.—Numerous teeth in the mandible, which are not set in distinct bony alveoli, but in a long groove imperfectly divided, by partial septa, and held in place by the strong, fibrous gum which surrounds them. No distinct lacrymal bone. Cranium strikingly asymmetrical in the region of the narial. apertures, in consequence of the left opening greatly exceeding the right in size.

Physeter. — Upper teeth apparently of uncertain number, rudimentary and functionless, being embedded in the gum. Lower jaw with from 20 to 25 teeth on each side, stout, conical, recurved, and pointed at the apex until they are worn, without enamel. Upper surface of the cranium concave; its posterior and lateral edges raised into a very high and greatly compressed semicircular crest or wall. Zygomatic processes of malar bones thick and massive. Rostrum greatly elongated, broad at the base and gradually tapering to the apex. Upper edge of the mesethmoid forming a roughened irregular projection between the narial apertures, inclining to the left side. Mandible exceedingly long and narrow, the symphysis being more than half the length of the ramus. Vertebrae: C 7, D11,

I. 8, C 24; total 50. Atlas free; all the other cervical vertebra united by their bodies and spines into a single mass. Eleventh pair of ribs rudimentary. Head about one-third the length of the body; very massive, high and truncated, and rather compressed in front; owing its huge size and remarkable form mainly to the great accumulation of a peculiarly modified form of adipose tissue filling the large hollow on the upper surface of the cranium and overlying the rostrum. The single blowhole is longitudinal, slightly sigmoid, and placed at the upper and anterior extremity of the head to the left side of the middle line. The opening of the mouth is on the under side of the head, considerably behind the end of the snout. Pectoral fin short, broad, and truncated. Dorsal fin a mere low protuberance.

There is no certain evidence that more than one species of this genus exists. This is the Cachalot or Sperm Whale, P. macro- •cephalus, one of the most colossal of animals, quite equalling, if not exceeding, the Greenland Whale in bulk. The length of the full-grown male is from 55 to 60 feet, but the female is stated not to reach more than half that size. It feeds chiefly on cephalopods and fish, and is one of the most extensively distributed of Cetaceans, being met with, usually in herds or “schools,” in almost all tropical or subtropical seas, but not occurring, except accidentally, in the polar regions. Those that appear occasionally on the British coasts are solitary stragglers, usually, if not always, old males. The oil contained in the great cavity above the skull' when refined, yields “spermaceti,” and the thick covering of blubber which everywhere envelops the body produces the valuable “sperm oil” of commerce; hence this animal has long been the subject of a regular chase, by which its numbers have been greatly diminished. The substance called “ambergris,” largely used in perfumery, is a concretion formed in the intestine of the Sperm Whale, and is found floating on the surface of the seas which they inhabit. Its genuineness is attested by the presence of the debris of the horny beaks of the cephalopods on which the Whales feed.

Kogia.— Teeth of the upper jaw absent or reduced to a rudimentary pair in front; in lower jaw 9 to 12 on each side, rather long, slender, pointed, and curved, with a coating of enamel. Upper surface of the cranium concave, with thick, raised, posterior and lateral margins, massive and rounded at their anterior terminations above the orbits. Upper edge of the mesethmoid forming a prominent sinuous ridge, constituting a kind of longitudinal septum do the base of the great supra-cranial cavity. Rostrum not longer than the cranial portion of the skull, broad at the base, and rapidly tapering to the apex. Zygomatic process of the malar styliform. Mandible with symphysis less than half the length of the entire ramus. Vertebra: C 7, D 13 or 14, I. and C 30; total 50 or 51. All the cervical vertebra united by their bodies and arches. External characters not well known, but, judging by the somewhat conflicting accounts of those that have had an opportunity of observing them, the head is about one-sixth of the length of the body, and obtusely pointed in front; the mouth small and placed far below the apex of the snout; the spiracle crescentic, and placed obliquely on the top of the head anteriorly to the eyes, and to the left of the middle line; the pectoral fins are obtusely falcate; and there is a triangular dorsal fin.

The history of this genus is a good illustration of the difficulties in which the study of the Cetacea has been involved by the superficial manner in which it has been investigated. The first known example, a skull from the Cape of Good Hope in the Paris Museum, was described by Blainville under the name of Physeter breviceps. This was afterwards with good reason generically separated by Gray. Until within a very few years ago only five other individuals had been met with, each of which had been described under a different specific name (viz., grayi, macleayi, simus, floweri, and potsii), and which are arranged by Gray in two distinct genera. The most careful examination of the description given of these specimens, or of the now numerous osteological remains available, fails to detect any differences beyond those which may be attributed to age or sex; and hence, according to our present knowledge, these six supposed species must all be included under one name, K. breviceps, an animal which appears to attain the length of 10 feet when adult, and has been met -with at various distant localities in the Southern Ocean, and also off the coast of Madras and in the North Pacific.

Subfamily Ziphiinae.—Teeth of the mandible quite rudimentary and concealed in the gum, except one, or very rarely two, pairs which may be largely developed, especially in the male sex. A distinct lacrymal bone. Externally the mouth is produced into a slender rostrum or beak, from above which the rounded eminence formed by a cushion of fat resting on the cranium in front of the blowhole rises somewhat abruptly. Spiracle or blowhole single, crescentic, median, as in the Delphinidae. Pectoral fin small, ovate, the five digits all moderately well developed. A small obtusely falcate dorsal fin situated considerably behind the middle of the back. Longitudinal grooves on each side of the skin of the throat, diverging posteriorly, and nearly meeting in front. In external characters and habits the animals of this group closely resemble each other. They appear to be almost exclusively feeders on various species of cephalopods, and occur either singly, in pairs, or in small herds. By their dental and osteological characters they are easily separated iiιto four distinct genera.

Hyperoodon.— A small conical pointed tooth at the apex of each ramus of the mandible, concealed by the gum during life. Skull with the upper ends of the premaxillae rising suddenly behind the nares to the vertex and expanded laterally, their outer edges curving backwards and their anterior surfaces arching forwards and overhanging the nares; the right larger than the left. Nasal bones lying in the hollow between the upper extremities of the premaxillae, strongly concave in the middle line and in front; their outer edges, especially that of the right, expanded over the front of the inner border of the maxilla. Very high longitudinal crests on the maxillae at the base of the rostrum, extending backwards almost to the nares, approaching each other in the middle line above; sometimes compressed and sometimes so massive that their inner edges come almost in contact. Anteorbital notch distinct. Mesethmoid but slightly ossified. Vertebra: C 7, D 9, I. 10, C 19; total 45. All the cervical vertebra united. Upper surface of the head in front of the blowhole very prominent and rounded, rising abruptly from above the small, distinct snout.

Two species are known, II. rostratus, the common Hyperoodon or Bottle-nose, and II. ιatifrons, both inhabitants of the North Atlantic, and attaining when adult respectively the length of 24 and 30 feet.

Ziphius.— A single conical tooth of moderate size on each side of the mandible close to the anterior extremity, and directed forwards and upwards. Skull with the premaxillae immediately in front and at the sides of the nares expanded, hollowed, and with elevated lateral margins, the posterior ends rising to the vertex and curving forwards, the right being considerably more developed than the left; the conjoint nasals forming a strongly pronounced symmetrical eminence at the top of the cranium, projecting forwards over the nares, flat above, most prominent and rounded in the middle line in front, and separated by a notch on each side from the premaxillae. Anteorbital notch not distinct. Rostrum (seen from above) triangular, gradually tapering from the base to the apex; upper and outer edges of maxillae at base of rostrum raised into low roughened tuberosities. Mesethmoid cartilage densely ossified in adult age, and coalescing with the surrounding bones of the rostrum. Vertebra: C 7, D 10, I. 10, C 22; total 49. The three anterior cervical vertebra united, the rest free.

The type of this genus is Z. cavirostris of Cuvier, founded upon an imperfect skull picked up in 1804 on the Mediterranean coast of France, and described and figured in the Ossemens Fossiles under the impression that it was that of an extinct species. Many other individuals have, however, been subsequently met with in various parts of the world, from the Shetland Islands to New Zealand, all referable to the same genus if not to the same species; although, as is usual in such cases, they have mostly been described under different names. Teeth, apparently of allied forms, are abundantly found in the Suffolk and Antwerp Crags.

Mesoplodon. — A much compressed and pointed tooth in each ramus of the mandible, variously situated, but generally at some distance behind the apex; its point directed upwards, and often somewhat backwards, occasionally developed to a great size. Skull with the region around the nares as in Hyperoodon, except that the nasals are narrow and more sunk between the upper ends of the premaxillae; like those of Hyperoodon, they are concave in the middle line in front and above. No maxillary tuberosities. Anteorbital notch not very distinct. Rostrum long and narrow. Mesethmoid in adult age ossified in its entire length, and coalescing with the surrounding bones. Vertebrae: C 7, D 10, I. 10 or 11, C 19 or 20; total 46 to 48. Two or three anterior cervicals united, the rest usually free.

Though varying in form, the mandibular teeth of the different members of this genus agree in their essential structure, having a small and pointed enamel-covered crown, composed of true dentine, which, instead of surmounting a root of the ordinary character, is raised upon a solid mass of osteodentine, the continuous growth of which greatly alters the form and general appearance of the organ as age advances, as seen most strikingly in the case of Μ. layardi, where the long, narrow, flat, strap-like teeth, curving inwards at their extremities, actually meet over the rostrum, and must greatly interfere with the movements of the jaw. In one species (Μ. grayi) a row of minute, conical, pointed teeth, like those bf ordinary Dolphins, 17 to 19 in number, are present even in the adults, on each side of the middle part of the upper jaw, but embedded by their roots only in the gum, and not in bony alveoli. This fact, with the frequent presence of rudimentary teeth in other species of this and the last genus in both upper and lower jaws, suggests the idea that the Ziρhioids are derived from ancestral forms having teeth of normal character in both jaws, but whose dentition has become greatly specialized. The existing species of this genus are widely distributed in both northern and southern hemispheres, but most frequent in the latter. The best established are M. bidens, M. curopaeus, Μ. densirostris, Μ. layardi, Μ. grayi, and Μ. hectori; but there is’ still much to be learned with regard to their distinctive characters and geographical distribution. They were abundant in the Later Miocene and Pliocene age, as attested by the frequency with which the most imperishable and easily recognized portion of their structure, the long, cylindrical rostrum of the skull, of more than ivory denseness, is found among the rolled and waterworn fragments of animal remains which compose the well-known “bone-bed” at the base of the Red Crags of Suffolk. Numerous generic distinctions have been founded upon slight modifications of the form of these rostra, such as Choneziphius, Placoziphius, Belemnozιp7ιius, &c., but these can only be considered as provisional until further knowledge is obtained of the structure of the animals to which they belonged.

Berardius. —Two moderate-sized, compressed, pointed teeth on each side of the symphysis of the mandible, with their apices directed forwards, the anterior being the larger of the two and close to the apex. Upper ends of the premaxillae nearly symmetrical, moderately elevated, very slightly expanded, and not curved forward over the nares. Nasals broad, massive, and rounded, of nearly equal size, forming the vertex of the skull, flattened in front, most prominent in the middle line. Anteorbital notch distinct. Rostrum long and narrow. Mesethmoid only partially ossified. Small rugous eminences on the outer edge of the upper surface of the maxillae at base of rostrum. Vertebrae: C 7, D 10, I. 12, C 19; total 48. The three anterior cervicale ankylosed, the rest free and well developed.

The only known species, B. arnouxi, attains the length of 30 feet, and has hitherto only been met with in the seas around New Zealand.

Family Squalodontidae.

Numerous extinct forms, chiefly known by teeth and fragments of crania, may be provisionally placed z7 here, until more of their osteological characters shall be brought to light. They differ from all existing Cetaceans in having the teeth distinctly differentiated into groups, as in the Archaeoceti, the posterior molars being two-rooted. The cranium, has, however, none of the distinguishing characteristics of the Zeuglodons, but essentially resembles that of the Odontoceti, especially in the position of the anterior nares and form of the nasal bones.

The best-known are associated in the genus Squalodon. Dentition: ⅜> c T· simple teeth of the molar series (premolars ?) ⅜, two-rooted molars ∣∙=⅛⅜; total 60. The double-rooted molars differ from those of Zexιglodon in having the denticulations of the crown confined to the posterior border, or at all events much less developed on the front edge. Very little is known of the structure of these animals, beyond the skull and teeth, fragments of which have been found widely distributed throughout the marine Miocene and Early Pliocene formations of Europe, especially in the Vienna basin, many parts of France, and the Antwerp and Suffolk Crags. They have also been found in formations of corresponding age in North America and South Australia.

Family Platanistidae

Under this heading may be placed three very singular genera, which, though differing considerably from each other, Lave several points in common, and do not altogether come under the definition either of the Physcteridae or the Delphinidae, especially in the important character of the mode of articulation of the ribs with the dorsal vertebrae, as the tubercular and capitular articulations, distinct at the commencement of the series, gradually blend together, as they do in most ordinary mammals. The cervical vertebrae are all free. The lacrymal bone is not distinct from the malar. The jaws are long and narrow, with numerous teeth in both. The symphysis of the mandible exceeds half the length of the whole ramus. Externally the head is divided from the body by a slightly constricted neck. Pectoral limbs broad and truncated. Dorsal fin small or obsolete. Fluviatile or estuarine. There are three distinct genera, which might almost be made the types of families, but it is probably more convenient to keep them together.

Platanista.— Teeth about ∣⅜ on each side, set near together, rather large, cylindrical, and sharp-pointed in the young; in old animals acquiring a large laterally compressed base, which in the posterior part of the series becomes irregularly divided into roots. As the conical enamel-covered crown wears away, the teeth of the young and old animals have a totally different appearance. The rostrum and dentigerous portion of the mandible are so narrow that the teeth of the two sides are almost in contact. Maxillae supporting very large, incurved, compressed bony crests, which overarch the nares and base of the rostrum, and almost meet in the middle line above. Orbits very small and eyes rudimentary, without crystalline lens. External respiratory aperture longitudinal, linear. Vertebrae: C 7, D 11, I. 8, C 25; total 51. A small caecum. No pelvic bones. Dorsal fin represented by a low ridge.

One species, P. gangetica, entirely fluviatile, being extensively distributed throughout nearly the whole of the river systems, not only of the Ganges, but of the Brahmaputra and Indus, ascending as high as there is water enough to swim in, but never passing out to It is quite blind, and feeds on small fish and Crustacea, groping for them with its long snout in the muddy water at the bottom of the rivers. It attains the length of 8 feet.

Inia.— Teeth variable, from 26 to 33 on each side of each jaw; those at the posterior part with a distinct tubercle at the inner side of the base of the crown. Vertebrae: C 7, D 13, I. 3, C18; total 41. Transverse processes of lumbar vertebrae very broad. Sternum short and broad, and consisting of a single segment only. Dorsal fin a mere ridge. The long cylindrical rostrum externally furnished with scattered, stout, and crisp hairs. One species only is known, I. geoffr ensis, about 8 feet in length, inhabiting the upper Amazon and its tributary streams.

Pontoporia.— Teeth 50 to 60 on each side of each jaw, with a cingulum at the base of the crown. Jaws very long and slender. Vertebrae: C 7, D 10, I. 5, C19; total 41. Transverse processesof the lumbar vertebrae extremely broad. Sternum elongated, composed of two segments, with four sternal ribs attached. Dorsal fin rather small, triangular, pointed. External respiratory aperture transverse, crescentic. This genus connects the last two forms with the true Delphinidae. The only species, P. blainυillii, is one of the smallest of the whole order, not exceeding 5 feet in length. It has only been met with at the mouth of the Rio de la Plata, near Buenos Ayres, and there is at present no evidence that it ascends into the fresh waters of the river.

Family Delphinidae.

Teeth usually numerous in both jaws. Pterygoid bones short, thin, each involuted to form with a process of the palate bone the outer wall of the post-palatine air-sinus. Symphysis of mandible short, or moderate, never exceeding one-third of the length of the ramus. Lacrymal bone not distinct from the jugal. Transverse processes of the dorsal vertebrae gradually transferred from the arches to the bodies of the vertebrae without any sudden break, and becoming posteriorly continuous serially with the transverse processes of the lumbar vertebrae. Anterior ribs attached to the transverse process by the tubercle, and to the body of the vertebra by the head; the latter attachment lost in the posterior ribs. Sternal ribs firmly ossified. External respiratory aperture transverse, crescentic, with the horns of the crescent pointing forwards.

A very large group, closely united in essential characters but presenting great modifications in details. The different types are mostly so connected by intermediate or osculant forms that there are great difficulties in grouping them into natural subfamilies. Even the formation of well-defined genera is by no means satisfactory in all cases.

Monodon.— Besides some irregular rudimentary teeth, the entire dentition is reduced to a single pair of teeth which lie horizontally in the maxilla, and which in the female remain permanently concealed within the alveolus, so that this sex is practically toothless, while in the male (see fig. 49) the right tooth usually remains similarly concealed and abortive and the left is immensely developed, attaining a length equal to more than half that of the entire animal, projecting horizontally from the head in the form of a cylindrical, or slightly tapering, pointed tusk, without enamel, and with the surface marked by spiral grooves and ridges, runningjn a sinistral direction. (When, as occasionally happens, both tusks are developed, the spiral grooves have the same direction in each.) Vertebrae: C 7, D11, I. 6, C 26; total 50. Cervical region comparatively long, and all the vertebrae . distinct, or with irregular unions towards the middle of the series, the atlas and axis being usually free. Manus small, short, and broad; second and third digits nearly equal, fourth slightly shorter. No dorsal fin.

One species, Λf. monoceros, the Narwhal or Sea-unicorn, so called on account of the remarkable single, horn-like tusk of the male, which often grows to a length of 7 or 8 feet. It inhabits the Arctic Ocean, where it is tolerably abundant and gregarious, feeding on various species of cephalopods, small fish, and crustaceans. It is rarely seen south of 65° N. lat.

Delphinapterus.— This genus is closely allied to the last in external form, as well as anatomical structure, differing only in the very different character of the dentition. Teeth from ⅞ to j⅞, occupying the anterior three-fourths of the rostrum and corresponding portion of the mandible, rather small, conical, and pointed when unworn, but usually become obliquely truncated, separated by intervals considerably wider than the diameter of the tooth, and implanted obliquely, the crowns inclining forwards especially in the upper jaw. Skull rather narrow and elongated, depressed. Premaxillae convex in front of the nares. Rostrum about equal in length to the cranial portion of the skull, triangular, broad at the base, and gradually contracting towards the apex, when it is somewhat curved downwards. Vertebrae: C 7, D 11, I. 9, C 23; total 50. Cervical vertebrae free. Manus broad, short, and rounded, all the digits being tolerably well developed, except the first. Anterior part of head rounded; no distinct snout. No dorsal fin, but a low ridge in its place.

One species, D. leucas (fig. 50). the Beluga, or White Whale, so called from its pure white colour, about 12 feet long, abundant in the Arctic seas, and extending as far south on the American coast as the river St Lawrence, which it ascends for a considerable distance. On rare occasions it has been seen on the coast of Scotland.

In all the remaining genera of Delphinidae the cervical region of the vertebral column is very short, and the first two, and usually more, of the vertebrae are firmly united.

Phocaena. — Teeth f∣ to ⅜⅛, small, occupying nearly the whole length of the rostrum, with compressed, spade-shaped crowns, separated from the root by a constricted neck. Rostrum rather shorter than the cranium proper, broad at the base and tapering towards the apex. Premaxillae raised into tuberosities in front of the nares. The frontal bones forming a somewhat square, elevated protuberance in the middle line of the skull behind the nares, rising altogether above the flattened nasals. Symphysis of mandible very short. Vertebrae: C7, D 13, I. 14, C 30; total 64 (subject to slight individual modifications). First to sixth cervical vertebrae, and sometimes the seventh also, coalesced. Manus of moderate size, oval, slightly falcate; second and third digits nearly equal in length; fourth and fifth well developed, but shorter. Head short, moderately rounded in front of the blowhole. Dorsal fin (in the typical species) near the middle of the back, triangular; its height considerably less than the length of the base; its anterior edge frequently furnished with one or more rows of conical homy tubercles.

The common Porpoise or Porpus, P. communis, is the best known of British Cetaceans (see Porpoise). A species from Japan, P. mêlas, closely allied in osteological and dental characters, but which wants the dorsal fin, constitutes the genus Neomeris of Gray. It is entirely black in colour, and has but J-∣ teeth, rather larger proportionally than those of P. communis, but of similar form.

Orcella.— Teeth ¹²/₁₂ to ¹⁴/₁₄, small, conical, pointed, rather closely set, and occupying nearly the whole length of the rostrum. Skull sub-globular, high. Rostrum nearly equal in length to the cranial portion of the skull, tapering. Manus of moderate size, not elongated, but somewhat pointed. All the bones of the digits broader than long, except the proximal phalanges of the index and third fingers. Head globular in front. Dorsal fin rather small, placed behind the middle of the body. Two species, both of small size— O. brevirostris, from the Bay of Bengal, and O. fluminalis, from the Irrawaddy river, from 300 to 900 miles from the sea. Our present knowledge of the anatomy, geographical distribution, and habits of these interesting Cetaceans is almost entirely due to the researches of Dr J. Anderson. Orca.— Teeth about ⅛⅜, occupying nearly the whole length of the rostrum, very large and stout, with conical recurved crowns, and large roots, expanded laterally and flattened, or rather hollowed, on the anterior and posterior surfaces. Rostrum about equal in length to the cranial part of the skull, broad and flattened above, rounded in front; premaxillae broad and rather concave in front of the nares, contracted at the middle of the rostrum, and expanding again towards the apex. Vertebrae: C 7, D 11-12, L10, C 23; total 51 or 52. Bodies of the first and second and sometimes the third cervical vertebrae united; the rest free. Pectoral fin very large, ovate, nearly as broad as long. All the phalanges and metacarpals broader than long. General form of body robust. Face short and rounded. Dorsal fin near the middle of the back, very high and pointed.

The animals composing this genus are met with in almost all seas from Greenland to Tasmania, but the number of species is still very uncertain. They are readily known, when swimming in the water, by the high, erect, falcate dorsal fin, whence their common German name of Schτoert-fisch (Sword-fish). By English sailors they are generally known as “Grampuses” or “Killers.” They are distinguished from all their allies by their great strength and ferocity, being the only Cetaceans which habitually prey on warmblooded animals, for, though fish form part of their food, they also attack and devour Seals, and various species of their own order, not only the smaller Porpoises and Dolphins, but even full-sized Whales, which last they combine in packs to hunt down and destroy, as Wolves do the larger Ruminants.

Pseudorca. —Teeth about ∣⅜. Cranial and dental characters generally like those of Orca, except that the roots of the teeth are cylindrical. Vertebrae: C 7, D 10, I. 9, C 24; total 50. First to sixth or seventh cervical vertebrae united. Bodies of the lumbar vertebrae distinguished from those of the preceding genera by being more elongated, the length being to the width as 3 to 2. Pectoral fin of moderate size, narrow, and pointed. Dorsal fin situated near the middle of the back, of moderate size, falcate. Head in front of the blowhole high, and compressed anteriorly, the snout truncated.

This genus was first known by the discovery of a skull in a subfossil state in a fen in Lincolnshire, named by Professor Owen Phocaena crassidens. Animals of apparently the same species were afterwards met with in small herds on the Danish coast, and fully described by Eeinhardt. Others, subsequently received from Tasmania were supposed at first to indicate a different species, but comparison of a larger series of specimens from , these extremely distant localities fails to establish any characteristic difference, and indicates an immense range of distribution for a species apparently so rare. Its length is about 14 feet, and its colour entirely black.

Globicephalus.— Teeth ∣∈-Jξ, confined to the anterior half of the rostrum and corresponding part of the mandible, small, conical, curved, sharp-pointed when unworn, sometimes deciduous in old age. Skull broad and depressed. Rostrum and cranial portion about equal in length. Upper surface of rostrum broad and flat. Premaxillae strongly concave in front of the nares, as wide at the middle of the rostrum as at the base, or wider, and very nearly or completely concealing the maxillae in the anterior half of this region. Vertebrae: C 7, D 11, I. 12-14, C 28-29; total 58 or 59. Bodies of the anterior five or six cervical vertebrae united. Length of the bodies of the lumbar and anterior caudal vertebrae about equal to their width. Pectoral limb very long and narrow, the second digit the longest, and having as many as 12 or 13 phalanges, the third shorter (with 9 phalanges), the first, fourth, and fifth very short. Fore part of the head very round, in consequence of the great development of a cushion of fat, placed on the rostrum of the skull in front of the blowhole. Dorsal fin low and triangular, the length of its base considerably exceeding its vertical height.

The type of this well-marked genus is G. mêlas, the Pilot Whale, Ca’ing Whale, or Grindhval of the Faroe islanders, which attains the length of 20 feet, and is of nearly uniform black colour, except the middle of the under surface, which is lighter. They are extremely gregarious, and, unlike the Killers, are mild and inoffensive in disposition, feeding principally on cephalopods. Their eminently sociable character constantly leads to their destruction, as when attacked they instinctively rush together and blindly follow the leaders of the herd. In this way many hundreds at a time are frequently, driven ashore and killed, when a herd enters one of the bays or fiords of the Faroe Islands or north of Scotland. Animals of this well-marked genus are found in nearly all seas, and their specific distinctions are not yet made out. Specimens from the Australian coasts, where they are generally called “Blackfish,” are quite indistinguishable, either by external or osteological characters, from those of the North Atlantic.

Grampus. —Teeth none in the upper jaw; in the mandible few (3 to 7 on each side), and confined to the region of the symphysis. Vertebrae: C 7, D 12, I. 19, C 30; total 68. General external characters much as in Globicephalus, but the fore part of the head less rounded, and the pectoral fin less elongated.

But one species, G. griseus, is certainly known, about 13 feet long, and remarkable for its great variability of colour. It has been found, though rarely, in the North

> Atlantic and Mediterranean. A skull from the Cape of Good Hope, which differs slightly from that of the above, has been described under the name of G. τichardsoni. Delphinus.— Teeth very numerous in both jaws, more than ∣⅞, occupying nearly the whole length of the rostrum, small, close-set, conical, pointed, slightly curved. Rostrum more or less elongated, and pointed in front, usually considerably longer than the cranial portion of the skull. Vertebrae: C 7, D12-14, I. and C variable; total 51 to 90. Pectoral fin of moderate size, narrow, pointed, somewhat falcate. First digit rudimentary, the second longest, third nearly equal, fourth and fifth extremely short. Externally the head shows a distinct beak or pointed snout, marked off from the antenarial adipose elevation by a V-shaped groove. Dorsal fin rather large, triangular or falcate, rarely wanting.

This is a large and heterogeneous genus, which probably ought to be divided, but, until more is known of the structure of many of the species than is at present attainable from the scanty materials in our collections, it is impossible to frame a system of subdivision upon a scientific basis. It seems preferable therefore, instead of introducing new names into zoology for groups founded upon trifling differences in the length or width of the rostrum of the skull or the number of the teeth, which may or may not be correlated with other more important structural modifications, to keep provisionally at least the Linnaean term Delphinus for what remains of the family, after eliminating the well-characterized genera previously described.

The true Dolphins, Bottle-noses, or, as they are more commonly called by seafaring people, “Porpoises,” are found in considerable abundance in all seas, and some species are habitually inhabitants of large rivers, as the Amazon. They are all among the smaller members of the order, none exceeding 10 feet in length. Their food is chiefly fish, for the capture of which their long narrow beaks, armed with numerous sharp-pointed teeth, are well adapted, but some appear also to devour crustaceans and molluscs. They are mostly gregarious, and the agility and grace of their movements in the water are constant themes of admiration to the spectators of the scene when a ‘ ‘ school of Porpoises” is observed playing round the bows of a vessel at sea. The type of the genus is the Common Dolphin of the Mediterranean (Zλ delphis, fig. 52), also found in the Atlantic, and of which a closely allied if not identical form is met with in the Australian seas (D.forsteri) and in the North Pacific {D. bairdii). The Tursio (2λ tursio) is another British species of larger size and heavier build, with larger and less numerous teeth; this and several allied forms probably constitute a natural subgroup. The White-beaked and White-sided Dolphins (Z>. albirostris and leucopleurus) of the North Atlantic, and several others from the South and Pacific Seas, with comparatively broad and short rostrum to the skull and very numerous (80 to 90) vertebrae, constitute the genus Lagenorhynchus of Gray. Others, with long narrow rostrum, are associated under the name of Steno, one of which from the Chinese seas (D. sinensis) has but 51 vertebrae. This last is of a pure milk-white colour, but most of the species are variegated with glossy black, various shades of grey, and white, the latter chiefly on the under parts of the body. One species (Z>. peronii) from the South Seas is remarkable for the absence of dorsal fin. It constitutes the genus Leucorhamphus of Lilljeborg, and Delphinapteτus of other authors; this last name, however, was originally bestowed on the Beluga, and should be retained for it.

Bibliography of Cetacea.— D. F. Eschricbt, Untersuchungen über die Nordischen Wallthiere, 1849, contains a copious bibliography of the group up to the date of publication. Since that time numerous monographs on ι-pecial families and genera have been published, and a large illustrated general work, Ostéographie des Cétacés, by P. J. Van Beneden and P. Gervais, 1868-79. See also J. F. Brandt, “Untersuchungen über die Fossilen und Subfossilen Cetaceen Europa’s,” in Mém. de l'Acad. Imp. de St. Pétersbourg, 7th ser. t. xx., 1873; and C. Μ. Scammon, Marine Mammals of the N. IF. Coast of North America, 1874.

Order INSECTIVORA.

Terrestrial, rarely arboreal or natatorial, diphyodont, heterodont, placental mammals of small size, with plantigrade or semiplantigrade, generally pentadactyle, unguiculate feet; with clavicles (except in Potamogale); with more than two incisors in the mandible, and with enamel-coated molars having tuberculated crowns and well-developed roots. The body is clothed with fur, or protected by an armature of spines; the testes are inguinal or placed near the kidneys, and are not received into a scrotum, the penis is pendent or suspended from the wall of the abdomen; the uterus is two-horned and with or without a distinct corpus uteri, the placenta discoidal and deciduate; and the smooth cerebral hemispheres do not extend backwards over the cerebellum.

Representatives of this order are found throughout the temperate and tropical parts of both hemispheres (except South America and Australia), and exhibit much variety both in organization and in habit. The greater number are cursorial, but some (Talpa, Chrysochloris, Oryzorictes) are fossorial, some (Potamogale, Nectogale, Myogale) natatorial, and some (Tupaiidae) arboreal, while the species of one genus (Galeopithecus) glide through the air like Flying Squirrels; to the great majority, however, the term insectivorous is applicable, the aberrant Galeopithecus being alone phytophagous also, while Potamogale is said to feed on fish, and the different species of Moles live chiefly on worms. Notwithstanding the homogeneous nature of their food, much variety prevails in the form and number of their teeth, as will be seen when we come to consider the classification of the species. In many the division into incisors, canines, premolars, and molars may be readily traced, but in others, forming the great majority of the species, such as the Shrews, this is accomplished with difficulty. The dentition of the Insectivora may, however, be considered typical, since from it may be derived, by modification, that of any known species of diphyodont placental Mammalia. This typical dentition is especially noticeable in the genus Gymnura, where the dental formula is— i f, c γ, pm ⅛, m ; total 44 teeth. So also, in their general organization, these animals appear to have departed so little from what must have been the original mammalian type that, were it not for the apparently advanced character of their placentation, they might easily be considered the scarcely modified descendants of the ancestors of all other orders of diphyodont placental mammals. Their study, therefore, affords the best introduction to that of this division especially.

In most Insectivora the cranial cavity is of small relative size, and in none is the brain case elevated to any considerable extent above the face-line. The facial part of the skull is generally much produced, and the premaxillary and nasal bones well developed. The zygomatic arch is usually slender or deficient, the latter being the case in most of the species, and post-orbital processes of the frontals are found only in Galeopithecidae, Tupaiidae, and Macroscelidae. The number of dorsal vertebrae varies from 13 in Tupaia to 19 in Centetes, of lumbar from 3 in Chrysochloris to 6 in Talpa and Sorex, and of caudal from the rudimentary vertebrae of Centetes to the 40 or more well-developed ones of Microgale. Not less variable aro the characters of the vertebrae: the spinous processes may be very long in one species and short in another, though belonging to the same genus; in the Soricidae and in Myogale the neural arches of the cervical vertebrae are very slender; in Soricidae also and in Gymnura the four anterior vertebrae develop large single hypapophyses, and in Galeopithecus the body of each supports posteriorly a pair of hypapophysial tubercles. In Erinaceus, Myogale, and Talpa small oval ossicles are found on the inferior surface» of the lumbar interspaces. In Erinaceus, owing to the thickness of the cord in the cervical region and its abrupt termination, the diameter of the neural canal in the cervical and first two dorsal vertebrae greatly exceeds that of any of the succeeding vertebrae. The sternum is variable, but generally narrow, bilobate in front, and divided into segments. The shoulder-girdle presents remarkable adaptive modifications, most expressed in Talpa (see Mole), having relation to the use of the fore limbs in burrowing; in the Golden Moles (Chrysochloris), however (vide infra), the forearm and manus alone become specially modified. In Galeopithecus and Macroscelides the forearm bones are distally united; in all other known Insectivora the radius and ulna are distinct. The manus has generally five digits, but in Rhynchocyon and in one species of Oryzorictes the pollex is wanting. In the true Moles (see Mole) it is extremely modified. The femur has, in most species, a prominent ridge below the greater trochanter presenting the characters of a third trochanter. In Galeopithecus, Tupaia, Centetes, Hemicentetes, Ericulus, and Solenodon the tibia and fibula are distinct, in all other genera more or less united together. The pes consists usually of five digits (rarely four by reduction of the hallux), and in some, as in the leaping species (Macroscelides, Rhynchocyon), the tarsal bones are greatly elongated. The form of the pelvis, and especially that of the symphysis pubis, varies within certain limits, which have been proposed by Leche as a basis for the classification of the families. Thus in Galeopithecidae, Tupaiidae, and Macroscelidae there is a long symphysis, as in Rodents; in Erinaceidae, Centetidae, and Potamogalidae it is short; and in Soricidae, Talpidae, and Chrysochloridae there is none.

Space does not admit of even attempting a sketch of the interesting modifications of the muscular system, which will be found fully described in the present writer’s Monograph, referred to in the bibliography. As to the nervous system, it may be noticed that the brain throughout the species presents a low type of organization: in none do the cerebral hemispheres present any trace of convolutions, nor do they extend backwards so as to cover the cerebellum; the olfactory lobes are large and project in front; and the corpus callosum is short and thin. In the Hedgehogs (Erinaceus) the spinal column ends abruptly opposite the third or fourth dorsal vertebra in a slender filament; the dorsal and lumbar nerves, given off in front of this point, aie carried backwards in two compressed bundles occupying the suddenly narrowed spinal canal as far as the sacrum.

Owing to the similarity in the character of the food, the truly insectivorous species, forming more than nine-tenths of the order, present little variety in the structure of the digestive organs. Except in Galeopithecus (vide infra) the stomach is a simple, thin-walled sac; in some, as in Centetes and allied genera, the pyloric and oesophageal openings are very close together; the intestinal canal has much the same calibre throughout, and varies from three (in the Shrews) to twelve times (in the Hedgehogs) the length of the head and body. In the arboreal genera, Galeopithecus and Tupaia, and in the allied Macroscelidae, all of which probably feed on vegetable substances as well, most of the species possess a caecum. The liver is deeply divided into lobes, the right and left lateral being cut off by deep fissures; both the caudate and Spigelian lobes are generally well developed, and the gall-bladder, usually large and globular, is placed on the middle of the posterior surface of the right central lobe.

In most of the species (Soricidae, Centetidae, Chryso- chloridae) the penis is capable of being more or less completely retracted within the fold of integument surrounding the anus; in some (Galeopithecidae, Talj>idx) it is pendent in front of the anus, while in others (Macroscelidse, Erinaceidae, Solenodontidae) it is carried forwards anti suspended from the abdominal wall. In Centetinae and Chrysochloris the testes lie immediately behind the kidneys, in others more or less within the pelvis. During the rut they become greatly enlarged, forming protrusions in the inguinal region. Except in Rhynchocyon the uterine cornua are long and open into a short corpus uteri, which in many species (Soricidae, Talpidae, Centetidae, Chrysochloridae) is not separated from the vagina by a distinct os uteri. With the exception of Galeopithecus all Insectivore, appear to be multiparous, the number of foetuses varying from two to eight in Erinaceus, and from twelve to twenty-one in Centetes. The position of the mammary glands and the number of the teats vary greatly. In Galeopithecus there are two pairs of axillary teats, in Solenodon a single pair post-inguinal, but in most species they range from the thorax to the abdomen, varying from two pairs in Gymnura to twelve in Centetes. In Chrysochloris the thoracic and inguinal teats are lodged in deep cup-shaped depressions.

Odoriferous glands exist in many species. In most Shrews they occur on the sides of the body at a short distance behind the axilla, and their exudation is probably protective, as few carnivorous animals will eat their dead bodies. In both species of Gymnura and in Potamogale large pouches are situated on either side of the rectum, and discharge their secretions by ducts, opening in the first-named genus in front of and in the latter within the margin of the anus. In Centetes racemose glands similarly situated discharge by pores opening at the bottom of deep pits placed at either side of the anus.

The integument is thin, but in many species lined with well-developed muscles, which are probably more developed in the Hedgehogs JErinaceidae) than in any other mammal; in this family and in Centetidae most of the species are protected by spines implanted in the panniculus carnosus, and more or less replacing the fur of the upper surface of the body.

The Insectivora are divisible into two very distinct suborders, of which the first includes a single genus only.

Suborder I. Dermoptera.

Upper and lower incisors compressed, multicuspidate, the lower deeply pectinate; anterior and posterior limbs connected by a broad integumentary expansion forming a parachute. Family I. Galeopithecidae. Suborder II. Insectivora Vera.

Upper and lower incisors conical, unicuspidate or with basal cusps only, the lower not pectinate; limbs free, formed for terrestrial progression. [table] [table]

Family Galeopithecidae.

The characters of the family are those of the suborder Dermoptera, to which may be added that the orbit is nearly surrounded by bone, the zygomatic arches are well developed, the tympanies form bullae osseae, the ulna is distally united with the radius, the tibia and fibula are distinct, the pubic symphysis is long, the penis is pendent, the testes are received into inguinal pouches, the mammae are axillary, the uterus is two-horned, and there is a large caecum.

Galeopithecus (i ⅜, c ∣ , pm ⅜, m ⅛; second upper incisors and canines with two roots), with two species— G. volans and G. philip∙ pinensis. The former, the Flying Lemur of Linnaeus, distinguished from the latter by the form of the upper incisors, has a total length of nearly 2 feet. The long and slender limbs are connected by a broad integumentary expansion extending outwards from the sides of the neck and body, and forming also a web between the fingers and toes as far as the base of the claws (fig. 53); the hind limbs are further connected by a similar expansion passing outwards along the back of the feet to the base of the claws, and, inwardly, involving the long tail to the tip, forming a true interfemoral membrane, as in the Bats.

The species of this family live in the forests of the Malay Peninsula, Sumatra, Borneo, and the Philippine Islands, where they feed chiefly on the leaves of trees, and probably also on insects. Their habits are nocturnal, and during the daytime they cling to the trunks or limbs of trees head downwards in a state of repose. With the approach of night their season of activity commences, when they may be occasionally seen gliding from tree to tree supported on their cutaneous parachute, and they have been noticed as capable of traversing in this way a space of 70 yards with a descent of only about one in five.

Galeopithecus was referred by some of the older zoologists and anatomists to the Bats, and by others (and even in lately published works) to the Lemurs, but Professor Peters’s view (in which most subsequent writers agree) that it belongs to neither of these orders, and must be considered an aberrant Insectivore, appears to be undoubtedly the correct one. Besides differing from the Bats altogether in the form of the anterior limbs and of the double-rooted outer incisors and canines, it also contrasts strongly with them in the presence of a large sacculated caecum, and in the great length of the colon, which is so remarkably short in all the Chiroptera. From the Lemurs, on the other hand, the form of the brain, the character of the teeth, the structure of the skull, and the deciduate discoidal placenta at once separate it.

Family Tupaiidae.

Arboreal Insectivora, with comparatively large brain case, orbits encircled with bone, and well-developed zygomatic arches. The malar bone is perforated; the tympanies form bullae; the pubic symphysis is long; the tibia and fibula are distinct, the metatarsus but little longer than the tarsus; the molars are broad, with W-shaped cusps; and the intestinal canal has generally a short caecum.

The animals included in this family are all arboreal, resembling Squirrels closely both in habits and in external form; they are divided into two genera having the same dental formula (ι ⅜, c ⅛, pm ⅜, m ⅜), but distinguished by the form of the skull. Tupaia, •with nine species, is found in India, Burmah, the Malay Peninsula, Nicobars, Sumatra, Java, and P>orneo. The species closely resemble one another, differing chiefly in size and in the colour and length of the fur. Nearly all have long bushy tails, which still further increase their resemblance to Squirrels. Their food consists of insects and fruit, which they usually seek for in the trees, but also occasionally on the ground. When feeding they often sit on their haunches, holding the food, after the manner of Squirrels, between their fore paws. Ptilocercus includes a single very interesting species, Pt. lowii, inhabiting Borneo, remarkable for its long tail, two-thirds naked, having the terminal third furnished with a double fringe of long hairs. Its habits are probably similar to those of the Tupaias, of which it may be further noticed that they alone among Insectivora are day-feeders.

Family Macroscelidae.

Terrestrial Insectivora, with comparatively large brain case, well-developed zygomatic arches, and tympanic bullae; but the orbits are not encircled by bone, the malar is imperforate, and there are generally no post-orbital processes. The pubic symphysis is long, the tibia and fibula united high up, the metatarsus much longer than the tarsus, the molars broad and quadricuspidate, and the intestinal canal has a large caecum.

These leaping Insectivores are easily distinguished by the great length of their metatarsal bones. All the species are African, and are divisible into two genera :—

a . i f, c f, pm ⅞, m ⅜ or ∣; forearm bones united below. Macroscdides. b . i ⅜ (or ⅜), c ⅜, pm ⅜, m ⅜; forearm bones separate. Rhynchocyon. Macroscelides includes ten species widely distributed throughout the African continent. All are closely related, resembling one another in general forms, and even in the colour of the fur. They fall into two groups distinguished by the presence or absence of a small lower fourth molar. Μ. tetradactylus (fig. 55),.type of the subgenus Petrodromus, differs from all in the absence of the hallux. Of Rhynchocyon four closely allied species have been described, all from East Africa.

Family Erinaceidae.

Terrestrial Insectivora, with a small brain case, without postorbital processes, with slender (rarely imperfect) zygomatic arches, with a short pubic symphysis, and with the tibia and fibula united above. The tympanies are annular, not forming bullae; the intestine has no caecum; the penis is carried forwards, and suspended from the wall of the abdomen; and the upper true molars have each four principal cusps and a small central fifth cusp very characteristic of the family.

Subfamily I. Gymnurinøe.—Caudal vertebrae numerous; palate bones completely ossified; pelvis very narrow; fur without spines.

Gymnura, i ⅜, c ⅜, pm ∣ , m ⅞, with two species, G. rafflesii and G. suilla, from the Malay Peninsula and Indian Archipelago. The former has the appearance of a large Rat with a long head and projecting mobile snout; the latter, much smaller, with a short tail and small third upper premolar, has long been known under the name of Hylomys suillus, and classed with the Tupaiidae. Both species present a very generalized type of dentition, in this respect occupying an almost central position in the order.

Subfamily II. Erinaceinae.—Caudal vertebrae rudimentary; palate bones with defects of ossification; pelvis wide; fur with spines.

Erinaceus, i ∣ , c ⅛, pm ⅜, m ⅜, includes nineteen species (familiarly known as Hedgehogs) distributed throughout Europe, Africa, and the greater part of Asia, but they have not been found in Madagascar, Ceylon, Burmah, Siam, the Malay Peninsula and Archipelago, or Australia. All the species resemble one another closely in the armature of spines which invests the upper surface and side of the body; and all possess the power of rolling themselves up into the form of a ball protected on all sides by strong spines, the dorsal integument being brought downwards and inwards over the head and tail, so as to include the limbs also, by the action of special muscles (for description see Monograph of the Insectivora referred to in the bibliography). The common Hedgehog ( E. europaeus) is the most aberrant species, differing from all the rest in the peculiarly shaped and single-rooted third incisors and first upper premolars (fig. 56, A), and in its very coarse harsh fur. The dentition of the long-eared North Indian form, E. grayi (fig. 56, B), may be considered characteristic of all the other species, the only important differences being found in the variable size and position of the second upper premolar, which is very small, external, and deciduous in the Indian species E. micropus and pictus. The former species, limited to South India, is further distinguished by the absence of the malar bone. Of African species, E. diadematus, with long frontal spines, is probably the commonest, and E. albiventris has been made the type of a separate genus on account of the total absence of the hallux.

Family Soricidae.

Terrestrial, rarely natatorial, Insectivora, with narrow elongated skulls, without post-orbital processes or zygomatic arches. The tympanies are annular, not forming bullae; there is no symphysis pubis; the intestine has no caecum; the tibia and fibula are united; and the molars have well-developed W·shaped cusps.

The dentition is very characteristic of the family; in all the upper front incisors are large, with a more or less prominent posterior basal cusp, and between these and the last premolar intervene a variable number of small incisors and premolars, among which the small canine can be distinguished only by its position immediately behind the premaxillary suture. The number of teeth in the mandible is always twelve, and the single pair of incisors are much extended horizontally forwards, the canine is the smallest tooth, and the single premolar is not much larger (see fig. 57).

The Shrews thus form a very compact family, which includes considerably more than half the known species of Insectivora, and of which the geographical distribution is coextensive with that of the order. They have been divided into several genera (so-called) and subgenera, depending chiefly on the number of the upper incisors and premolars, and on the colour of the teeth. The best arrangement appears to be that proposed by Μ. Alph. Milne-Edwards, as follows :— A. Terrestrial: feet without a border composed of stiff hairs. [table]

Anourosorex includes A. squamipes, a Mole-like species, with very short ears and tail, from Tibet. Biplomesodon, with one species, D. pulchellus, from the Kirghiz steppes, though agreeing in the number of teeth, is Shrew-like in external form. Crocidura, 28-30 teeth, with about seventy species divided into four subgenera, comprises the greater number of white-toothed Old-World Shrews, having a round tail thinly clothed with a few hairs of unequal length. C. aranea and C. suaveolens of the continent of Europe, and C. indicus, the Musk-Rat of India, are well-known examples. Sorex, the typical genus (see Shrew), also divided into four subgenera, with Blarina, includes all the species with brown teeth and angular uniformly hairy tail. Neosorex includes the New-World and Crossopus (see Shrew) the Old-World amphibious species, having a fringe of stiff hairs along the sides of the feet, and Nectogale a very remarkable species from Tibet, N. elegans (fig. 58), distinguished from all other Shrews by the webbed condition of the toes, and the presence of adhesive cushions on the under surface of the feet, which enable the animal to hold on to smooth stones at the bottom of rushing torrents.

Family Talpidae.

Fossorial, rarely natatorial, Insectivora, distinguished from the Soricidae by the presence of zygomatic arches and tympanic bullae osseae, and by the form of the teeth. The eyes are very small, in some species covered with skin; the ears are short and concealed by the fur; the fore limbs are generally more or less modified for digging; there is no symphysis pubis; the intestine has no caecum; the tibia and fibula are united; and the nnicuspidate upper and lower front incisors are not extended horizontally forwards.

This family, though thus easily distinguished, is, nevertheless, evidently closely related to the Shrews, with which such intermediate forms as those included in the genera Urotrichus and Uropsilus connect it. In striking contrast with the Shrews, however, the distribution of the Moles is limited to the temperate regions of Europe, Asia, and North America.

Subfamily I. Myogalinae.—Clavicles and humeri moderately elongated: manus without os falciforme. [table]

Myogale includes two very remarkable species, Μ. moschata and Μ. pyrenaica. The former is by far the largest species of the family, its total length being about 16 inches. Its long proboscislike snout projects far beyond the margin of the upper lip; the toes are webbed as far as the bases of the claws; and the long scaly tail is laterally flattened, forming a powerful instrument of propulsion when swimming. This species inhabits the banks of streams and lakes in south-east Russia, where i½ food consists of various aquatic insects. Μ. pyrenaica, living in a similar manner in the region of the Pyrenees, is very much smaller, has a round tail, and a proportionally longer snout. Urotrichus, with pm ⅜, and Neurotrichus (subg.), withjwιf, are represented by two small Molelike species, externally resembling one another closely, from Japan and North America respectively. Of Uropsilus, U. soricipes, from the borders of Tibet, is a very interesting species, having the external form of a Shrew but the skull of a Mole.

Subfamily II. Talpinae (True Moles).—Clavicles and humeri very short and broad; manus with a large os falciforme.

A. Front upper incisors much larger than the second pair (New-Wr>rl∣ι M∩lesk [table]

Scaptonyx, with a single species S. fusicaudatxιs, from west China, connects Urotrichus with the true Moles. Talpa includes seven species, of which the Common Mole is a familiar example. See Mole. Family Potamogalidae. Insectivora with a small brain case, without post orbital processes or zygomatic arches, and with annular tympanies not forming bullae. There are no clavicles; the pubic bones are connected by a ligament, and there is no true symphysis; the intestine has no caecum; the tibia and fibula are united low down; and the upper true molars have broadly V-shaped cusps presenting characters intermediate between those of the preceding and succeeding families.

Potamogale, i ⅜, c ⅛, pm ∣ , m ⅜, with P. velox. This most interesting species inhabits the banks of streams in west equatorial Africa, and its whole structure indicates an aquatic life. It is nearly 2 feet in length, the tail measuring about half. The long cylindrical body is continued uninterruptedly into the thick laterally compressed tail, the legs are very short, and the toes are not webbed, progression through the water evidently depending wholly on the action of the powerful tail, while the limbs are folded inwards and backwards. The muzzle is broad and flat, and the nostrils are protected by valves. The fur is dark brown above, the extremities of the hairs on the back being of a metallic violet hue by reflected light, beneath whitish.

Geogale, if, c ∣, pm ⅝, m f, with G. aurita, a small Mouse-like species from Madagascar, agrees closely with Potamogale in the general form of the skull and teeth; the tibia and fibula are distinct, but it is not known whether a clavicle exists or not, and the material at present available is insufficient to definitely fix the natural position of the species.

Family Solenodontidae. Insectivora with a small brain case constricted between the orbits, and without post-orbital processes or zygomatic arches. The penis is carried forwards and suspended from the abdomen; the testes are received into perineal pouches; the mammary glands are post-inguinal; the uterine cornua end. in caecal sacs; the intestine has no caecum; the tympanies are annular; the upper true molars have V-shaped crowns; the symphysis pubis is short; and the tibia and fibula are distinct.

Solenodon, i ⅜, c f, pm ⅜, m ⅜, with S. paradoxus and S. cubanus, from Hayti and Cuba respectively, alone represents the family. These species, which differ chiefly in the colour and quality of the fur, have each a remarkably long cylindrical snout, a long naked tail, feet formed for running, and the body clothed with long, coarse fur.

The position of the mammae quite behind on the buttocks is unique among Insectivora. The upper front incisors are much enlarged, and with the other incisors, canines, and premolars closely resemble those of Myogale ; the second lower incisors are, as in Potamogale, much larger than the anterior pair, and are deeply hollowed out internally. While thus apparently showing relationship with the Talpidae, the form of the crowns of the molar teeth connects them with the next family.

Family Centetidae. Insectivora with a small cylindrical brain case not constricted between the orbits, and without post-orbital processes or zygomatic arches. The penis is pendent and retractible within the fold of the integument surrounding the anus; the testes are abdominal; the mammary glands are thoracic and ventral; the uterine cornua are terminated by the Fallopian tubes; the intestine has no caecum; the tympanies are annular; the molars have V-shaped crowns; the pubic symphysis is short, and the tibia and fibula separate or united. All the known species are limited to Madagascar.

Subfamily I. Centetinae. —Tibia and fibula distinct; testes near kidneys; fur with spines.

Centetes, i ⅜ or ⅜, c ⅜, pm ⅜, m ⅞ or ⅜. The single species, C. ecaudatus, the well-known taillessGround-Hog of Madagascar, attains a total length of from 12 to 16 inches, and is the largest known Insectivore. The adult males have exceedingly long canines, the extremities of the lower pair being received into pits in front of the upper canines. It is probably the most prolific of all mammals; as many as twenty-one young are said to have been brought forth at a birth. The young have strong white spines arranged in longitudinal lines along the back, but these are lost in the adult animal, which is provided only with a nuchal crest of long rigid hairs. Hemicentetes, i ⅜, with H. semisρinosus and II. nigriceρs, is distinguished by the persistence of the third upper incisor, and by the form of the skull. The two species are very much smaller than C. ecaudatus, and the dorsal spines are retained in the adult state. Ericulus, i ⅞, has E. setosus, a remarkable Hedgehog-like species having the whole upper surface and even the shôrt tail densely covered with close-set spines. The facial bones are much shorter than in any of the preceding genera, and the upper front incisors are elongated as in Erinaceus. Judging from the slight development of the cutaneous muscles compared with those of the true Hedgehogs, it is probable that complete involution, as in the latter animals, does not take place.

Subfamily II. Oryzorictinεe.—Tibia and fibula united; testes near urethra; fur without spines.

Microgale, i ∣, c B pm ∣ , m ⅜, includes Μ. longicaudata and Μ. cowani, small Mouse-like species, the former with a tail double the length of the head and body; teeth like those of C. ecaudatus, but, owing to the comparatively much shorter muzzle, not separated by wide spaces, and the last premolar and molars with internal basal processes. Oryzorictes contains 0. hova and 0. tetradactylus, the latter distinguished by the presence of four digits only in the manus, the three inner having long laterally compressed fossorial claws. The general form of the head and body of the two species known is that of a Mole. They burrow in the rice-fields, and do much damage to the crops.

Family Chrysochloridae.

Fossorial Insectivora, with conical skulls not constricted between the orbits, with well-developed zygomatic arches and tympanic bullae, but without post-orbital processes. The eyes are covered by the hairy integument, the ears short and concealed by the fur; the internal generative organs and the crowns of the upper molar teeth are as in Centetinae ; the mammary teats are thoracic and inguinal, and placed in cup-shaped depressions; there is no pubic symphysis; and the tibia and fibula are united.

This family is evidently closely allied to Centetidae, occupying the same relative position with respect to that family that Talpidae does to Soricidae. All the species are fossorial, and restricted to south Africa. In all the forearm and manus are similarly modified for digging, but in a manner very different from that observable in Talpidae (see^MθLE).

Chrysochloris, i ⅜, c f, pm f, m ⅜ or ⅜, embraces seven or eight species. Those with m ⅜, with a basal talon to the lower grinders, and without a prominence in the temporal fossa, have been placed in a separate genus Calcochloris by Professor Mivart. Nearly all the species have the fur of the upper surface of a brilliant metallic lustre, varying from golden bronze to green and violet of different shades.

Fossil Insectivora.

Of fossil Insectivora no undoubted traces have been found in deposits earlier than the Eocene. Amphidozotherium, allied to Urotrichus, and Neogymnurus and Protalpa, with relationships to Gymnura and Talpa respectively, have been described from the lacustrine Eocene beds of Quercy. Several genera with insectivorous affinities have been characterized by Cope and Marsh from remains found in the Eocene of Wyoming, but these have been relegated to distinct suborders of a new order Bunodonta, of which Insectivora is considered a suborder only. The Miocene deposits of the south of France and Germany have yielded fossil forms of Erinaceidae (Amphechinus, Galerix, Tetr deus'), of Soricidae (Sorex, Mysarachne, Plesiosorex), and of Talpidae (Dimylus, Galeospalax, Gcotrypus, IIyporissus, Myogale). Of the latter family Galeospalax has been characterized from the Pliocene of Norfolk; and remains of the common Hedgehog, and of some of the existing species of Sorex, have been found in various post-Tertiary deposits.

Bibliography of Insectivora.— Peters, Reise nach Mossambique— Säugeth., 1852; Id., “Ueberdie Classification der Insectivora,” Monatsb. Aka<l. Wissensch. Berlin, 1865, and other papers; Mivart, “On the Osteology of the Insectivora,” Jour. Anat. and Phys., 1867. 1868, and Proc. Zool. Soc., 1871; Gill, “Synopsis of Insectivorous Mammals,” Bull. Geol. and Geog. Survey, U.S.A., Washington, 1875 (includes a general bibliography of the order Insectivora) ; Dobson, Monograph of the Insectivora, Systematic and Anatomical, London, 1882.

Order CHIROPTERA.

Volant mammals, having their fore limbs specially modified for flight. The forearm consists of a rudimentary ulna, a long curved radius, and a carpus of six bones supporting a thumb and four greatly elongated fingers, between which, the sides of the body, and the hinder extremities a thin expansion of the integument (the wingmembrane) is spread out. The knee is directed backwards, owing to the rotation of the hind limb outwards by the wing-membrane; a peculiar elongated cartilaginous process (the calcaneum or calcar), rarely rudimentary or absent, arising from the inner side of the ankle-joint, is directed inwards, and supports part of the posterior margin of an accessory membrane of flight, extending from the tail or posterior extremity of the body to the hinder limbs (the inter-femoral membrane). The penis is pendent; the testes abdominal or inguinal; the mammary glands thoracic and generally post-axillary; the uterus simple cr with more or less long cornua; the placenta discoidal and deciduate; and the smooth cerebral hemispheres do not extend backwards over the cerebellum. The dental series consists of four kinds of teeth—incisors, canines, premolars, and molars; and the dental formula never exceeds i ⅜, c τ> P m ¾ m ⅜ > tota l 38 teeth.

The animals comprised in this order are at once distinguished by the presence of true wings, and this peculiarity is accompanied by other modifications of bodily structure having special relation to aerial locomotion. Thus, in direct contrast to all other mιmmals, in which locomotion is chiefly effected by action from behind, and the hind limbs consequently greatly preponderate in size over the fore, in the Chiropteτa the fore limbs, being the only agents in propelling the body forward during flight, immensely exceed the short and weak hinder extremities; the thorax, giving origin to the great muscles which sustain flight, and containing the proportionately (compared with other mammals) very large lungs and heart, is remarkably capacious, and the ribs are flattened and close together; the shoulder-girdle is also greatly developed in comparison with the weak pelvic bones.

Linnaeus included the Bats among the Primates, mainly on account of the number of their upper incisors, supposed to be always four, the thoracic position of the mammae, and the pendent condition of the penis. Many other zoologists, taking into consideration also the placental characters and the form of the uterus, have followed him; but it is evident that the situation of the mammae is related to the necessarily central position of the young during flight, the shortness of the uterine cornua, observable in so many species, to the generally uniparous gestation requiring less room, while the discoid deciduate placenta is equally present in and characteristic of the Insectivora, many species of which have also the penis pendent. Then, all these reasons for maintaining the Bats in such an exalted position being disposed of, we find in the low organization of their brain another proof of their inferior position in the zoological scale, while furthermore, although they differ widely from all other mammals in external form, it is evident that this is but the result of special adaptation to aerial locomotion; and, taking into account their whole bodily structure, we are forced to admit with Professor Huxley that they may be regarded as exceedingly modified Insectivora.

So thoroughly, however, has this adaptation been carried out that of all animals the Bats are the least terrestrial, not one of them being equally well fitted, as most Birds and Insects are, for progression on the earth. This is due to the hind as well as the fore limbs being pressed into the service of aerial locomotion. The hind limb is so rotated outwards by the wing-membrane that, contrary to what obtains in all other vertebrates, the knee is directed backwards, and corresponds in position to its serial homologue the elbow. When placed on the ground, therefore, the animal rests on all fours, having the knees directed upwards like a grasshopper’s, while, in order to bring the foot into a position for forward progression, it is rotated forwards and inwards on the ankle. Walking under these circumstances is at best only a species of shuffle, and that this is fully recognized by the animal is evidenced by its great anxiety to take to the wing, or, if this be impracticable, to ascend to some point where it can hitch itself up by the claws of the hind-legs in its usual position when at rest.

The bones entering into the formation of the skeleton in Chiroptera are characterized by their slenderness, and by the great size of the medullary canals in those of the extremities. The vertebral column is short, and the vertebrae differ very slightly in number and form throughout the species. The general number of the dorso-lumbar vertebrae is 17, whereof 12 are dorsal; the cervical vertebrae are very broad, but short from before backwards (their breadth is due to the great transverse diameter of the spinal canal rendered necessary by the comparatively very large size of the spinal cord in this position, which, after giving off the nervous supply to the fore limbs and thorax, rapidly diminishes in size, and in the lumbo-sacral region is reduced to a fine thread). Except in the great frugivorous Bats (JPteropodidae), the vertebrae, from the third cervical backwards, are devoid of spinous processes, a characteristic feature in the general osteology of the order. From the first thoracic to the last lumbar vertebra the spinal column forms a single curve backwards, which is most pronounced in the lumbar region. The bodies of the vertebrae are very slightly movable upon each other, and in old individuals appear to become partially ankylosed together. The caudal vertebrae are simple cylindrical bones without processes; their number and length is extremely variable even in closely allied species; and the anterior vertebrae are generally united to the ischial tuberosities. The development of these vertebrae, in fact, is intimately correlated to the habits of the animals, the long tail in the insectivorous species supporting and controlling the position of the large interfemoral membrane which appears not only to aid their rapid doubling motions when in pursuit of their insect prey by acting as a rudder on the air, but also to assist them in the capture and retention of the larger insects; in the frugivorous species, on the other hand, this is not required, and the tail is accordingly rudimentary or absent. In all Bats the presternum has a prominent keel for the attachment of the great pectoral muscles. In most species the ribs are much flattened, and in some partially ankylosed by their contiguous margins.

Great as is the variability of the shape of the skull in Insectivora, it is still greater in Chiroptera, and evidently depends upon the much wider differences in the nature of the food of different species requiring corresponding modifications of the manducatory apparatus, so that extreme modifications may be found in species of the same family, as in the case of the Phyllostomidae. In some genera, however, as in Miniopterus, Furia, Mor mops (vide infra), the peculiar shape of the skull cannot thus be accounted for. As in the Insectivora, post-orbital processes are developed in some species only, as in the Pteropodidae and in a few Nycteridae and Emballonuridae ; in Pteropus leucopter us alone does a process from the zygomatic arch meet the post-orbital so as to complete the orbital ring. Zygomatic arches, though slender, are present in all except in some of the species of Phyllostomidae.

The milk teeth differ from those of all other mammals in that they in no respect resemble in form those of the permanent series. They are very slender, with acutely pointed recurved cusps, and are soon shed, but often coexist for a short time with the permanent teeth when the latter are considerably elevated above the gum. In the family Rhinolophidae the milk teeth are absorbed before birth. The permanent teeth exhibit great variety in form, sometimes even in the same family, as in Phyllostomidae, whilst in other families, as in Rhinolophidae, the resemblance between the dentition of species otherwise differing in many important respects is most remarkable. In all, however, they are provided with well-developed roots, and their crowns are acutely tuberculate, with more or less well-defined W-shaped cusps, in the insectivorous species, as in Insectivora, or variously hollowed out or longitudinally grooved in the frugivorous, as in some species of Phyllostomidae and in the Pteropodidae.

As might be expected, the shoulder-girdle varies very slightly, having the same office to fulfil in all species. The clavicle is very long, strong, and curved; the scapulae large, oval, triangular, with a long curved coracoid process. The humerus, though long, is scarcely two-thirds the length of the radius; the ulna is rudimentary its proximal extremity, which articulates with but a small part of the humerus, is ankylosed with the radius; immediately beyond the joint it is reduced to a very slender splint-like bone, which extends about as far as the middle of the radius. In all species a detached sesamoid bone exists in the tendon of the triceps muscle, and is generally found in skeletons. The radius is very long, in some species as long as the head and body. The proximal row of the carpus consists of a single bone (the united scaphoid, lunar, and cuneiform bones), which, with the extremity of the radius, forms the radio-carpal joint; in the distal row the trapezium, trapezoid, and os magnum vary much in size in the different families; the unciform appears to be the most constant, and the pisiform is generally very small. It will be necessary to again refer to this subject when dealing with the diagnostic characters of the suborders.

The manus is, in all the species, composed of five digits. The first, fourth, and fifth consist each of a metacarpal bone and two osseous phalanges; in the second and third the number of phalanges is different in certain families. The first digit—the pollex—always terminates in a claw, which, with the proximal phalanx, is most developed in the frugivorous species. In most of the species of the frugivorous Pteropodidae the second digit is also provided with a claw, but in all other Bats this and the remaining digits are unarmed. In the genus Triaenops alone a very peculiar short bony process projects from the outer side of the proximal extremity of the terminal phalanx of the fourth digit. The relative development of the digits and their phalanges will be specially treated of under each family.

As might be expected from the small size of the posterior limbs, the pelvic girdle is very weak. The iliac bones are long and narrow. In most species the pubic bones of opposite sides are very loosely united in front in males; in females they are widely separated; in the family Rhinolophidae alone do these bones form a symphysis. The eminentia ileo-pectinea develops in all species a long pectineal process, which in the subfamily Phyllorhininae alone is continued forwards to the anterior extremity of the ilium (vide infra,, p. 412), forming a preacetabular foramen which is unique among mammals. The acetabulum is small and directed outwards, and slightly upwards, and with this is related the peculiar position of the hind limb described above as one of the chief characteristics of the order. The femur is slender and cylindrical, with a small head and very short neck, and scarcely differs in form throughout the species. The bones of the leg and foot are more variable; in the subfamily Molossinae alone is there a well-developed fibula; in all other species this bone is either very slender or cartilaginous and ligamentous in its upper third, or reduced to a small bony process above the heel, as in Megaderma, or altogether absent, as in Nycteris.

The foot consists of a very short tarsus, and of slender, laterally compressed toes, with much curved claws. The first digit is composed of a metacarpal bone, a proximal and an ungual phalanx, and is slightly shorter than the other four toes, which have each an additional phalanx, except in the subfamily Phyllorhininae and in the anomalous genera Thyrσptera and Myxopoda, where all the toes have the same number of phalanges as the first digit, and are equal to it in length. In the very remarkable genus Cheiromeles the first digit is thumb-like and separated from the others; and in the Molossi the first and fifth digits are much thicker than the intermediate toes.

The muscular system, as might be expected, exhibits few striking differences throughout the species. The most noticeable peculiarities in the myology of the order consist in the separated bands or slips into which the platysma is divided, and in the remarkable muscle termed occipito-pollicalis, which extends from the occipital bone to the base of the terminal phalanx of the pollex (see Macalister, “Myology of the Chiroptera,” Phil. Trans. Roy. Soc., 1872).

Although, as above mentioned, the brain presents a low type of organization, yet probably no animals possess so delicate sense of touch as the Chiroptera. It is undoubtedly this perceptive power which enabled the individuals deprived of sight, hearing, and smell, in Spallanzani’s well-known experiments, to avoid the numerous threads hung across the rooms in which they were permitted to fly about. In the common Bats the tactile organs evidently exist, not only in the delicate vibrissae which spring from the sides of the muzzle, but also in the highly sensitive and widely extended integumentary structures entering into the formation of the wing-membranes and ear·conchs, while in many other species, notably in the tropical Rhinolophine and Phyllostomine Bats, peculiar foliaceous cutaneous expansions surrounding the nasal apertures or extending backwards behind them are superadded (vide infra). These structures, collectively known as the “nose-leaf” (whence the term il leaf-nosed Bats ”), have been shown by the present writer (who has traced their gradual development in different species) to be' made up partly of the extended and thickened marginal integument of the nostrils, and partly of the highly differentiated glandular eminences occupying the sides of the muzzle, in which, in all the common Bats, the vibrissae are implanted.

In all species of leaf-nosed Bats, and especially in th? Rhinolophidae, in which the nasal appendages reach their highest development, the superior maxillary division of the fifth nerve is of. remarkably large calibre. The nasal branch of this nerve, which is given off immediately beyond the infra-orbital foramen, is by far the largest portion, the palpebral and labial branches consisting of a few slender nerve fibres only. This branch passes forwards and upwards on the sides of the superior maxillary bone, but soon spreads out into numerous filaments which pass into the muscles and integument above, and into the base of the nose-leaf. The nerve supply of the nose-leaf is further considerably augmented by the large nasal branch of the ophthalmic division of the fifth nerve.

While the many foliations, elevations, and depressions which vary the form of the nose-leaf also greatly increase the sensory surface so abundantly supplied by the fifth nerve, and in rapid flight intensify the vibrations conveyed to it, the great number of sweat and oil glands which enter into its structure perform an important function, analogous to that of the glands of the auditory canal in relation to the membrana tympani, in maintaining its surface in a highly sensitive condition.

The nasal appendages of Chiroptera, then, may be regarded as performing the office of an organ of a very-exalted sense of touch standing in the same relation to the nasal branches of the sensory divisions of the fifth nerve as the aural apparatus to the auditory nerve; for, as the latter organ collects and transmits the waves of sound, so the former receives impressions arising from vibrations communicated to the air by approaching objects.

In no order of mammals is the ear-conch so greatly-developed or so variable in form; in most of the insectivorous species the ears are longer than the head, while in some, as in the common Long-eared Bat (Plecotus auritus), their length nearly equals that of the head and body. The form of the conch is very characteristic in each of the families; in most the tragus is remarkably large, in some extending nearly to the outer margin of the conch; its office appears to be to cause undulations in the waves of sound, and so intensify and prolong them. It is worthy of notice that in the only family of insectivorous Bats wanting the tragus, the Rhinolophidae, the auditory bullae osseae reach their greatest size, and the highly sensitive nasal appendages their highest development; also in the group Molossi the ear-conch is divided by a prominent keel; and the antitragus is remarkably large in those species in which the tragus is minute (see fig. 66, a). In the frugivorous Bats, as might be expected, the form of the car-conch is very simple, and but slightly variable throughout the species.

In all Bats the ears are extremely mobile, each moving independently at the will of the animal. This has been observed by the writer even in the frugivorous Pteropodidεe, in which the peculiar vibratory movements noticed by Mr Osburn in Artibeus perspicillatus may also be seen when the animals are alarmed.

The opening of the mouth is anterior in most species, but in many it is inferior, the extremity of the nose being more or less produced beyond the lower lip, so much so indeed in the small South-American species Rynchonycteris naso as to resemble that of the Shrews. The lips exhibit the greatest variety in form, which will be specially referred to under each family. The absence of a fringe of hairs is very characteristic of all fruit-eating Bats, and probably always distinguishes them from the insectivorous species, which they may resemble in the form of their teeth and in other respects.

The oesophagus is narrow in all species, and especially so in the sanguivorous Desmodontes. The stomach presents two principal types of structure, which correspond respectively to the two great divisions of the order, the Megaclιiroptera and the Microchiroptera ; in the former (with the exception of Harpyia) the pyloric extremity is more or less elongated and folded upon itself, in the latter it is simple, as in Insectivora vera; a third exceptional type is met with in the sanguivorous Desmodontes, where the left or cardiac extremity is greatly elongated, forming a 1 )ng narrow caecum-like appendage. The intestine is comparatively short, varying from one and a half to four times the length of the head and body, being longest in the frugivorous, shortest in the insectivorous species. In Rhinopoma microphyllum and Megaderma spasma only has a very small caecum been found. .

The liver is characterized by the great size of the left 1 itérai lobe", which occasionally equals half the size of the whole organ; the right and left lateral fissures are usually very deep; in Megachiroptera (Harpyia excepted) the Spigelian lobe is ill-defined or absent, and the caudate is generally very large, but in Microchiroptera, on the other hand, the Spigelian lobe is very large, while the caudate is small, in most species forming a ridge only. The gallbladder is generally well developed and attached to the right central lobe, except in Rhinolophidae, where it is connected with the left central.

In most species the hyoid bones are simple, consisting of a chain of slender, elongated, cylindrical bones connecting the small basi-hyoid with the cranium, while the pharynx is short, the larynx shallow with feebly developed vocal cords, and guarded by a short acutely-pointed epiglottis, which in some genera (Harpyia, Vampyrus, e.g.) is almost obsolete. In the Epomophori, however, we find a remarkable departure from the general type: the pharynx is long and very capacious, the aperture of the larynx far removed from the fauces, and, opposite to it, a canal, leading from the narial chambers, and extending along the back of the pharynx, opens; the laryngeal cavity is spacious and its walls are ossified: the hyoid bone is quite unconnected, except by muscle, with the cranium; the cerato-hyals and epi-hyals are cartilaginous and greatly expanded, entering into the formation of the walls of the pharynx, and, in the males of three species at least, supporting the orifices of a large pair of air-sacs communicating with the pharynx (see fig. 67).

In extent, peculiar modifications, and sensitiveness, the cutaneous system reaches its highest development in this order. As a sensory organ its chief modifications in connexion with the external ear, and with the nasal and labial appendages, have been described when referring to the nervous system. It remains therefore to consider its relative development as part cf the organs of flight.

The extent and shape of the volar membranes depend mainly on the form of the bones of the anterior extremities, and on the presence or absence of the tail. Certain modifications of these membranes, however, are met with, which evidently do not depend on the skeleton, but are related to the habits of the animals, and to the manner in which the wing is folded in repose.

The volar membranes consist of—(1) the “antebrachial membrane,” which extends from the point of the shoulder along the humerus and more or less of the forearm to the base of the thumb, the metacarpal bone of wflιich is partially or wholly included in it; (2) the “wing-membrane,”which is spread out between the greatly elongat¾β fingers, and extends along the sides of the body to the posterior extremities, generally reaching to the feet; and (3) the “interfemoral membrane,” the most variable of all, which is supported between the extremity of the body, the legs, and the calcanea (see fig. 65).

The antebrachial and wing membranes are most developed in those species which are fitted only for aerial locomotion, and which when at rest hang with the body enveloped in the wings; but in the family Embcdlomiridae, especially in the subfamily Molossinae (the species of which are, of all Bats, the best fitted for terrestrial progression), the antebrachial membrane is reduced to the smallest size, and is not developed along the forearm, leaving also the thumb quite free, and the wing-membrane is very narrow and folded in repose completely under the forearm. The relative development of the interfeιnoral membrane has been referred to above in describing the caudal vertebrae. Its small size in the frugivorous and sanguivorous species, which do not require it, to which, indeed, its presence would be actually injurious as impeding their motions when searching for food as they hang suspended by their feet, is easily understood. Odoriferous glands and pouches opening on the surface of the outer skin are developed in many species, but in most cases more so in males than in females, and so constitute very remarkable secondary sexual characters. They will be referred to when treating of the peculiarities of certain species. (See also the writer’s paper “On Secondary Sexual Characters in Chiroptera” Proc. Zool. Soc. Lond., 1873, pp. 241-252.)

Space does not admit of entering here upon a special description of the respiratory, circulatory, digestive, urinary, and generative organs, which will be found fully treated of in the works noted in the bibliography of the order below, and therefore with the above short account of the general structure of the species we proceed to consider their classification and geographical distribution.

The Chiroptera fall naturally into two subdivisions, which may be called suborders.

Suborder I. MEGΛCHIROPTERA.

Frugivorous Bats, generally of large size, having the crowns of the molar teeth smooth, marked with a longitudinal groove; with the bony palate continued behind the last molar narrowing slowly backwards; with three phalanges in the index finger, the third phalanx terminated generally by a claw; with the sides of the earconch forming a complete ring at the base; with the tail, when present, inferior to (not contained in) the interfemoral membrane; with the pyloric extremity of the stomach generally much elongated; and with the Spigelian lobe of the liver ill-defined or absent, while the caudate is well developed.

Frugivorous; limited to the tropical and subtropical parts of the Eastern Hemisphere.

Family Pteropodidae.

The characters of the single family are those of the suborder.

Epomophorus, i ⅜ (or ⅛), c ⅜, pm ⅜, m ⅜; tail very short or none, when present quite free from the interfemoral membrane; second finger with a claw; premaxillary bones united in front. The six species include some of the most remarkable forms of fruiteating Bats. They are strictly limited to the African continent sou⅛, of the Sahara, and are readily distinguished by their remarkably large and long head and very expansible, often peculiarly folded, lips, and by the invariable white tuft of hair which adorns the margins of the ears; most of the species also are provided with peculiar glandular pouches, situated in the integument of the side of the neck near the point of the shoulder. These pouches are rudimentary or quite absent in females, thus presenting an interesting secondary sexual character. In the males they are lined with a glandular membrane, from which long coarse yellowish hairs arise, and, projecting from the mouth of the pouches, form conspicuous epaulet-like tufts on the shoulders, hence the generic name. Another and even still more remarkable secondary sexual character has been recently discovered by the writer in the males of E. franqueti, comphιs, pusillus, and monstrosus. This consists in the presence of a pair of large air-sacs extending outwards on each side from the pharynx beneath the integument of the neck, in the position shown in fig. 67. These sacs are evidently capable of being greatly distended at the will of the animal, and their inflation probably occurs under the same circumstances that the wattles of male gallinaceous birds swell up, namely, when engaged in courting the females. Other remarkable conditions in which these Bats appear to differ from all other species, as in the peculiar structure of the hyoid bones and larynx, may be found described in detail in the writer’s paper in the Proceedings of the Zoological Society for June 1881. These Bats appear to live principally on figs, the juicy contents of which their voluminous lips and capacious mouths enable them to swallow without loss.

Pteropus, i f, c ⅜, pm ⅜, m ⅜, with forty-one species, includes more than half the Pteropodidae. All are of large size, and the absence of a tail, the long poin ted muzzle, and the woolly fur covering the neck render their recognition easy. They are the “Flying Foxes” of Europeans in India, and one of the species, Pt. edulis, inhabiting Java, measures 5 feet across the fully extended wings, and is the largest known species of the order. The species resemble one another closely in dentition, and are mainly distinguished by the form of the ears and quality of the fur. Pt. scapulal·us, from north-east Australia, approaches the species of thé second section of the family, the Macroglossi, in the remarkable narrowness of its molars and premolars.

The geographical range of the genus is very peculiar, extending from Madagascar and its islands through the Seychelles to India, Ceylon, Burmah, the Malay Archipelago, southern Japan, New Guinea, Australia, and* Polynesia (except the Sandwich Islands, Ellice's Group, Gilbert’s Group, Tokelau, and the Low Archipelago). Of the islands inhabited some are very small and remote from any continent, such as Savage Island in the South Pacific, and Kodriguez in the Indian Ocean. Although two species inhabit the Comoro Islands, which are scarcely 200 miles from the African coast, not a single species is found in Africa; yet in India, separated by thousands of miles of almost unbroken ocean, a species exceedingly closely allied to the common Madagascar“Flying Fox” isabundant. The Malay Archipelago and Australia are their headquarters, and in some places they occur in countless multitudes. Mr Macgillivray remarks of Pt. conspicillatus :— “On the wooded slope of a hill oh Fitzroy Island I one day fell in with this Bat in prodigious numbers, looking while flying in the bright sunshine (so unusual for a nocturnal animal) like a large flock of rooks. On close approach a strong musky odour became apparent, and a loud incessant chattering was heard. Many of the branches were bending under their load of Bats, some in a state of inactivity, suspended by their hind claws, others scrambling along among the boughs, and taking to wing when disturbed.” Cynonycteris, dentition as in Pteropus, but with a short tail, and the fur of the back of the neck not differing from that of the back, with nine species, extends into Africa, but has not been recorded from Australia or Polynesia; otherwise its distribution accords with that of Pteropus. C. aegyptiaca inhabits the chambers of the Great Pyramid and other deserted buildings in Egypt, and is probably the species so generally figured in Egyptian frescos. Boneia, with one species, B. bidens, from Borneo, differs from Cynonycteris in having two upper incisors only.

Cynopterus, i ∣ or ∣, c f, pm ⅜, m ⅜, muzzle shorter and grooved like Pteropus in front, tail and fur as in Cynonycteris, with seven species, is almost limited to the Oriental region. C. marginatus is very common in India, and extremely destructive to ripe fruit of every description. To a specimen of this Bat obtained by the writer at Calcutta uninjured was given a ripe banana, which, with the skin removed, weighed exactly 2 ounces. The animal immediately, as if famished with hunger, fell upon the fruit, seizing it between the thumbs and the index fingers, and took large mouthfuls out of it, opening the mouth to the fullest extent with extreme voracity. In the space of three hours the whole fruit was consumed. Next morning the Bat was killed, and found to weigh one ounce, half the weight of the food eaten in three hours. Indeed the animal when eating seemed to be a kind of living mill, the food passing from it almost as fast as devoured, and apparently unaltered,eating being, as it were, performed only for the pleasure of eating.

Harpyia, i ⅜, c ⅛, , . pm⅛, m I, premaxillary bones well-developed and united in front, facial bones much elevated above the margin of the jaw, nostrils tubular, body and limbs as in Cynopterus, includes two species of very remarkable physiognomy (as may be seen from fig. 70), limited to the Austro-Malayan subregion.

Cephalotes, i f, c ⅛, pm ⅜, m ⅜, premaxillary bones not united in front, nostrils simple, muzzle short, index finger without a claw, tail short, includes two species, having the same distribution as those of Harpyia ; in both the wing-membrane arises from the centre line of the back, to which it is attached by a longitudinal very thin process of the integument; the wings are quite naked, but the back covered by them is well clothed with hair.

Notopteris, i γ, c f, pm ⅜, m ⅜, index finger without a claw, wings from the spine, tail long. With this genus we enter the second division of the family, the Macroglossi, which have the facial part of the skull much produced, the molar teeth narrow, and scarcely raised above the gum, and the tongue exceedingly long, attenuated in the anterior third, and armed with long recurved papillae near the tip. The single representative of the genus, N. macdonaldii, inhabits the Fiji Islands, Aneiteum Island, and New Guinea. It is at once distinguished from all other Bats of this family by the remarkable length of its tail, which is nearly as long as the forearm.

Eonycteris, i ⅜, c f, pm ⅜, m ⅜, is also represented by a single species, E. spclaea, from the Farm Caves, Moulmein, Burmah, which has somewhat the appearance of a Cynonycteris, but the absence of a claw in the index finger and the presence of the characteristic tongue and teeth at once distinguish it.

Macroglossτιs and Melonycteris, each with a single species, are closely allied; the index finger in both has a claw, but the number of the teeth is the same as in Eonycteris. Macroglossus minimus is the smallest known species of the suborder; it is much smaller than the common Serotine Bat of Europe, and its forearm is scarcely longer than that of the Long-eared Bat. It is nearly as common in certain parts of India as Cynopterus marginatus (compared with which it is proportionally equally destructive to fruit), and extends eastward through the Malay Archipelago as far as New Ireland, where it is associated with Melonycteris melanops, distinguished from it by its larger size and by the total absence of the tail.

Suborder II. MICROCHIROPTERA.

Insectivorous (rarely frugivorous or sanguivorous) Bats, of comparatively small size, having the crowns of the molar teeth acutely tuberculated, marked by transverse grooves, with the bony palate narrowing abruptly, not continued backwards laterally behind the last molar; with one rudimentary phalanx (rarely two phalanges or none) in the index finger, which is never terminated by a claw; with the outer and inner sides of the ear-conch commencing inferiorly from separate points of origin; with the tail, when present, contained in the interfemoral membrane, or appearing upon its upper surface; with a simple stomach (except in Desmodontes) ; and with the Spigelian lobe of the liver very large, the caudate lobe generally small. Inhabiting the tropical and temperate regions of both hemispheres.

The Bats included in this suborder are mainly insectivorous, though some are frugivorous, and two species are known to be sanguivorous. They fall into five natural families, which may be arranged in two groups or alliances as follows :— [table]

II. lad perforating the interfemoral membrane, and appearing on its upper surface, or produced considerably beyond the truncated membrane; the middle pair of upper incisors generally large and close together. II. Emballonurine Alliance. [table]

I. Vespertilionine Alliance. Family Vespertilionidae.

In the above synopsis of the families of Microchiroptera the Vespertilionidae take the centraj position; and this is, indeed, the place really occupied by them in the suborder. This family includes the common simple-faced Bats of all countries, of which the well-known Pipistrelle and the Whiskered Bat (Vespertilio mystacinus) may be taken as familiar types, and its species number about 150, considerably more than one-third the total number of the known species of Chiroptera, estimated at slightly over 400 (see Introd, to Dobson’s Gated. Chiropt. Brit. Mus., 1878). Besides the characters of the family given in the synopsis, it may be added that the skull is of moderate size, the nasal and frontal bones not much extended laterally or vertically, nor furrowed by deep depressions; the number of incisors varies from ∣ to ⅜, rarely (in Antrozous only) ⅜, premolars ⅜ or ⅜ or ⅜, rarely (in Vesperugo noctiυagans of North America) the upper incisors are small, separated by a wide space in the centre, and placed in pairs or singly near the canines; the molars are well-developed, with acute W-shaped cusps. The family is distributed over the temperate and tropical regions of both hemispheres. The genera may be conveniently divided into four groups :— Plccoti, Vespertiliones, Miniopteri, and Thyropteri.

In the Plecoti, of which the common Long-eared Bat (Plecotus auritus') is the type, the crown of the head is but slightly raised above the face-line, the upper incisors are close to the canines, and the nostrils are margined behind by grooves on the upper surface of the muzzle, or by rudimentary nose-leaves; the ears also are generally very large and united. Of the five genera, Plccotus, i ⅜, pm ⅜, has two species :—one the common Long-eared European Bat referred to above; the other, P. macrotis, restricted to North America, is distinguished by the great size of the glandular, prominences of the sides of the muzzle, which meet in the centre above and behind the nostrils. Synotus, i ⅜, pm ⅜, distinguished by dentition and by the outer margin of the ear being carried forwards above the mouth and in front of the eye, includes the European Barbastelle Bat, S. barbastellus, and S. darjel ingensis from the Himalaya. Otonycteris, i ⅜, pm ⅜, connecting this group with the Vespertiliones through the tropical Scotophili, is represented by a single species, 0. hemprichii, from North Africa and the Himalaya. The next two genera are distinguished by the presence of a rudimentary nose-leaf:— Nyctophihιs, i ⅜, pm ⅛, with one species, N. timoriensis, from the Australian region; and Antrozous, i ⅜, pm ⅜, distinguished from all the family besides by having but two lower incisors, and from other Plecoti by the separate ears; the single species, A. pallidus, inhabits California.

The group Vespertiliones, with eight genera, includes nine-tenths of the species. Of these one-third are contained in the genus Vesperugo, which is divisible into six subgenera according to the number of premolars and incisors; the latter vary from ⅜ to ⅜ in the subgenera Scotozous and Rhogeëssa, and the premolars from ∣ to ⅜ (in the subgenus Lasionyctcris ⅜). The Bats of this genus are generally easily distinguished by their comparatively thickly formed bodies, by their flat broad heads and obtuse muzzles, by their short, broad, and triangular, obtusely-pointed ears, by their obtuse and usually slightly incurved tragus, by their short legs, and by the presence in most species of a well-developed post-calcaneal lobule. This lobule (which is supported by a cartilaginous process derived from the calcaneum) may act as a kind of adhesive disk in securing the animal’s grasp when climbing over smooth surfaces. Vesperugo probably contains the greatest number of individuals among the genera of Chiroptera, and, with the exception of Vespertilio, its species have also the widest geographical range, being in fact cosmopolitan; and one of the species, the well-known Serotine, V. ( Vesperus) serotinus, is remarkable as the only species of Bat known to inhabit both the Old and the New World; one, V. borealis, has been found close to the limits of the Arctic Circle, and another, V. magellanicus, inhabits the cold and desolate shores of the Straits of Magellan, doubtless the Bat referred to by Mr Darwin in the Naturalist's Voyage. Chalinolobus agrees with Vesperugo in the dental formula, but is readily distinguished by the presence of a well-defined lobe projecting near the angle of the mouth from the lower-lip, and by the unicuspidate upper inner incisors. The species fall into two subgenera:— Chalinolobus, pm ⅜, with C. tuberculatus from New Zealand, Tasmania, and Australia, and three other species from Australia; and Glauconycteris, pm ⅜, limited to southern and equatorial Africa, with G. argentatus and two other species, the Bats of this subgenus being especially remarkable for their peculiarly thin membranes traversed by very distinct reticulations and parallel lines. Scotophilus, i ⅜, pm ⅜, includes eight species, restricted to the tropical and subtropical regions of the eastern hemisphere, though widely distributed within these limits. The Bats of this genus, though difficult to define, and approaching certain of those of Vesperugo in. many points, are distinguished especially by the single pair of unicuspidate upper incisors separated by a wide space and placed close to the canines, by the small transverse first lower premolar crushed in between the canine and second premolar, and, generally, by their conical nearly naked muzzles and remarkably thick leathery membranes. Sc. t&m-minckii is probably the commonest species of Bat in India, and appears often on the wing even before the sun has touched the horizon, especially when the white ants are swarming, feeding eagerly upon them as they rise in the air. Sc. gigas, from equatorial Africa, with the forearm 3 ’ 4 inches, is by far th⅛ largest species. Nycticejus, with the same dental formula as Scotophilus, is distinguished by the first lower premolar not being crushed in between the adjoining teeth, and by the comparatively much greater size of the last upper molar. It includes only the common North American species N. crepuscularis, a small Bat scarcely larger than the Pipistrelle. Atalapha, i ⅜, pm ⅜ or ⅜, with five species, is also limited to the New World. The Bats of this genus are generally characterized by the interfemoral membrane being more or less covered with hair (in the two commonest species, A. noveboracensis and A. cinerea, wholly thickly covered), and by the peculiar form of the tragus, which is expanded above and abruptly curved inwards. In these species, which have two upper premolars, the first is extremely small and quite internal to the tooth-row. The genus Harpyiocephalus, i ⅞, pm ⅞, includes eight very remarkable small species, distinguished at once by their prominent tube-like nostrils and hairy interfemoral membrane. H. suillus from Java and neighbouring islands is the best-known species, and another closely allied, II. hilgendorfi, has been described by Professor Peters from Japan. The remaining six species are known only from the Himalaya and Tibet. All appear to be restricted to the hill tracts of the countries in which they are found. Next to Vesperugo, the genus Vespertilio, i ⅜, pm f, includes by far the largest number of species, amounting to forty-three; it has, however, rather a wider geographical distribution in both hemispheres, one species at least being recorded from the Navigators’ Islands. The species are easily recognized by the peculiar character of the pairs of upper incisors on each side, the cusps of which diverge from each other, by the large number of premolars, of which the second upper is always very small, and by the oval elongated ear and narrow attenuated tragus. Keriυoula, with the same dental formula as Vespertilio, is easily distinguished by the parallel upper incisors, and by the comparatively large size of the second upper premolar. Ten species have been described from the

Ethiopian and Oriental regions, of which K. picta, from India and the Indo-Malayan subregion, is the best-known, being well characterized by its brilliantly coloured orange fur and conspicuously marked membrane, which are variegated with orange and black. The genus includes the most delicately formed and most truly insectivorous, tropical, forest-haunting Bats, which appear to stand as regards the species of Vespertilio ina position similar to that occupied by Chalinolobus with respect to Vesperugo.

The next group, Miniopteri, includes two genera, Natalus and Miniopterus, characterized by the great elevation of the crown of the head above the face-line, and by the upper incisors being separated from the canines and also in front. Natalus, with the same dental formula and general external form as Kerivoula, is distinguished by the short triangular tragus, and by the characters of the group enumerated above. It includes three species, all restricted to South and Central America and the West Indies; the head of one, N. micropus, lately described by the present writer, is shown in fig. 73. Miniopterus, i ⅜, pm ⅜, at once distinguished by the shortness of the first phalanx of the middle finger, and by the great length of the tail, which is wholly contained within the interfemoral membrane, includes four species, restricted to the eastern hemisphere. Of these the best-known, Μ. schreibcrsii, is very widely distributed, being found almost everywhere throughout the tropical and warmer temperate regions of the eastern hemisphere, specimens from Germany, Madagascar, Japan, and Australia differing in no appreciable respect.

The last group, Thyropteri, includes also two genera, distinguished not only by the presence of an additional osseous phalanx in the middle finger and an equal number of phalanges in the toes, but also by peculiar accessory clinging organs attached to the extremities. In Thyroptera tricolor, i⅞, pm ⅜, from Brazil, these organs have the appearance of small, circular, pedunculated, hollow disks (fig. 74), resembling in miniature the sucking cups of cuttle-fishes, and attached to the inferior surfaces of the thumbs and soles of the feet, with which the animal is enabled to maintain its hold when creeping over smooth vertical surfaces (for an account of the minute anatomy of these clinging organs see the writer’s paper in the Proc. Zool. Soc., 1876, pp. 531-34). In Myxopoda aurita from Madagascar (type of the second genus), with the same dental formula, but differing much in the characters of the teeth and in the form of the ears, the whole inferior surface of the thumb supports a large sessile horse-shoe-shaped adhesive pad, with the circular margin directed forwards and notched along its edge, and a smaller pad occupies part of the sole of the foot.

Family Nycteridae.

This small family, defined in the synopsis above, includes only two genera of Bats of very peculiar aspect, limited to the tropical and subtropical parts of the eastern hemisphere.

Megaderma, i S), pm ⅞ or ⅜, with five species, is distinguished l·y the absence of upper incisors, by the cylindrical narrow muzzle surmounted by an erect naked cutaneous process (the nose-leaf), the base of which conceals the nasal orifices, by the immense connate ears with large bifid tragi, and by the great extent of the interfemoral membrane, in the base of which the very short tail is concealed. Μ. gigas, from central Queensland (forearm 4 ‘2 inches), is not only the largest species of the genus but also of the suborder. Μ. lyra, common in India (forearm 27 inches), has been caught in the act of sucking the blood, while flying, from a small species of Vesperugo, which it afterwards devoured (see Dobson’s Monograph of the Asiatic Chiroptera, p 77). so that it is probable that the Bats of this genus do not confine themselves to insect prey alone, but also feed, when they can, upon the smaller species of Bats and other small mammals.

Nycteris, i j, pm ∣, with seven species, differs so much from Megaderma that it may be considered the type of a separate subfamily. As in that genus, the frontal bones are deeply hollowed out and expanded laterally, the muzzle presents a similar cylindrical form, and the lower jaw also projects, but the single elevated nose· leaf is absent, and instead of it the face is marked by a deep longitudinal sharp-edged groove extending from the nostrils (which are on the upper surface of the muzzle near its extremity) to the low band connecting the bases of the large ears; the sides of this depression are margined as far back as the eyes by small horizontal cutaneous appendages. All the species resemble one another closely, and are mainly distinguished by the form of the tragus, and the size and relative position of the second lower premolar. With the exception of N. javanica, all the species are limited to the Ethiopian region.

Family Ehinolophidae.

In all the species of this family the nasal appendages are highly developed, and surround on all sides the nasal apertures, which are situated in a depression on the upper surface of the muzzle; the ears are large and generally separate, without trace of a tragus; the premaxillary bones are rudimentary, are suspended from the nasal cartilages, and support a pair of very small incisors; the molars have acute W-shaped cusps; the skull is large, and the nasal bones which support the large nasal cutaneous appendages are much expanded vertically and laterally; in females a pair of teatlike appendages are found in front of the pubis; and the tail is long and produced to the posterior margin of the interfemoral membrane. The family is found in the temperate and tropical parts of the eastern hemisphere.

From whatever point of view the Ehinolophidae may be considered, 1hey are evidently the most highly organized of insectivorous Bats. In them the osseous and cutaneous systems reach the most perfect development. Compared with theirs the bones of the extremities and the volar membranes of other Bats appear coarsely formed, and even their teeth seem less perfectly fitted to crush the hard bodies of insects. The very complicated nasal appendages, which evidently act as delicate organs of special perception (vide supra), here reach their highest development, and the differences in their form afford valuable characters in the discrimination of the species, which resemble one another very closely in dentition and in the colour of the fur.

Subfamily I. Rhinolophinae.—First toe with two, other toes with three phalanges each; ilio-ρectineal spine not connected by hone with the antero-inferior surface of the ilium.

Ehinolophus, i ⅜, c f, pm f, m ⅜, nose-leaf with a central process behind and between the nasal orifices, posterior extremity lanceolate, antitragus large, includes twenty-four species. E. hectics, forearm 3 inches, is the largest species, inhabiting elevated hill tracts in India and Malayana; E. hipposideros of Europe, extending into south England and Ireland, forearm 1 ‘5 inches, is one of the smallest; and E.ferrum-cquinum, forearm 23 inches, represents the average size of the s pecies, which are mainly distinguished from one another by the form of the nose-leaf. The last-named species extends from England to Japan, and southward to the Cape of Good Hope.

Subfamily II. Phyllorhininae.— Toes equal, of two phalanges each; ilio-pectineal spine united by a bony isthmus with a process derived from the antero-inferior surface of the ilium.

Phyllorhina, with twenty-two species, and Ehinonycteris, Triaenops, and Codops, with one each, represent this subfamily. Phyllorhina, i ⅛, c I, pm ⅜ or ⅜, m ⅜, differs from Ehinolophus in the form of the nose-leaf, which is not lanceolate behind (see fig. 76), and is unprovided with a central process covering the nostrils; the largest species, Ph. armigera, appears to be the most northerly, having been taken at Amoy in China, and in the Himalaya at an elevation of 5500 feet. Many are provided with a peculiar frontal sac behind the nose-leaf, rudimentary in females (see fig. 67), which the animal can evert at pleasure; the sides of this sac secrete a waxy substance, and its extremity supports a pencil of straight hairs. Ehinonycteris, represented by E. aurantia from Australia, and Triaenops, by T. persicus, from Persia and eastern Africa, are closely allied genera; the latter species is characterized by the very remarkable form of its nasal appendages and ears, and by the presence of a peculiar osseous projection from the proximal extremity of the second phalanx of the fourth finger. Codops (C. frithii), from the Bengal Sunderbunds, Java, and Siam (in the roof of the great pagoda at Laos), is distinguished, not only by the very peculiar form of its nose-leaf, but also by the great length of the metacarpal bone of the index finger, as well as by the shortness of the calcanea and interfemoral membrane.

II. Emballonurine Alliance. Family Emballonukidae.

The second group of families (as defined above) into which the Microchiroptera may be divided includes the Emballonuridst and Phyllostomidae. The former is represented by thirteen genera, including sixty-five species. The Emballonuridae are generally easily distinguished by the peculiar form of the muzzle, which is obliquely truncated, the nostrils projecting more or less in front beyond the lower lip, by the first phalanx of the middle finger being folded in repose forwards on the upper surface of the metacarpal bone, by the tail, which either perforates the interfemoral membrane or is produced far beyond it, and by the upper incisors, which are generally a single pair separated from the canines and also in front. They are cosmopolitan like the Vesper- tilionidae, but rarely extend north or south of the thirtieth parallel of latitude.

Subfamily I. Emballonurinae.—Tail slender, perforating the interfemoral membrane, and appearing upon its upper surface, or terminating in it; legs long, fibulae very slender; upper incisors weak.

Group I. Furiae. — Tail terminating in the interfemoral membrane; crown of the head greatly elevated above the face-line; thumb and first phalanx of the middle finger very short; i ∣, c }, pm ⅜, m ⅜ .

Two genera, Furia and Amorphochilus, each including one species of very peculiar aspect, the latter distinguished from the former by the widely separated nostrils and great extension backwards of the bony palate. Habitat South America.

Group II. Emballonurae. — Part of the tail included in the basal half of the interfemoral membrane, the remaining part passing through and appearing upon its upper surface; crown of the head slightly elevated; thumb and first phalanx of the middle finger moderately long; pm⅜. With five genera.

Emballonura, i ⅜, extremity cf the muzzle more or less produced beyond the lower lip, forehead flat, contains five species, inhabiting islands from Madagascar through the Malay Archipelago to the Navigators’ Islands. Coleüra, i ⅜, extremity of the muzzle broad, forehead concave, has two species from east Africa and the Seychelles Islands. Ehynchonycteris is distinguished from Coleüra by the much produced extremity of the muzzle; the single species, E. naso, from Central and South America, is very common in the vicinity of streams throughout the tropical parts of these countries. It is usually found during the day resting on the vertical faces of rocks, or on the trunks of trees growing out over the water, and, owing to the peculiar greyish colour of the fur covering the body and growing in small tufts from the antebrachial membrane, counterfeiting the weathered surfaces of the rocks and the bark of the trees, easily escapes notice. As the shades of evening approach it appears early on the wing, flying close to the surface of the water, and seizing the minute insects that hover over it. Saccoptcryx, i ⅜, antebrachial membrane with a pouch opening on its upper surface, contains six species from Central and South America; the wing-sac varies in position in different species. It is developed only in the male; in the female it is quite rudimentary. In the adult males of the different species a valvular longitudinal opening is found on the upper surface of the membrane. This opening leads into a small pouch (in some species large enough to hold a pea), the interior of which is lined with a glandular membrane secreting an unctuous substance of a reddish colour with a strong ammoniacal odour. The presence of this sac in males only indicates that it is a secondary sexual character analogous to the shoulder pouches of Epomophorus, the frontal sacs of Phyllorhina, kc.

The next genus Taphozous, including ten species, inhabiting the tropical and subtropical parts of all the eastern hemisphere except Polynesia, forms the second section of this group, distinguished by its cartilaginous premaxillaries, deciduous pair of upper incisors, and by the presence of four lower incisors only. Most of the species have a peculiar glandular sac (see fig. 80) placed between the angles of the lower jaw, a sexual character; for, while always more developed in males than in females, in some species, although distinct in the male, it is quite absent in the female. An open gular sac is wanting in both sexes in T. melanopogon, but about its usual position the openings of small pores may be seen, the secretion exuding from which probably causes the hairs to grow very long, forming the black beard found in many male specimens of this species.

Group III. Dicliduri.— This is represented by a single genus, Diclidurus, including two species. D. albus, from Central and South America, i ⅜, c ⅜, pm ⅜, m f, resembles the species of Taphozous in the form of the head and ears, but, besides other characters, differs from all other Bats in possessing a peculiar pouch, opening on the centre of the inferior surface of the interfemoral membrane; the extremity of the tail enters this, and perforates its fundus.

Group IV. Noctiliones.— This also is represented by a single genus and two species, Noctilio leporinus and N. dorsatus, i f, pm ⅜, from Central and South America. The group connects the family Emballonuridae with the Phyllostomidae, possessing character's common to both, but also so many remarkable special peculiarities as almost to warrant the formation of a separate family for its reception. The type, N. leporimιs of Linnaeus, is a Bat of very curious aspect, with strangely folded lips, erect cutaneous processes on the chin, and enormous feet and claws. The two middle incisors are close together, and so large as to conceal the small outer ones, while in the lower jaw there are but two small incisors. This apparent resemblance to a Rodent actually led the great naturalist to remove this species from the Bats and place it in his order Glires or

Rodents. Similarly the next group Rhinopomata, represented by a single species, R. microphyllum, might also be elevated into the rank of a family, for it is very difficult to determine its exact affinities, a kind of cross relationship attaching it to the Nycteridae on the one hand and to this family, in which it is here placed provisionally, on the other. This curious species, distinguished from all other Microchiroptera as well by the presence of two phalanges in the index finger as by its remarkably long and slender tail projecting far beyond the narrow interfemoral membrane, inhabits the subterranean tombs in Egypt and deserted buildings generally from north-east Africa to Burmah.

Subfamily II. Molossiuae. —Tail thick, produced far beyond the posterior margin of the interfemoral membrane (except in Mystacina) ; legs short and strong, with well-developed fibulae; upper incisors strong. This subfamily includes all the species of Emballonuridae with short and strong legs and broad feet—whereof the first toe (and in most species the fifth also) is much thicker than the others, and furnished with long curved hairs,—with well-developed callosities at the base of the thumbs, and with a single pair of large upper incisors occupying the centre of the space between the canines. In all the species the feet are free from the wingmembrane, which folds up very perfectly under the forearm and legs; the interfemoral membrane is retractile, being movable backwards and forwards along the tail, and this power of varying its superficial extent must confer upon these Bats great dexterity in quickly changing the direction of their flight, as when obliged to double in pursuing their swiftly-flying insect prey, which their extremely expansible lips evidently enable them to secure with ease.

Group I. Molossi. — Tail produced beyond the posterior margin of the interfemoral membrane.

Cheiromeles, i J, c ⅛, pm ⅜, m ∣, hallux much larger than the other toes and separable from them, ears separate, is represented by a single species, G. torquatus, of large size (forearm 3'1 inches) and very peculiar aspect, inhabiting the Indo-Malayan subregion. This species is nearly naked, a collar only of thinly spread hairs half surrounding the neck, and is further remarkable for its enormous throat sac and curious nursing pouches. The former consists of^a great semicircular fold of skinforminga deep pouch roundthe neck beneath, concealing the orifices of large subcutaneous pectoral glands which discharge an oily fluid oζ insufferably offensive smell. The nursing pouch is formed on each side by an extension of a fold of skin from the side of the body to the inferior surfaces of the humerus and femur. In the anterior part of this pouch the mamma is placed. For figures of these throat sacs and notes on the use of the nursing pouches see Catal. Chiroptera, p. 406, pl. xxi.

Molossus, i f or ⅜, pm ⅜ or f, upper incisors close together in front, with ten species, is restricted to the tropical and subtropical regions of the New World. The woodcut of Μ. glaucinus (fig. 82) exhibits the general physiognomy of the Bats of this genus. Μ. obscurus, a small species, is very common in tropical America. It inhabits the hollow trunks of palms and other trees, and also the roofs of houses. The males and females live apart (as, indeed, appears to be the case in most if not in all species of Bats). In the hollow trunk of a palm two colonies were discovered, one consisting of from 150 to 200 individuals, exclusively males, while the other was composed of females with a male here and there among them.

Nyctinomus, i ⅜ or ⅜, pm ⅜ or ⅛, upper incisors separate in front, includes twenty-one species, inhabiting the tropical and subtropical parts of both hemispheres. The lips of the Bats of this genus are even more expansible than in Molossus, in many of the species (as in the woodcut of the head of N^. macrotis, fig. 83) showing vertical wrinkles. Μ. cestonii, one of the largest species, alone extends into Europe, and has been taken as far north as Switzerland. N. johorensis, from the Malay Peninsula, is remarkable from the extraordinary form of its ears. A r . brasiliensis is nearly as common as M. obscurus in tropical America, and extends farther north (California) and south than that species.

Group II. Mystacinae. — Tail perforating the interfemoral membrane, and appearing upon its upper surface.

This includes a single genus and species, Mystadna tuberculata, a very peculiar form restricted to New Zealand, where, with Ghalinolobus tuberculatus, it represents the whole indigenous mammalian fauna of the islands. There are three distinct phalanges in the middle finger; the greater part of the wing-membrane is exceedingly thin, but a narrow portion along the forearm, the sides of the body, and the legs is remarkably thick and leathery; beneath this thickened portion the wings are folded, and it is evidently analogous to the thickened part of the anterior wings in hemipterous insects and to the elytra of the Coleoptera. With the wings thus encased, this species is the most quadrupedal of Bats. Other peculiarities of structure are found in the remarkable form of the claws of the thumbs and toes, which have each a small talon projecting from its concave surface near the base, also in the sole of the foot and inferior surface of the leg, as shown in fig. 84. The plantar surface, including the toes, is covered with soft and very lax integument deeply wrinkled, and each toe is marked by a central longitudinal groove with short grooves at right angles to it, as in the genus Hemidactylus {Geckotidae). The lax wrinkled integument is continued along the inferior flattened surface of the ankle and leg. These peculiarities appear to be related to climbing habits in the species. See the writer’s remarks in Proc. Zool. Soc., 1876, p. 488.

Family Phyllostomid.e.

The Bats included in this family are readily distinguished by the presence of a well-developed third phalanx in the middle finger, associated either with distinct cutaneous nasal appendages, or with well-developed central upper incisors, or with both. Unlike the Rhinolophidae, their eyes are generally large, and the tragus well developed, maintaining almost the same form throughout the species, however much the outer parts of the body may vary. Their fur is. of a dull colour, and the face and back (in the Stcnodermata especially) are often marked with white streaks, as in the Pteropodidae, of which they take the place in the western hemisphere. À few species, probably all those with the tail and interfemoral membrane well-developed, feed principally on insects, while the greater number of the species of the groups Vampyri and Glossophagae appear to live on a mixed diet of insects and fruits, and the Desmodontes, of which two species only are known, are true bloodsuckers, and have their teeth and intestinal tract specially modified in accordance with their habits. Limited to the tropical and subtropical parts of Central and South America.

Subfamily 1. Lobostominae.—Nostrils opening by simple apertures at the extremity of the muzzιe in front, not margined by a distinct nose-leaf; chin with expanded, leaf-like appendages.

It includes two genera. In Chilonycteris (six species) the crown of the head is moderately elevated above the face-line, and the basicranial axis is almost in the same plane as the facial, while in Mormops the crown of the head is greatly elevated above, the faceline, and the basicranial axis is almost at right angles to the facial; i ⅜, pm § in both genera. The latter genus contains two species, which, in their very peculiar physiognomy, are probably the most remarkable among the many strange forms exhibited by the different species of this order.

Subfamily 2. Phyllostominae.—Nostrils opening on the upper surface of the muzzle, the nasal apertures more or less surrounded or margined by well-developed cutaneous appendages, forming a distinct nose-leaf; chin with warts.

Group I. Vampyri.— Muzzle long and narrow in front, the distance between the eyes generally less than, rarely equal to, the distance from the eye to the extremity of the muzzleq nose-leaf well-developed, horse-shoe-shaped in front, lanceolate behind; interfemoral membrane well-developed; tail generally distinct, rarely absent; inner margin of the lips not fringed; i ⅜ or ∣, pm ⅝ or ⅜; molars with W-shaped cusps, usually well-developed.

Nearly all the species of Vampyri appear to be insectivorous, so that the term applied to this group cannot be considered indicative of their habits. A few, if not all, probably supplement their insect diet with fruit. Vampyrus spectrum (the largest Bat in the New World, forearm 4 ’ 2 inches) is said to be wholly frugivorous, and. Macrotus waterhousii appears to prey occasionally on small species of Bats, like Megaderma lyra oΓ the eastern hemisphere, which it resembles in many respects.

The species may be divided into two sections, according as the tail is produced to the hinder margin of the interfemoral membrane or perforates it and appears upon its upper surface. Those included in the first section fall into three genera, Lonchorhina, Macrotus, and Macrophyllum, the first-named including a very remarkable species, I.. aurita, with an extraordinary long nose-leaf and peculiarly large ears and tragi. In the second section are included the genera Vampyrus, Lopho-stoma, Schizostoma, Trachyops, Phylloderma, Phyllostoma, Tylostoma, Mimon, Carollia, and Rhinophylla, all, with the exception of the last, distinguished from one another chiefly by the form, of the skull and the presence or absence of the second lower premolar; Trachyops, Phylloderma, and the three last-named genera are each represented by a single species. Phyllostoma hastatum, forearm 3 - 2 inches, next in point of size to Vampyrus spectrum, is a well-known species in South America; Ph. clongatum (see fig. 86) differs in its smaller size and much larger nose-leaf. Carollia breυicauda, a small species, is generally found represented in collections, and externally so closely resembles Glossophaga soricina (of the next group) that it has often been confounded with that species. It forms a connecting link between this group and the next Khinophylla pumilio, forearm 1 '25 inches, tail none, is the smallest known species of the family; it is further distinguished by the narrowness of its molars, which do not form W-shaped cusps, and by the very small size of the last upper molar, characters connecting it, and consequently the group, with the Stcnodermata.

Group II. Glossophagae. — Muzzle long and narrow; tongue remarkably long and extensible, much attenuated towards the tip, and beset with very long filiform recurved papillae; lower lip with a wide groove above, and in front margined by small warts; noseleaf small; tail short or none; i ⅜, pm ⅜ or ⅜ or ⅜, m ⅜ or ⅜ or ⅜; teeth very narrow; molars with narrow W-shaped cusps, sometimes indistinct or absent; lower incisors very small or deciduous.

The ten species included in this group represent seven genera, which are distinguished principally by differences in the form and number of the teeth, and by the presence or absence of the zygomatic arches. The form and position or the upper incisors are extremely variable. In Glossophaga and Phyllonycteris the upper incisors form, as in the Vampyri, a continuous row between the canines; in Monophylla and Ischnoglossa they are separated into pairs by a narrow interval in front; while in Lonchoglossa, Glossonycteris, and Choeronycteris they are widely separated and placed in pairs near the canines; in the first four genera the lower incisors are present (at least up to a certain age), in the last three they are deciduous even in youth. The zygomatic arch is wanting in Phyllonycteris, Glossonycteris, and Choeronycteris.

The typical species is Glossophaga soricina, which so closely resembles Carollia brevicauda, both in external form and dentition, that it has frequently been confounded with it. Its long fibrillated tongue (which it possesses in common with other species of the group) led Spix to describe it as a very cruel blood-sucker {sanguisuga crudelissima), believing that it’was used to increase the flow of blood. This view is, however, altogether without foundation, and from the observations of Osburn and others it is evident that the peculiarly shaped tongue is used by the animal, as in the case of the Macroglossi among the frugivorous Pteropodidae, to lick out the pulpy contents of fruits having hard rinds. The food of the species of this group appears to consist of both fruit and insects, and the long tongue may also be used for extracting the latter from the deep corollae of certain flowers.

Group III. Stcnodermata.— Muzzle very short and generally broad in front, the distance between the eyes nearly always exceeding (rarely equal to) the distance from the eye to the extremity of the muzzle; nose-leaf short, horse-shoe-shaped in front, lanceolate behind (except in Brachyphylla and Centurio)·, in ter femoral membrane always concave behind; tail none; inner margin of the lips fringed with conical papillae; i ∣ or ∣, pm f, m ⅜ or f or ∣; premolars and molars very broad (except in Sturnira), the latter with concave or flat crowns margined externally by raised cutting edges.

Although the Stenodermata are generally easily distinguished from the Vampyτi by the peculiar shortness and breadth of the muzzle, and by the form of the molar teeth, certain species of the latter group closely resemble those of the former in external appearance, agreeing almost absolutely in the form of the nose-lea f, of the ears and tragus, and of the warts on the chin. These resemblances show that, while the form of the teeth and jaws has become modified to suit the food of the animals, the external characters, being but slightly affected by this cause, have remained much the same, and now indicate their common origin. The food of these Bats appears to be wholly or in great part tree fruit. The twenty species nave been divided into nine genera, distinguished by the form of the skull and teeth. Artibeus, with five, includes among them the well-known frugivorous Bat, A. perspicillatus of Linnaeus, so common in collections. Stenoderma achradophilum,, found in Jamaica and Cuba, associated with the above, and scarcely distinguishable externally except by its very much smaller size, differs altogether in the absence of the horizontal plate of the palate bones. Sturnira lilium, while agreeing with the above in the form of the nose-leaf and ears, differs from all the species of the family in its longitudinally-grooved molars, which resemble those of the frugivorous Pteropodidae more closely than those of any other Bats; and the presence of tufts of long differently-coloured hairs over glands in the sides of the neck shows yet another character in common still more remarkable, which can scarcely be considered, like the teeth, the result of adaptive change. Centurio senex is the type of a genus distinguished from Stenoderma and other genera of this group by the absence of a distinct nose-leaf. This most remarkable form stands alone among the species of Chiroptera, and, indeed, in its peculiar and grotesque physiognomy is unrivalled among known mammals.

Group IV. Desmodontes.— Muzzle short aħd conical; nose-leaf distinct; interfemoral membrane very short; tail none; i ⅜, pm f, m ⅜ or ⅜; upper incisors very large, trenchant, occupying the whole space between the canines; premolars very narrow, with sharp-edged longitudinal crowns; molars rudimentary or none; stomach greatly elongated, intestiniform.

There are two genera, Ωesmodus, without calcaneum or true molars, and Dvphylla, with a short calcaneum and with a single rudimentary molar on each side,—restricted to Central and South America. Desmodus rufus, the commoner species, is a little larger than the Noctule Bat of Europe, and abundant in certain parts of South America, where it is very troublesome owing to its attacks upon domestic animals, sucking their blood and often leaving them much weakened from repeated bleedings. See Vampire. Fossil Chiroptera.

Fossil remains of Chiroptera extend as far back as the Upper Eocene of Europe and America, if, indeed, the beds in which they have been found are rightly considered as belonging to that age. Of these Vesperugo (Nyctitherium) parisiensis, described by Cuvier from the gypsum of Montmartre, is very like a small specimen of the widely distributed V. serotinus·, V. velox and priscus of the same subsection, and Nyctιlestes serotinus, have been characterized by Marsh from the Eocene of the United States, and Vespertilio morloti, Pictet, from that of Switzerland. From the Quercy lacustrine deposits comes Rhinolophus antiquus, Filhol, but these are very doubtfully of Eocene age. Palaeonycteris (allied to Rhinolophus), with P. robustus, Vesperugo, with V. noctuloides and murinoidcs, and Vespertilio, with V. aquensis, praecox, and insignis, have been found in Miocene beds of France and Germany. Pliocene bone caves have also yielded remains, in all cases closely allied to species now inhabiting the same countries. All these forms, however, exhibit as much specialization in their general structure as any existing species of the same families, indicating (if the age assigned to the deposits can be trusted) that the first appearance of Chiroptera must be referred to a very remote period.

Bibliography of Chiroptera.— G. E. Dobson. Catalogue of the Chiroptera in the Collection of the British Museum, 1878, including descriptions of all the species of Bats then known; subsequent papers by the same author in Bep. Brit. Assoc. Adv. Science, Proc. Zool. Soc., Ann. Mag. Nat. Hist., and Bullet. Soc. Zool. de France, by Peters in Monatsb. Akad. Wissensch. Berlin, and by Oldfield Thomas and J. Scully in Ann. Mag. Nat. Hist. ; H. A. Robin. Recherches Anatomiques sur les Mammifères de l' Ordre des Chiroptères, Paris, 1881.

Order RODENTIA.

Terrestrial, rarely arboreal or natatorial, diphyodont placental mammals of small size; with plantigrade or semiplantigrade, generally pentadactyle, unguiculate, rarely subungulate, feet; with clavicles (sometimes imperfect or rudimentary); with never more than two incisors in the mandible, and without canines.

The upper incisors resemble the lower in growing uninterruptedly from persistent pulps, and (except in Lagomorphd) agree with them in number; the premolars and molars are rooted or rootless, with tuberculated or laminated crowns, and arranged in an unbroken series; the orbits are not circumscribed by bone; the mandibular condyle is antero-posteriorly elongated; the intestine (except in Myoxidae) has a large caecum; the testes are inguinal or abdominal; the uterus is tw∙o-horned, the cornua opening separately into the vagina or uniting to form a corpus uteri; the placenta is discoidal · and deciduate; and the smooth cerebral hemispheres do not extend backwards so as to cover any part of the cerebellum.

The Rodents form a very compact order, τeadily distinguished by their large chisel-shaped incisors, and by the absence of canines. They include by far the greatest number of species (over 900), and have the widest distribution, of any of the orders of terrestrial mammals, being in fact cosmopolitan, although more abundant in some parts, as in South America, which may be considered their headquarters, than in others, as in Australasia and Madagascar, where representatives of a few genera of one family (Mvridae) only are found, thus contrasting remarkably with the Insectivore, which constitute at least half the mammalian fauna of Madagascar, but are without living representatives in South Anlerica.

If, as we have seen, the term entomophagous is applicable to most Insectivore, much more so, on the other hand, may the species of this great order be defined as phytophagous, and this uniformity in their food and in the mode of obtaining it, namely, by gnawing, has evidently led to such corresponding general uniformity in structure, which is observable throughout the species, that with difficulty we obtain characters sufficiently salient for dividing them into genera and families. Although, like the Insectivore, they present much diversity of habit,— some being arboreal, as the Squirrels, many species of which are provided with cutaneous parachutes on which they glide from tree to tree; some cursorial, as the Hares; some agile jumpers, as the Jerboas; some fossorial, as the great Mole-Rats; and some natatorial, as the Beavers and Water-Rats, —yet we do not find corresponding structural modifications comparable with those noticed in that order.

The Rodent skull is characterized by the great size of the premaxillary bones, which completely separate the nasals from the maxillaries, by the invariable presence of zygomatic arches, and by the wide unoccupied space existing between the alveoli of the incisors and the molar teeth, and (except in Lagomorpha) by the antero posteriorly elongated glenoid cavity. Post-orbital processes of the frontale exist only in the Squirrels, Marmots, and Hares; in all other genera they are rudimentary or altogether absent; the zygoma never sends upwards a corresponding process, and the orbit in all is freely continuous with the temporal fossa; the lachrymal foramen is always within the orbital margin; in many species the infra-orbital foramen is very large (in some as large as the orbit), and transmits part of the masseter muscle; the zygomatic arch is variously developed, and the position of the malar in it is used as a distinguishing character for grouping the families; the nasals are, with few exceptions, large, and extend far forwards; the parietals are moderate, and there is generally a distinct interparietal; the palate is narrow from before backwards,—this is especially pronounced in the Hares, where it is reduced to a mere bridge between the premolars,—in others, as in the great Rodent Moles (Bathyerginae), it is extremely narrow transversely, its width being less than that of one of the molar teeth; tympanic bullae osseae are always present and generally large; in some genera, as in the Gerbilles (Gerbillinae) and Jerboas (Dipodinae), there are supplemental mastoid bullae which form great hemispherical bony swellings at the back of the skull (see fig. 89, Per); in these genera, and in the true Hares, the meatus auditorius is tubular and directed upwards and backwards. The mandible is characterized by its abruptly narrowed and rounded symphysial part supporting the pair of large incisors, as well as by the small size of the coronoid process and great development of the ângular portion.

The dental formula varies from i - ∣ , c ⅞, pm ∣ , m f (total 28) in the Hares and Rabbits to i c ⅞, pm ⅞, m ⅜ (total 12) in the Australian .Water-Rats; but in the vast majority of the species it presents striking uniformity, and may be set down typically as i γ, c ⅞, pm t or ⅞, ni ⅞. In Lagomorplι<ι only are there more than a single pair of incisors, and in them the additional pair are small and placed quite behind the middle pair, and in this group alone does the enamel extend even partially to the back of the tooth; in all others it is restricted to its front surface, and so, by the faster wearing away of the softer structures behind, a chisel-shaped edge is always maintained. Both the upper and lower incisors are regularly curved, the upper slightly more so than the lower, and, their growth being continuous, should anything prevent the normal attrition by which their length is regulated, as by the loss of one of them, or by displacement owing to a broken jaw or other cause, the unopposed unused incisor may gradually curve upon itself until a complete circle or more has been formed, the tooth, perhaps, passing during its growth through some part of the animal’s head. The molar teeth may be rooted or rootless, tuberculated or laminated; and this diversity of structure may be noticed even in the same family. When there are more than three back teeth those which precede the last three have succeeded milk teeth, and must therefore be considered premolars. In some species, as in the Agoutis (Dasyproctidae), the milk teeth are long retained, while in the allied Cavies (Caviidae) they are shed before birth.

There are generally nineteen dorso-lumbar vertebrae (13 thoracic and 6 lumbar), and their forms vary in the different genera; in the cursorial and leaping species the lumbar transverse processes are generally very long, and in the Hares there are large compressed hypapophyses. The caudal vertebrae exhibit as much variety as in Insectivora, from their rudimentary condition in the Guinea-Pig to their great size in the Jumping Hares and prehensile - tailed Porcupines. The scapula is usually narrow, with a long acromion; the clavicles may be altogether absent or imperfect, as in the Porcupines, Cavies, and Hares, but in most species they are well developed; the humerus has no supra-condylar foramen, and the forearm bones are distinct; in most species the manus has five digits with phalanges normally developed, the pollex rarely rudimentary or absent. In contrast to the normal condition of the pelvis in Insectivora, we find here largely developed ischiatic and pubic bones, with a long usually osseous symphysis; the femur varies considerably in form, and there is generally a well-defined third trochanter; in the Sciurine and Hystricine Rodents the tibia and fibula are distinct, but in the Rats and other Murines, and in the Hares, these bones are united, often high up; the pes is much more variable than the manus, the digits varying in number from five, as in the Squirrels and Rats, to four, as in the Hares, or even three, as in the Capybara, Viscacha, and Agouti; in the Dipodidse the metatarsals are greatly elongated, and in some of the species, as in the Jerboas, they are ankylosed together.

The mouth is divided into two cavities communicating by a constricted orifice, an anterior containing the large incisors and a posterior in which the molars are placed, the hairy integument of the face being continued inwards behind the incisors. This evidently prevents substances not intended for food getting into the mouth, as when the animal is engaged in gnawing through an obstacle.. In the Hares and Pacas the inside of the cheeks is hairy, and in some species, as in the Pouched Rats and Hamsters, there are large internal cheek pouches lined with the hairy integument, which open near the angles of the mouth and extend backwards behind the ears; in the New-World Pouched Rats (Geomyidae) the pouches open externally on the cheeks.

The tongue presents little of that variability in length observable in the preceding orders; it is characteristically short and compressed, with an obtuse apex never protruded beyond the incisors; in most species there are, as in Insectivora, three papillae circumvallatae at the base; and the apical portion is generally covered with small filiform papillae, some of which in the Porcupines (Hystrix) become greatly enlarged, forming toothed spines. The stomach varies in form from the simple oval sac of the Squirrel to the complex ruminant-like organ of the Lemming. In the Water-Vole (Arvicola amphibius) and in the Agouti (Dasyprocta agouti) it is strongly constricted between the oesophagus and pylorus; in the common Dormouse the oesophagus immediately before entering the stomach is much dilated, forming a large egg-shaped sac with thickened glandular walls, and in some other species, as in Lophionιys imhausi and in the Beaver, glandular masses are attached to and open into the cardiac or pyloric pouches. All Rodents, with the exception only of the species of Dormice (Myoxidae), have a caecum, often of great length and sacculated, as in the Hares, Water-Voles, and Porcupines, and the long colon is in some, as in the Hamster and Water-Vole, spirally twisted upon itself near its commencement. The liver is typically divided in all, but the lobes are variously subdivided in the different species (in Capromys they are divided into minute lobules); and the gall-bladder, though present in most, is absent in a few. In most species, as in many Insectivora, the penis (which is generally provided with a bone) may be more or less completely retracted within the fold of integument surrounding the anus, and lie curved backwards upon itself under cover of the integument, or it may be carried forward some distance in front of the anal orifice, from which in the breeding season, as in the Voles and Marmots, the prominent testicular mass separates it. The testes in the rut form projections in the groins, but (except in Lagom,orpha) do not completely leave the cavity of the abdomen. Prostatic glands and, except in Lagomorpha, vesiculae seminales are present in all. The uterus may be double, each division opening by a separate os uteri into a common vagina, as in Leporidae, Sciuridae, and Hydrochoerus, or two-horned, as in most species. The mammary teats vary in number from the single.abdominal pair of the Guinea-Pig to the six thoracico-abdominal pairs in the Rats. In the Octodontidae the teats are placed high up on the sides of the body.

The peculiar odour evolved by many Rodents is due, as in the Insectivora, to the secretions of special glands, which may open into the prepuce, as in Mus, Arvicola, Cricetus, &c., or into the rectum, as in Arctomys and Aulacodus, or into the passage common to both, as in the Beaver, or into pouches opening near the anus, as in the Hare, Agouti, and Jerboa.

The integument is generally thin, and the panniculus carnosus rarely much developed. The fur varies exceedingly in character,—in some very fine and soft, as in the Chinchillas and Hares, in others more or less replaced by spines on 'the upper surface, as in the Spiny Rats and Porcupines; in several genera, as in Xerus, Acomys, Platacanthomys, Echiothrix, Loncheres, and Echinomys, the spines are flattened. In the muscular structures the chief peculiarities are noticeable in the comparatively small size of the temporal muscles, generally so largely developed in Insectivora, and in the great double masseters, which are the principal agents in gnawing; the digastrics also are remarkable for their well-defined central tendon, and in many speci⅞s their anterior bellies are united between the mandibular rami; the cleidomastoid generally arises from the basi-occipital, and the pectoralis major is connected with the latissimus dorsi; in the Porcupines and Hares the tendons of the flexor digitorum longus and flexor hallucis longus are connected in the foot, while in the Rats and Squirrels they are separate, and the flexor digitorum longus is generally inserted into the halluceal metatarsal. (See Dobson, Journ. Anat. Phys., vol. xvii.)

Suborder I. RODENTIA SIMPLICJDENTATA.

Rodents with two incisors only in the upper jaw, having their enamel confined to their front surfaces. The incisive foramina are moderate and distinct; the fibula does not articulate with the os calcis; and the testes are abdominal, and descend periodically only into the inguinal canal.

Section I. Sciuromorpha.

Zygomatic arch slender, chiefly formed by the malar, which is not supported by a long maxillary process extending backwards beneath it; post-orbital processes present or absent; infra-orbital opening small (except in Ano∞αZwws); mandible with the angular part arising from the inferior surface of the bony socket of the lower incisor; clavicles well-developed; fibula distinct.

Family 1. Anomaluridae.

Arboreal Rodents, having their limbs connected by a cutaneous expansion supported by a cartilaginous process arising from the olecranon; with a long hairy tail having large scales on its inferior surface near its root; with sixteen pairs of ribs, and without postorbital processes of the frontale; pm ⅛; molars not tuberculate, with transverse enamel folds. Ethiopian.

Anomalurus, with (?) five species from West Africa, alone represents the family. The peculiar caudal scales, which evidently assist the animal in climbing, and the position of the cartilaginous support of the parachute, are well shown in the above woodcut (fig. 93).

Family 2. Sciueidae.

Arboreal or terrestrial Rodents, with cylindrical hairy tails, without scales, and with twelve or thirteen pairs of ribs. Skull with distinct post-orbital processes; infra-orbital opening small; palate broad; pm f; first upper premolar very small or deciduous; molars rooted, tubercular.

Subfamily 1. Sciurinae.—Incisors compressed, form slender, tail long and hairy (True Squirrels). Cosmopolitan (excluding Australian region).

There are four genera. Pteromys,— limbs united by a cutaneous expansion forming a parachute, the supporting cartilage of which springs from the carpus,—includes the Flying Squirrels of both hemispheres. Sciurus, with more than eighty species, comprises the true Tree Squirrels. To’ this group also belong the Short-eared Squirrels of the genera Xerus and Tamias ; the first-named, distinguished from Sciurus by possessing only two pairs of mammary teats, by the comparatively short tail, and by the fur being mixed with flattened spines, includes a few African species which live in burrows; Tamias, separated by the presence of large internal cheek-pouches, includes the well-known Ground Squirrels of North America, of which one species (2 ’. asiat·icus) extends into North Europe and Asia. See Squirrel.

Subfamily 2. Arctomyinae.—Incisors not compressed; form stout; tail short (Marmots). Palaearctic and Nearctic.

Spermophilus, distinguished by its large cheek-pouches and by the absence or rudimentary condition of the pollex claw, resembles Tamias in the slender form of the body, and connects the Marmots with the true Squirrels. The distribution and habits of the species are similar to those of Tamias. Cynomys, with shallow cheekpouches, long pollex claw and stout form, includes the well-known Prairie Dogs peculiar to North America, which live together in large communities, inhabiting burrows which they excavate at short distances apart; they feed on the buffalo-grass which covers the plains. The small burrowing owl (Athene cuniculario) and the rattlesnake are often found inhabiting their burrows, the former probably availing itself of the convenience of a ready-made habitation, the latter coming there to feed on the young Marmots. Arctomys, distinguished by its rudimentary pollex, includes the true Marmots. See Marmot. Family 3. Haplodontidae.

Terrestrial Rodents, distinguished from Sciuridae by the absence of post-orbital processes, the depressed form of the skull, and the rootless molars. Premolars f, the first upper one small.

Haplodon, with H. rufus, from North America west of the Rocky Mountains, alone represents the family. The habits of the single species are similar to those of the Prairie Dog.

Family 4. Castoridae.

Natatorial Rodents, with massive skulls, without post-orbital processes, with mandibular angle rounded, and with semi-rooted or rootless molars with re-entering enamel folds; pm f.

Castor, with one species only, C. fiber, the Beaver of the northern parts of Asia, Europe, and America. The upper molars are subequal, each with one internal and two external enamel folds; the stomach has a large glandular mass situated to the right of the oesophageal orifice; the anal and urethro-genital orifices open within a common cloaca; the tail is broad, horizontally flattened, and naked; and the hind feet are webbed. See Beaver.

Section II. Myomoepha.

Zygomatic arch slender, the malar rarely extending far forwards, and usually supported below by the long zygomatic process of the maxillary; no post-orbital processes; infra-orbital opening variable; mandible with the angular part arising from the inferior surface of the bony socket of the lower incisor (except in Bathyerginae)·, clavicles well-developed (except in Lophiomys) ; tibia and fibula united.

Family 1. Myoxidae.

Arboreal Rodents, with long hairy tails, large eyes and ears, and short fore limbs. The intestine is without a caecum; the skull has contracted frontals; the infra-orbital foramen is moderate, high, and narrow; and the mandible has a long and slender coronoid process. Pm ⅛∙; molars rooted, with transverse enamel plates. Palaearctic and Ethiopian.

There are four genera :— Myoxus, with Μ. glis of Europe, with bushy, distichous tail, simple stomach, and large molars with well-marked enamel folds; Muscardinus, with Μ. avellanarius, the common Dormouse, distinguished by the cylindrical bushy tail and thickened glandular walls of the cardiac extremity of the oesophagus; Eliomys, with about six species, with tufted and distichous tail* simple stomach and smaller molar teeth with concave crowns and faintly marked enamel folds; and Graphiurus, with two species, with short cylindrical tail ending in a pencil of hairs, and very small molars almost without trace of enamel folds. The Dormice form a very natural family, distinguished from all other Rodents, by the absence of a caecum. In their habits and form they evidently closely approach the Squirrels.

Family 2. Lophiomyidae.

Arboreal Rodents, with rudimentary clavicles and rooted tuberculate molars. Premolars none. Skull murine in form, but the temporal fossae are completely arched over by thin plates arising-from the temporal ridge and malar bone. Intestine with a small caecum.

Lophiomys, with I.. imhausi (fig. 95), alone represents the family. This very extraordinary species from north-east Africa differs from all other Rodents in the peculiar granulated plates which cover the temporal fossae, and from all the species of the section in the rudimentary condition of the clavicles as well as in the possession of an opposable hallux. The hair is very peculiar in structure, and forms a crest along the back and tail. For full description see A. Milne-Edwards, I.’Institut, xxxv. p. 46.

Family 3. Mueidae.

Rodents of various habit, but generally terrestrial; with contracted frontals, with the lower root of the maxillary zygomatic process more or less flattened into a perpendicular plate; with a short and slender malar, generally reduced to a splint between the maxillary and squamosal processes; with (in typical forms) a high, perpendicular infra-orbital foramen, wide above and narrow below; with compressed lower incisors and rooted or rootless molars, tuberculate or with angular enamel folds. Premolars none (except in Sminthinae) ; pollex rudimentary; tail generally sub-naked and scaly.

This large family includes more than one-third of all the species of Rodents, and is represented by thirty-five generaOf cosmopolitan distribution. These fall into two sections corresponding to the rooted or rootless condition of the molars.

I. Molars rooted.

Subfamily 1. Sminthinae.— Pm ⅛, m ⅜; infra-orbital opening subtriangular, widest below; incisive foramina long.

Sminthus, with one species, S. vagus, a Rat-like Rodent inhabiting northern Asia and Europe.

Subfamily 2. Hydromyinae. M ⅜, divided into transverse lobes; infra-orbital opening crescentic, scarcely narrowed above; incisive foramina very small.

Hydromys, with two species from Australia, Tasmania, and New Guinea, includes the Water-Rats of the Australian region, with partially webbed toes. They are distinguished from all other Rodents by the small number of their molars.

Subfamily 3. Platacanthomyinae.— M ∣, with transverse laminae; fur mixed with flattened spines; tail densely hairy.

Platacanthomys, with P. lasiurus, a small Dormouse-like species from western India, inhabiting the rocky mountains of Travancore.

Subfamily 4. Gerbillinae.—Incisors narrow, molars with transverse laminae: auditory bullae osseae usually large; hind limbs elongated; tail generally long and hairy. Palaearctic, Indian, and Ethiopian.

Gerbillus, with nearly fifty species, has a range coextensive with that of the subfamily. Pachyuromys is distinguished by the enormous size of the auditory bullae, as well as by the short fleshy club-shaped tail. Mystromys, Otoτnys, and Dasymys differ in the form of the molars, and are represented by a few species, all from South Africa.

Subfamily 5. Phlaeomyinae.—Incisors broad, molars with transverse laminae; claws large. Indian.

Phlaeomys, with P. cumingii from the Philippines, and Ncsokia, with eight species widely distributed throughout the Indian Region. The latter (distinguished from the former genus by the short, subnaked, scaly tail) includes the Great Bandicoot Rat of India (AT. bandicota).

Subfamily 6. Dendromyinae. —Incisors convex in front, molars tuberculate; ears hairy; claws long. Ethiopian.

Three genera, Dendromys, Steatomys, and Lophurbmys, include several species of small Mouse-like Rodents with the habits of Dormice generally, though some burrow in corn-fields.

Subfamily 7. Cricetinae. —Molars tuberculate. Large internal cheek-pouches. Palaearctic and Ethiopian.

Of the three genera, Cricetus, Saccostomus, and Cricctomys, the last is distinguished from the others by the grooved Upper incisors, while Saccostomus is separated from Cricetus by the tubercles of the molar teeth being arranged in threes. The cheek pouches in Cricetus are very large, and their walls are connected with muscles arising from the lumbar vertebrae. The best-known species is C. frumentarius. See Hamster.

Subfamily 8. Murinεe. —Molars tuberculate, at least in youth. Cheek-pouches absent. Tail scaly, more or less naked. Cosmopolitan.

This includes the typical murine forms, divided into fifteen genera with over three hundred species, of which nearly half, however, are contained in the genus Mus. Μ. decumanus, the common Grey Rat, and Μ. musculus (see Mouse) are familiar examples which have been introduced in ships into almost every part of the habitable world. In Acomys the skull and teeth are as in Mus, but the fur is mixed with sharp flattened spines. A. dimidiatus presents the appearance of a little Hedgehog when its spines are erected; it inhabits the stony deserts of Arabia Petraea and Palestine, and feéds on bulbs. Echiothrix, Uromys, and Hapalotis, the latter with about a dozen species, are limited to the Australian region. Brachytarsomys, Nesomys, Eallomys, and Hypogeomys, each with one or two species, are peculiar to Madagascar, where they alone represent the order. Drymomys, Holocheilus, Ochetodon, and Hesperomys are New-World genera, the last-named including many species representing the Old-World Mice, but distinguished by the indenting enamel folds of the molars. Of the remaining genera, Reithrodon, with grooved incisors, includes two very remarkable Rabbit-like species, one inhabiting Patagonia, the other Tierra del Fuego.

II. Molars Semi-Rooted or Rootless.

Subfamily 9. Arvicolinae.—Molars composed of triangular prisms placed alternately; limbs moderate; tail moderate or short, hairy. Palaearctic and Nearctic.

Arvicola, with over thirty species, includes the Voles, of which the Field-Vole (A. agrestis) and the Water-Vole {A. ampħibius) are well-known examples (see Vole). Myodes, distinguished by the hairy foot-sole, includes two species, of which Μ. lemmus, of the Scandinavian Peninsula, is remarkable for its extraordinary migrations (see Lemming). Fiber is represented by a single large species, F. zibethicus (see fig. 94), the Musk-Rat, or Musquash, a Beaver-like Water-Rat with webbed toes, but a laterally flattened tail, inhabiting the banks of rivers and lakes in North America, and constructing dome-roofed dwellings like those of the Beaver; it is much hunted for its fur.

Subfamily 10. Siphneinae.—Molars as in Arvicolinae ; form cylindrical; ear-conch rudimentary; limbs and tail very short. Palaearctic.

Ellobius, with short claws, connects the species of this subfamily of fossorial Mole-like Rodents with the Arvicolinae. Siphneus, on the other hand, leads to the next family, which includes the true Mole-Rats; the species, which chiefly inhabit northern Asia, closely resemble the Golden Moles {Chrysochloris) in general form and in the great development of the claws of the fore feet (compare fig. 96 with fig. 64, p. 405).

Family 4. Spalacidae.

Rodent Moles, with very small or rudimentary eyes and ear-conchs, large claws, and short or rudimentary tail. Form cylindrical. Incisors large; molars rooted, with re-entering enamel folds; palate narrow.

Subfamily 1. Spalacinae.—Angular part of the mandible arising from the lower edge of the socket of the lower incisor. Palaearctic, Indian, and Ethiopian.

Spalax, with S', typhlus of south-east Europe, agrees with the insectivorous Golden Moles in the complete external absence of the eye, which is covered by the hairy skin, showing similar adaptive modification in widely removed species. In Rhizomys, including several species from China, Tibet, Malay Peninsula, and eastern Africa, the eye is very small.

Subfamily 2. Bathyerginse.—Angular part of the mandible arising from the side of the socket of the lower incisor. Ethiopian.

Bathyergus, with B. maritimus, the Great Rodent-Mole, inhabiting the sand-dunes along the coast in the vicinity of the Cape of Good Hope, is distinguished chiefly by its grooved incisors from the other species included in the genera Georychus and Heliophobius, the former with several, the latter with one species, and differing from both in the presence of two or three premolars.

Family 5. Geomyidae.

Terrestrial or fossorial Rodents, with large cheek-pouches opening on the cheeks outside the mouth. The squamosal bones are much expanded, and the malars extend forwards to the lachrymals. Pm ⅛; molars rooted or rootless. Nearctic and Neotropical.

Subfamily 1. Geomyinae.—Incisors broad; mastoid not appearing on the top of the skull; eyes small; ear-conch rudimentary; limbs short, subequal. Fossorial.

Geomys bursarius, the common Pouched Rat of North America, with deeply-grooved incisors, inhabits the plains of the Mississippi, living in burrows like the Mole. Four other species from the Southern States, Mexico, and Central America are recognized.. Thomomys talpoides, with plain incisors, extends all over Canada and North America west of the Rocky Mountains.

Subfamily 2. Heteromyin.se.—Incisors narrow; mastoid appearing largely on the top of the skull; eyes and ears moderate or large; hind limbs and tail elongated. Terrestrial.

Dipodomys has the molars rootless; D. phillipsi is the Kangaroo-Rat of the desert regions east of the Rocky Mountains. Perognathus and Heteromys have rooted molars; the latter genus is distinguished by the presence of flattened spines among the fur, with species extending into South America.

Family 6. Dipodidae.

Terrestrial leaping Rodents, of slender form, with elongated hind limbs. The incisors are compressed, the molars have transverse enamel folds, the infra-orbital opening is rounded and very large, the malar ascends in front to the lachrymal in a flattened perpendicular plate (see fig. 89, p. 415), and the mastoid part of the auditory bulla is usually greatly developed.

Subfamily 1. Zapodinae.—Molars rooted; cervical vertebrae free; metatarsals separate; hind feet with five digits. Nearctic.

Zapus ħudsonius, the American Jumping-Mouse, extends over almost the whole North-American continent from Labrador to Mexico.

Subfamily 2. Dipodinoe. —Molars rooted; cervical vertebrae more or less ankylosed; metatarsals united; hind feet with three functional digits only. Palaearctic and Ethiopian.

This includes the true Jerboas. It contains three genera: Dipus with three toes, and Alactaga and Platycercomys with five, the last-named distinguished by the total absence of premolars, comprising many species extending from Siberia to Nubia.

Subfamily 3. Fedetinεe.-Molars rootless; cervical vertebrae free; metatarsals separate; hind feet with four digits. Ethiopian.

Pedetes caffer, the Cape Jumping Hare, by far the largest species of the family, extends from Mozambique and Angola to the Cape of Good Hope. See Jerboa.

Section III. H ystricomorpha.

Zygomatic arch stout; malar not supported below by a continuation of the maxillary zygomatic process; infra-orbital opening large; mandible with the angular part arising from the outer side of the bony socket of the lower incisor; clavicles perfect or imperfect; fibula distinct.

Family 1. Octodontidae.

Terrestrial, rarely fossorial or natatorial Rodents, with perfect clavicles and long incisive foramina extending into the maxillaries. Malar with an inferior angle; molars with external and internal enamel folds; mammary teats placed high on the sides of the body.

Subfamily 1. Ctenodactylinae.—Molars semi-rooted; malar as in Dipodidae ; the two inner toes of the hind feet with a horny comb and rigid bristles. Ethiopian.

Ctenodactylus gundi and Pectinator spekei, both from North Africa, alone represent the subfamily; the peculiar comb-like inner toes are used in dressing the soft fur.

Subfamily 2. Octodontinae.—Molars semi-rooted or rootless, with simple enamel folds; fur soft. Ethiopian and Neotropical.

There are six genera, including several species of Rat-like Rodents. Octodon cumingii, common in Chili and Peru, about the size of a Rat, lives like Rabbits in large communities. Petromys typicus is the only African representative.

Subfamily 3. Echiomyinae. Molars semi-rooted or rooted, with deep, curved enamel folds; fur more or less harsh, often mixed with spines. Neotropical and Ethiopian.

Aulacodus, with A. swinderianus, the Ground-Rat of western Africa; the remaining nine genera are all Neotropical. Of these Myopotamus includes Μ. coypu, about 2 feet in length, the largest species of the family, common in South America, living in burrows near water, and feeding on aquatic plants. Capromys pilorides, nearly as large, is arboreal in habits, and inhabits Cuba and Hayti, where it is the largest indigenous mammal; the species of this genus are remarkable for the manner in which the liver is divided into minute lobules. Plagiodontia aedium is peculiar to Hayti and Jamaica, and in the latter island (besides Bats and Mice, the latter probably introduced) appears to be the only indigenous mammal. In Loncheres and Echinomys most of the species have the fur mixed with flattened lanceolate spines.

Family 2. Hystricidae.

Terrestrial or arboreal Rodents, of stout form, with subequal limbs and more or less spiny integument. Malar without an inferior angle; the facial part of the skull short and broad; molars with external and intern M enamel folds.

Subfami y 1. Spingurinεe.—Molars rooted; clavicles perfect; •soles of feet tuberculated; teats four; tail generally prehensile. Arboreal. Nearctio and Neotropical.

There arc three genera, including several species. Of these Erethizon dorsatus, the Urson, is distributed? all over the forest regions of North America; Sy nether es ( = Cercolabes) prehensilis, the well-known prehensile-tailed Porcupine of South America (fig. 98), has the whole upper surface of the body protected by long white-tipped spines; Chsetomys subspinosus is clothed with strong wavy bristles; in the last two genera the feet have four digits only.

Subfamily 2. Hystricinøe. —Molars semi-rooted; clavicles imperfect; soles of feet smooth; teats six; tail not prehensile. Terrestrial. Palaearctic, Indian, and Ethiopian.

Hystrix cristata, the Common Porcupine of southern Europe and northern Africa, is typical of this genus, which includes several other species from the Indian region. The spines are cylindrical, the tail short and covered with spines and slender stalked open quills. In Atherura fasciculata of the Malay Peninsula the spines are flattened, and the tail is long and scaly, with a tuft of compressed bristles. A closely allied species, A. africana, inhabits western Africa. See Porcupine. Family 3. Chinchillidae.

Terrestrial Rodents, with elongated hind limbs, bushy tails, very soft fur, and perfect clavicles. The malar is without an inferior angle, and extends forwards to the lacrymal; the palate is contracted in front and deeply emarginate behind; the incisors are short, and the molars divided by continuous folds into transverse laminae. Neotropical.

This small family includes only three species, divided into as many genera. Chinchilla lanigera and Lagidium peruanum are restricted to the alpine zones of the Andes from the northern boundary of Peru to the southern parts of Chili, and Lagostomus trichodactylus, the Viscacha, to the pampas from the Uruguay river to the Rio Negro. In Chinchilla the fore feet have five and the hind four digits, the tail is long and bushy, and the auditory bull® are enormous, appearing on the top of the skull; Lagidium has four digits in both fore and hind feet, and Lagostomus three only in the hind feet, while the auditory bullae are much smaller. See Chinchilla. Family 4. Dasyproctidae.

Terrestrial Rodents, with subequal limbs, hoof-like claws, short or obsolete tail, and rudimentary clavicles. Mandibular masseteric ridge obsolete; palate broad; incisors long; molars semi-rooted, with external and internal enamel folds. Neotropical.

With two genera:— Dasyprocta,iruAa< ∖ vag several species of slender-limbed, subungulate Rodents with three hind toes, inhabiting Central and South America, one (7λ cristata) extending into the West-Indian Islands; and Coelogenys, with five hind toes, remarkable for the extraordinary development of its zygomatic arches, which are enormously expanded vertically, forming great convex bony capsules on the sides of the face, enclosing on each side a large cavity lined with mucous membrane internally, and communicating by a small opening with the mouth; C. paca is about 2 feet long, and, like the species of Dasyprocta, lives generally in the forests or along the banks of rivers.

Family 5. Dinomyidae.

Terrestrial Rodents, distinguished from Dasyproctidae by the cleft upper lip and rather long and bushy tail, and by the presence of four digits in the fore and hind feet. The manubrium is broad; the optic foramina are confluent, the incisors broad and the molars rootless, with-folds dividing them into transverse lobes.

This family includes but a single species, Dinomys branickii, known only from a single specimen obtained in Peru, which resembles Coelogenys paca in the general form of its body and in size. It is regarded by its describer, Professor Peters, as a connecting link between the families Ododontidae, Chinchillidae, Dasy- prodidae, and Caviidae. Family 6. Caviidae.

Terrestrial or natatorial Rodents, with short incisors, strong mandibular masseteric ridges, long and curved paroccipitals, and palate contracted in front. Fore feet with four digits, hind feet with three; clavicles imperfect; molars divided by enamel folds into transverse lobes; milk teeth shed before birth. Other characters as in Dasyprodidae. Neotropical.

Cavia, limbs and ears short, subequal, tail none, includes several species widely distributed throughout South America, extending even to the Straits of Magellan, from one of which (C ’. aperça, probably) the common Guinea-Pig is derived. Dolichotis has the limbs and ears long, tail very short, with D. patagonica, a large species, nearly 3 feet long, inhabiting the gravelly plains of Patagonia. The palate is so much contracted in front that the premolars of opposite sides touch by their antero-internal edges. Hydrochoerus, with all the feet fully webbed, also includes a single species, which is the largest of living Rodents. The skull (fig. 97) is distinguished, not only by its great size, but also by the enormous development of the paroccipital processes. See Cavy and Capybara. Suborder II. FODENT I A DUPLICIDENTATA.

Rodents with four incisors in the upper jaw (two of them very small, and placed directly behind the large middle pair), the enamel of which extends round to their posterior surfaces. At birth there are six of these incisors, but the outer one on each side is soon lost. The incisive foramina are large and usually confluent; the bony palate is very narrow from before backwards; there is no true alisphenoid canal; the fibula is ankylosed to the tibia, and articulates with the os calcis; and the testes are permanently external.

Section IV. Lagomorpha.

Characters those of the suborder.

Family 1. Lagomyidae.

Terrestrial Rodents, with complete clavicles, subequal limbs, no external tail, and short ears. Skull depressed, frontale contracted and without post-orbital processes; pm ⅜ or ⅜; molars rootless, with transverse enamel folds. Palaearctic and Nearctic.

Lagomys, with about a dozen species of small Guinea-Pig-like animals, inhabiting chiefly the mountainous parts of northern Asia (from 11,000 to 14,000 feet), one species only being known from south-east Europe and one from the Rocky Mountains.

Family 2. Leporidae.

Terrestrial Rodents, with imperfect clavicles, elongated hind limbs, short recurved tail, and. long ears. Skull compressed, frontale with large wing-shaped post-orbital processes (fig. 99); pm ⅞; molars as in Lagomyidae. Cosmopolitan (except Australasia).

Lepus includes about twenty species, which all resemble one another in general external characters. In all the fore limbs have five and the hind only four digits, and the soles of the feet are densely clothed with hairs similar to those covering the legs; the inner surface of the cheeks also is hairy. Although the family has such a wide distribution, the greater number of the species are restricted to the Palaearctic and Nearctic regions, and a single species only (Z. brasiliensis') extends into South America. See Habe and Rabbit. Fossil Rodentia.

Fossil representatives of all the above-defined families, with the exception only of the small groups included under Anomaluridae, Haplodontidae, Lophiomyidae, Spalacidae, and Dinomyidae, have been described from various deposits. Of these the earliest have been found in the Upper Eocene of Europe and America, and belong to the family Sduridae, of which the genera Colonomys, Taxymys, Tillomys, Paramys, Heliscomys, and Mysyops have been characterized from Eocene of North America, and Plesiarctomys from that of both America and France, while examples of even the recent genus Sciurus have been found in beds of the same age in the latter country. Other recent families have representatives in later deposits, as Castoridae with Steneofiber and Palaeomys from the Miocene of Europe and North America, Trogonotherium from that of India, Chalicomys from that of Germany, and Eucastor from North America, Myoxidae with Myoxus and Muridae with Elomys, Dedicus, 0reomys, and Cricetodon from the European Miocene, Hystriddae with Erdhizon extending back to the Miocene of India, Geomyidae with Entoptychus and Pleurolicus and Dasyprodidae with Paciculus from the Miocene of North America, Lagomyidae with Titanomys and Myolagus from the European Miocene, and Leporidae with Palaeolagus from corresponding North American beds. Later Tertiary strata havt yielded Rodent remains more abundantly; many of them referable to recent genera, or even closely allied to or undistinguishable from existing species, have been described from Brazilian bone-caves.

Besides those referable to existing families, several fossil remains have been discovered which cannot be so classed. These have been included in three families :— Ischromyidae with Pseudotomus from the Eocene, and Ischromys and Gymnoptychus from the Miocene of North America; TheriUomyidae with Theridomys extending from the Eocene to the Pliocene of France, and Archaeomys, Issidioromys, and Dipoides from the Miocene; and Castoroididae with Castoroides from post-Pliocene deposits of North America, and Amblyrhiza and Loxomylus from the bone-breccias of the island of Anguilla. The first-named family appears to be intermediate between the Sduridae and Castoridae ; the second is allied to Geomyidae and Dipodidae ; and the last, connected with Chinchillidae, includes Castoroides ohioensis, a species vastly exceeding in size the largest of existing Rodents. A fourth family, Mesotheriidae, including a single fossil form, Mesotherium cristatum, also of large size, from the Pliocene of South America, has been referred to this order, but it is evident that ah animal which, besides presenting many other structural differences, possesses four lower incisors completely surrounded by enamel, and in which the mandibular condyle is transversely extended and the maxillaries articulate freely with the nasals, cannot be considered as coming under the definition of a Rodent.

Thus, like the Insedivora and Chiroptera, fossil remains of Rodentia are found as far back as the Eocene period, and of these some are even referable to one or more recent genera, and differ but slightly from existing species, while all others are either capable of being classed in recent families or are more or less closely related to them. It follows therefore (if the age of the beds in which these remains were found has been correctly determined) that, as in the case of these orders also, the first appearance of true Rodents must be sought for much farther back in time, and the question of their descent must be deferred till the discovery of sufficient material admits of reliable generalizations.

Bibliography of Rodentia. — G. R. Waterhouse, “Observations on the Rodentia," Mag. Nat. Hist., iii. (1839); Id., Ann. Nat. Hist., viii. and x. (1839-42); Id., “On the Geographical Distribution of the Rodentia,” Proc. Zool. Soc., 1839, pp. 162-174; Id., Natural History of the Mammalia, vol. ii., “Rodentia,” (1848); Gervais, Diet. Univ. d'Hist. Nat., xi., p. 202 (1848); Brandt, “Untersuchungen über die craniologischen Entwickelungsstufen und Classificati n der Nager der Jetzwelt,” Mém. de l'Acad. Imper, de St Pétersbourg (1855); Lilljeborg, Systematisk Oefversight af de Gnagande Däggdjuren, Upsala, 1866: Alston, “On the Classification of the Order Glires,” Proc. Zool. Soc., 1876, pp. 61-98; Trouessart, “Catal. de Rongeurs, Vivants et Fossiles,” Bullet. Soc. d ’ Études Scient. d'Angers, 1880-1; various papers by Peters in Monatsb. Akad. Wissensch. Berlin, and by Alston, Anderson, Blandford, A. Milne-Edwards, Thomas, and others, in Proc. Zool. Soc., Jour. Asiat. Soc. Beng., Ann. Mag. Nat. Hist., <fcc.

[For the above sections on the Insedivora, Chiroptera, and Rodentia we are indebted to Dr G. E. Dobson.]

Order UNGULATA.

Under this term may be included provisionally a large and rather heterogeneous group of mammals, the existing members of which form the Pecora and Belluae of Linnaeus, the Ruminantia and Pachydermata of Cuvier. A few years ago it was found convenient to restrict the order to a well-marked and distinctly circumscribed group, comprising the two sections known as Perissodactyla and Aτtiodactyla, and to leave out such isolated forms as the Elephant and Hyrax; but the discovery of a vast πumb∈τ of extinct species, which could not be brought under the definition of either Perissodactyle or Artiodactyle Ungulates, and yet are evidently allied to both, and which to a certain extent bridge over the interval between these and the isolated groups just mentioned, makes it necessary either to introduce a number of new and ill-defined ordinal divisions, or to widen the scope of the original order so as to embrace them all.

They are all animals eminently adapted for a terrestrial life, and in the main for a vegetable diet. Though a few are more or less omnivorous, and may under some circumstances kill living creatures smaller and weaker than themselves for food, none are distinctly and habitually predaceous. Their teeth are markedly heterodont and diphyodont,—the milk set being well developed and not completely changed until the animal attains its full stature. The molars have broad crowns with tuberculated or ridged surfaces. They have no clavicles. Their toes are provided with blunt, broad nails, or in the majority of cases with hoofs, more or less enclosing the ungual phalanges. The scaphoid and lunar bones of the carpus are always distinct.

The whole group may be divided into the Ungulata Vera, containing the suborders Perissodactyla and Artiodactyla, and a less well-known assemblage of animals which may be called Subungulata or Ungulata Polydactyla. Cope has pointed out a character in the structure of the carpus by which the latter are differentiated from the former. In all the Subungulata the bones of the proximal and distal row retain the primitive or more typical relation to each other· (see fig. 100). The os magnum of the second row articulates mainly with the lunar of the first, or with the cuneiform, but not with the scaphoid, while in the group to which the vast majority of modern Ungulates belong the second or distal row has been shifted altogether towards the inner side of the limb (see figs. 107 and 109), so that the magnum is brought considerably in relation with the scaphoid, and is entirely removed from the cuneiform, as in the great majority of existing mammals.

SUBUNGULATA.

By far the greater number of the Subungulata are extinct, and of many of those whose former existence has been revealed, chiefly by the labours of the American palaeontologists, our knowledge is at present necessarily imperfect, though daily extending. It will only be possible here to give any details of some of the more interesting or best-known forms.

Suborder HYRAC01DEA.

This division is constituted to receive a single family of mammals, the affinities of which have long constituted a puzzle to zoologists. They were first placed among the Rodents, to which animals their small size and general appearance and habits give them much superficial resemblance. Cuvier’s investigations into their anatomical structure, and especially their dental characters, led him to place them among the Ungulates, near the genus Rhinoceros, a position still accepted by many zoologists. Further knowledge of their organization and mode of development has caused Milne-Edwards, Huxley, and others to disassociate them from this connexion, and, failing to find any agreement with any other known forms, to place them in a group entirely apart. Palaeontology has thrown no light upon the affinities of this anomalous and isolated group, as no extinct animals possessing their distinctive characters have as yet been discovered.

The dentition consists only of incisors and molars, the formula in all known species being i ∣ , c ⅞, p ∣ , m ⅜. The upper incisors have persistent pulps, and are curved longitudinally, forming a semicircle as in Rodents. They are, however, not flattened from before backwards as in that order, but prismatic, with an antero-external, an antero-internal, and a posterior surface, the first two only being covered with enamel; their apices are consequently not chisel-shaped, but sharp pointed. They are preceded by functional, rooted milk teeth. The lower incisors have long tapering roots, but not of persistent growth. They are straight, procumbent, with awl-shaped, trilobed crowns. Behind the incisors is a considerable diastema or interval. The molars and premolars are all contiguous, and formed almost exactly on the pattern of some of the Perissodactyle Ungulates. The hyoid arch is unlike that of any known mammal. The dorsal and lumbar vertebrae are very numerous, 28 to 30, of which 21 or 22 bear ribs. The tail is extremely short. There are no clavicles. In the fore foot, the three middle toes are subequally developed, the fifth is present, but smaller, and the hallux is rudimentary, although, in one species at least, all its normal bones are present. The ungual phalanges of the four outer digits are small, somewhat conical, and flattened in form. The carpus has a distinct os centrale. There is a slight ridge on the femur in the place of a third trochanter. The fibula is complete, thickest at its upper end, where it generally ankyloses with the tibia. The articulation between the tibia and astragalus is more complex than in other mammals, the end of the malleolus entering into it. The hind foot is very like that of Rhinoceros, having three well-developed toes. There is no trace of a hallux, and the fifth metatarsal is represented by a small nodule only. The ungual phalanx of the inner (or second) digit is deeply cleft, and has a peculiar long curved claw, the others having short broad nails. The stomach is formed upon much the same principle as that of the Horse or Rhinoceros, but is more elongated transversely and divided by a constriction into two cavities—a large left cul de sac, lined by a very dense white epithelium, and a right pylorio cavity, with a very thick, soft, vascular lining. The intestinal canal is long, and has an arrangement perfectly unique among mammals, indeed among vertebrated animals, for, in addition to the ordinary short, but capacious and sacculated caecum at the commencement of the colon, there is, lower down, an additional pair of large, conical, pointed caeca. The liver is much subdivided, and there is uo gall-bladder. The brain resembles that of the typical Ungulates far more than the Rodents. The testes are permanently abdominal. The ureters open into the fundus of the bladder as in some Rodents. The female has six teats, of which four are inguinal and two axillary, and the placenta is zonary, as in the Elephant and Carnivora.

There are two distinct forms of Hyrax, differing both in structure .and habits, and which may well be accorded generic rank.

1. Hyrax.— Molar teeth having the same pattern as those of Rhinoceros. Interval between upper incisors less than the width of the teeth. Lower incisors slightly notched at the cutting edge. Vertebrae: C 7, D 22, I. 8, S 6, C 6. Of this form the earliest known species, H. capensis, is the type. There are several other species, as _ZZ. syriacus and habessinicus, from eastern Africa and Syria. They inhabit mountainous and rocky regions, and live on the ground.

2. Dendrohyrax.— Molar teeth having the same pattern as Palaeo· therium (except that the third lower molaι ’ has but two lobes). Interval between upper incisors exceeding the width of the teeth. Lower incisors with very distinctly trilobed crowns. Vertebrae: •C 7, D 21, I. 7, S 5, C 10. The members of this section frequent the trunks and large branches of trees, sleeping in holes. There are several species, not distinctly defined, from western and south Africa, as D. arboretis and I). dorsalis. The members of both groups appear to have a power like that possessed by the Lizards called Geckos of clinging to vertical surfaces of rocks and trees by the .soles of their feet. See Hyrax.

The anatomy of Hyrax was first described by Pallas {Spicilegia Zoologica). Besides minor memoirs, two very detailed accounts of its structure have recently •appeared—one by Brandt, in Mem. Acad. Nat. Seien. St Pétersbourg, series vii. vol. xiv., No. 2, 1869; and another by George, in Annates des Sciences Naturelies, series vi. tom. i., 1874, in which references to all the previous literature will be found. The mechanism by which the sole of the foot is enabled to adhere to smooth surfaces is fully described by G. E. Dobson, Proc. Zoo ∣ . Soc., 1876, p. «26.

Suborder PROBOSCIDEA.

This name has been appropriated to a well-marked group of animals, presenting some very anomalous characters, allied in many respects to the Ungulata, but belonging neither to the Artiodactyle nor Perissodactyle type of that order. It has been thought that they possess some, though certainly not very close, affinities with the Rodentia, and also with the Sirenia. It is certain, however, that the two species of Elephant which are the sole living representatives of the group, stand quite alone among existing mammals, differing widely from all others in many points of their structure. In some respects, as the skull, proboscis, and dentition, they are highly specialized, but in others, as in the presence of two .anterior venae cavae, and in the structure of the limbs, they retain a low or generalized condition. A considerable series of extinct forms, extending hack through the Pliocene and Miocene epochs, show the same type under different modifications, and in still more generalized outlines; and certain recently discovered forms from the Eocene of North America, if their affinities are rightly interpreted, appear to link the true Proboscidea to some unknown primitive type of Perissodactyle Un- 'gulata.

The following are the principal characters common to existing, and, by inference, to the extinct, Proboscidea. The nose extended into a long, muscular, very flexible and prehensile proboscis, at tho end of which the nostrils are situated, and from which the namo given to the group is derived. The teeth consisting of ever-growing incisors of very great size, but never exceeding one pair in each jaw, and often present in one jaw only; no canines; large and transversely ridged molars. No clavicles. Limbs strong, the upper segment, especially in tho hind limb, tho longest. Radius and ulna distinct, the latter articulating extensively with the carpus. Fibula and tibia distinct. Astragalus very flat on both surfaces. Manus and pes short, broad, and massive, each with five toes, though the outer pair may be more or less rudimentary, all encased in a common integument, though with distinct, broad, short, hoofs. Third digit the largest. Two anterior venae cavae entering the right auricle. Stomach simple. A capacious caecum. Testes permanently abdominal. Uterus bicornuate. Placenta non-deciduate and zonary. Mammae two. pectoral.

With regard to the teeth, the incisors, whieh project largely out of the mouth, and are commonly called “tusks,” are of an elongated conical form, and generally curved. They are composed mainly of solid dentine, the fine elastic quality and large mass of which renders it invaluable as “ivory” for commerce and the arts. A peculiarity of the dentine of the Proboscidea is that it shows, in transverse fractures or sections, striae proceeding in the arc of a circle from the centre to the circumference in opposite directions, and forming by their decussations curvilinear lozenges, as in the “engine-turning” of the case of a watch. The enamel covering in existing species is confined to the extreme apex, and very soon wears off, but in some extinct species it forms persistent longitudinal bands of limited breadth. The tusks have small milk predecessors, shed at an early age.

The molar teeth present a remarkable series of modifications from the comparatively simple form in Dinothérium., with two or three strongly pronounced transverse ridges and a normal mode of succession, to the extremely complex structure and anomalous mode of replacement found in the true Elephants. The intermediate conditions occur in the various species of Mastodon. In this genus the enamel-covered transverse ridges of each tooth are generally more numerous than in Dinothérium, and often complicated by notches dividing their edge or by accessory columns attached to them, but in the unworn tooth they stand out freely on the surface of the crown, with deep valleys between (fig. 102, I). In the Elephants the ridges are still further increased in number, and consequently narrower from before backwards, and are greatly extended in vertical height, so that, in order to give solidity to what would otherwise be a laminated or pectinated tooth, it becomes necessary to envelop and unite the whole in a large mass of cementum, which completely fills up the valleys, and gives a general smooth appearance to the organ when unworn; but as the wear consequent upon the masticating process proceeds, the alternate layers of tissue of different hardness—cementum, dentine, and enamel—which are disclosed upon the surface form a fine and very efficient triturating instrument. The modification of the tooth of a Mastodon into that of an Elephant is therefore precisely the same in principle as that of the mplar of a Palaeotherium into that of a Horse (see vol. xiii. p. 174), or of the corresponding tooth of one of the primitive Artiodactyles into that of an Ox. The intermediate stages, moreover, even in the present state of our knowledge, are so numerous that it is not possible to draw a definite line between the two types of tooth structure (see fig. 102, II, III, IV).

As regards the mode of succession, that of modern Elephants is, as before mentioned, very peculiar. During the complete lifetime of the animal there are but six molar teeth on each side of each jaw, with occasionally a rudimentary one in front, completing the typical number of seven. The last three represent the true molars of ordinary mammals; those in front appear to be milk molars, which are never replaced by permanent successors, but the whole series gradually moves forwards in the jaw, and the teeth become worn away and their remnants cast out in front, while development of others proceeds behind. The individual teeth are so large, and the processes of growth and destruction by wear take place so slowly, that not more than one, or portions of two, teeth are ever in place and in use on each side of each jaw at one time, and the whole series of changes coincides with the usual duration of the animal’s life. On the other hand, the Dinothérium, the opposite extreme of the Proboscidean series, has the whole of the molar teeth in place and use at one time, and the milk molars are vertically displaced by premolars in the ordinary fashion. Among Mastodons transitional forms occur in the mode of succession as well as in structure, many species showing a vertical displacement of one or more of the milk molars, and the same has been observed in one extinct species of Elephant (Ä planifrons) as regards the posterior of these teeth.

All known Proboscideans are animals of large dimensions, and some are the most colossal of land mammals. The head is of great proportionate size; and, as the brain case increases but little in bulk during growth, while the exterior wall of the skull is required to be of great superficial extent to support the trunk and the huge and ponderous tusks, and to afford space for the attachment of muscles of sufficient size and strength to wield the skull thus heavily weighted, an extraordinary development of air-cells takes place in the cancellous tissue of nearly all the bones of the cranium. These cells are not only formed in the walls of the cranium proper, but are also largely developed in the nasal bones and upper part of the premaxillae and maxillae, the bones forming the palate and the basi-cranial axis, and even extend into the interior of the ossified mesethmoid and vomer. Where two originally distinct bones come into contact, the cells pass freely from one to the other, and almost all the sutures become obliterated in old animals. The intercellular lamellae in the gre⅛t mass which surrounds the brain cavity superiorly and laterally mostly radiate from the inner to the outer table, but in the other bones their direction is more irregular. Like the similar but less developed air-cells in the skulls of many other mammals, they all communicate with the nasal passages, and they are entirely secondary to the original growth of the bones, their development having scarcely commenced in the new-born animal, and they gradually enlarge as the growth of the creature proceeds towards maturity. The nasal bones are very short, and the anterior narial aperture situated high in the face. The zygomatic arch is slender and straight, the malar bones being small, and forming only the middle part of the arch, the anterior part of which (unlike that of all true Ungulates) is formed only by the maxilla. The maxillo-turbinals are but rudimentary, the elongated proboscis supplying their place functionally in warming and clearing from dust the inspired air.

The neck is very short. The limbs are long and stout, and remarkable for the great length of the upper segment (especially the femur) as compared with the distal segment, the manus and pes. It is owing to this and the vertical position of the femur that the knee-joint in the hind leg is placed much lower, and is more conspicuous externally than in most quadrupedal mammals, and, this having been erroneously compared with the hock-joint or ankle of Ungulates, the popular fallacy that the joints of the Elephant’s leg bend in a contrary direction to that of other mammals has arisen. There is no round ligament in the hip-joint, or third trochanter to the femur. The radius and ulna are distinct, though fixed in a crossed or prone position. The fibula also is quite distinct from the tibia. The feet are short and broad, the carpal and tarsal bones being very square, with flattened surfaces for articulation; the astragalus especially differs from that of true Ungulates in its flatness, in the absence of a distinct pulley-like articular surface at either extremity, and in having no articular facet for the cuboid. The fibula articulates with the calcaneum, as in Artiodactyles. Of the five toes present on each extremity (see fig. 100), the middle one is somewhat the largest, and the lateral ones smallest, and generally wanting (especially in the hind foot) the complete number of phalanges. The ungual phalanges are all small, irregular in form, and late in ossification. The whole are encased in a common integument, with a flat, subcircular, truncated sole, the only external indication of the toes being the broad oval nails or hoofs arranged in a semicircle around the front edge of the sole. The hind foot is smaller and narrower than the front. The liver is small and simple, and there is no gallbladder. In form the brain resembles that of the Rodents and other lower orders of mammals, the cerebellum being entirely behind and uncovered by the cerebrum, but the hemispheres of the latter are richly convoluted.

The Probosddea are exclusively vegetable feeders, living chiefly on leaves and young branches of forest trees and various kinds of herbage, which they gather and convey to their mouth by the very mobile proboscis, an organ which combines in a marvellous manner strength with dexterity of application, and is a necessary compensation for the shortness and inflexibility of the neck, as by it many of the functions of the lips of other animals are performed. By its means the Elephant is enabled to drink without bending the head or limbs; the end of the trunk being dipped into the stream or pool, a forcible inspiration fills the two capacious air-passages in its interior with water, which, on the tip of the trunk being turned upwards and inserted into the mouth, is ejected by a blowing action, and swallowed; or if the animal wishes to refresh and cool its skin, it can throw the water in a copious stream over any part of its surface. Elephants can also throw dust and sand over their bodies by the same means and for the same purpose, and wild animals have been frequently observed fanning themselves with leafy boughs held in the trunk. The species are at present limited in their geographical distribution to the Ethiopian and Oriental regions, but they formerly had a far more extensive range.

Elephas. — Dentition: i ⅜, c ⅜,,m ⅜ = 26. The incisors variable, but usually of very large size, especially in the male sex, directed somewhat outwards, and curved upwards, without enamel except on the apex before it is worn; preceded by small milk incisors. The molars succeed each other by horizontal replacement from before backwards, never more than one or part of two being in use on each side of each jaw at the same time; each composed of numerous flattened enamel-covered plates or ridges of dentine, projecting from a common many-rooted base, surrounded and united together by cementum. The number of plates increases from the anterior to the posterior molar in regular succession, varying in the different species, but the third and fourth (or the last milk molar and the first true molar), and these only, have the same number of ridges, which always exceeds five. Skull of adult very high and globular. Mandible ending in front in a prolonged deflected and spout-like symphysis. Vertebrae: C 7, D 19-21, I. 3-4, S 4, C 26-33.

The existing species of the genus differ so much that they must be placed in two distinct sections, considered by some zoologists as distinct genera.

1. Elephas proper. Elasmodon, F. Cuv.; Euelephas, Falc.—∙. Average number of plates of the six successive molar teeth expressed by the “ridge formula” 4, 8, 12, 12, 16, 24. The plates compressed from before backwards, the anterior and posterior surfaces (as seen in the worn grinding face of the tooth) being nearly parallel. Ears of moderate size. Upper margin of the end of the proboscis developed into a distinct finger-like process, much longer than the lower margin. Five nails on the fore feet, and four (occasionally five) on the hind feet.

The well-known Asiatic Elephant, E. indicus, inhabits in a wild state the forestlands of India, Burmah, the Malay Peninsula, Cochin China, Ceylon, and Sumatra. Those from the last-named islands, presenting some variations from those of the mainland, have been separated under the name of E. sumatranus, but the distinction has not been satisfactorily established. The appearance of the Asiatic Elephant is familiar to all. Though rarely breeding in captivity, it has been domesticated from the most remote antiquity, and is still extensively used in the East as a beast of burden. In the wild state it is gregarious, associating in herds of ten, twenty, or more individuals, and, though itmay under certain circumstances become dangerous, it is generally inoffensive and even timid, fond of shade and solitude and the neighbourhood of water. The height of the male at the shoulder when full grown is usually from 8 to 10 feet, occasionally as much as 11. The female is somewhat smaller. See Elephant.

2. Loxodon.— Molar teeth of coarse construction, with fewer and larger plates and thicker enamel. Ridge formula: 3, 6, 7, 7, 8, 10. The plates not flattened, but thicker in the middle than at the edges, so that their worn grinding surfaces are lozenge-shaped. Ears very large. The upper and lower margins of the end of the trunk forming two nearly equal prehensile lips. But three hoofs on the hind foot. The one species, E. africanus, now inhabits the wooded districts of the whole of Africa south of the Sahara, except where it has been driven away by human settlements. Fossil remains of Pleistocene age, undistinguishable specifically, have been found in Algeria, Spain, and Sicily. It was trained for war and show by the ancient Carthaginians and Romans, and recent experience of the species in captivity in England shows that it is as intelligent as its Asiatic relative, if not more so, while surpassing it in courage, activity, and obstinacy. Nevertheless, in modern times, no people in Africa have been sufficiently civilized or enterprising to care to train it for domestic purposes. It is hunted chiefly for the sake of the ivory of its immense tusks, of which it yields the principal source of supply to the European market, and the desire to obtain which is rapidly leading to the extermination of the species. In size the male African elephant often surpasses that of Asia, but the female is usually smaller. The circumference of the forefoot is half the height at the shoulder, a circumstance which enables the hunters to judge from the footprints the exact size of the animals of which they are in pursuit.

Extinct Species of Elephant.— Abundant remains of Elephants are found embedded in alluvial gravels, or secreted in the recesses of caves, into which they have been washed by streams and floods, or dragged as food by Hyaenas and other carnivorous inhabitants of these subterranean dens. Such remains belonging to the Pleistocene and Pliocene periods have been found in many parts of Europe, including the British Isles, in North Africa, throughout the North American continent from Alaska to Mexico, and extensively distributed in Asia, where the deposits of the sub-Himalayan or Sivalik hills, belonging to the earliest Pliocene, are rich in the remains of Elephants of varied form. These species are chiefly known and characterized at present by the teeth, some of which resemble the existing Indian and some the African ’type, but the majority are between the two, and make the distinction between Elephas and Loxodon as different genera quite impracticable. Others again approach so closely in the breadth and coarseness of the ridges and paucity of cementum to Mastodon as to have been placed by some zoologists in that genus. These form the group or subgenus called Stegodon by Falconer.

Among the best known extinct Elephants are E. primigenius, the Mammoth, very closely resembling the existing Indian species, and one of the most recently extinct and extensively distributed (see Mammoth); E. antiquus and E. meridionalis, also found in Britain, as well as in Europe generally, of rather earlier date, and inclining more to the Loxodon type, as also do two species found in the island of Malta, E. mnaidiensis and E. melitensis, the latter the smallest known species of the suborder, sometimes not exceeding 3 feet in height when adult. The Stegodon forms, E. clifti, bombifrons, insignis, and ganesa, are ill from India, which locality would appear, from the abundance of remains and variety of forms, as well as the generalized character of some and the geological horizon (Plio-Miocene) in which the remains are found, to be the earliest habitation of the true Elephants yet discovered. Remains of Elephants of the last-named group have also lately been found in China and Japan. A tusk the dentine of which presents the characters hitherto considered peculiar to the Proboscidca, from Australia, has been lately described by Professor Owen under the name of Notelephas. Mastodon.— Dentition: i p⅛θ, c ⅜, p and m ⅜. Upper incisors very large, as in Elephas ; sometimes with longitudinal bands of enamel, more or less spirally disposed. Lower incisors variable: when present comparatively small and straight, sometimes persistent, sometimes early deciduous, and in some species never present. Grinding surface of molars with transverse ridges, the summits of which are divided more or less into conical or mammillary cusps, and often with secondary or additional cusps between and clustering against the principal ridges; enamel thick; cementum very scanty, never filling up the interspaces between the ridges. The third, fourth, and fifth molars having the same number of ridges, which never exceeds five. In some species {M. ohioticus) no vertical succession has been observed, but in others, as Μ. angustidens, the two posterior premolars, and in the American M. productus apparently all three, are preceded by milk molars. There is also a horizontal succession as in Elephants, the anterior teeth being lost before the posterior ones are fully developed, but not so complete as in the former genus, for as many as three teeth may be in place in one jaw at one time. The skull generally is less elevated and less cellular than in Elephas ; otherwise the remainder of the skeleton is similar.

All known Mastodons are gigantic animals, equalling or exceeding the recent Elephants in size. Their remains have been found in Europe and southern Asia and America, from the Miocene to the Pleistocene epochs.

Dinothérium. — Dentition of adult: i 0 ~ , c ⅜, p ⅜, m ⅜ = 22; all present at the same time, there being no horizontal succession, but the premolars replace milk teeth in the ordinary manner. The presence or absence of upper incisors has not yet been clearly ascertained. Lower incisors, large, conical, descending and slightly curved backwards, implanted in a greatly thickened and deflected beak or prolongation of the symphysis. In section they do not show the decussating striae characteristic of Mastodons and Elephants. Crowns of molars with strong, transverse, crenulated ridges, with deep valleys between, much resembling those of the Tapirs. Ridge formula of the permanent molar series: 2, 2, 3, 2, 2. The three ridges of the first true molar appear to be constant in both upper and lower jaws, although it is quite an anomalous character among Proboscideans for this molar to have more ridges than those which come behind it. The last milk molar has also three ridges, the penultimate but two. The cranium is much depressed, with comparatively little development of air-cells. The remainder of the skeleton is imperfectly known, but apparently agrees in its general characters with that of the other Proboscideans.

Remains of Dinothérium giganteum, an animal of elephantine proportions, strikingly characterized by the pair of huge tusks descending nearly vertically from the front of the lower jaw, were first discovered at Eppelsheim, near Darmstadt, and described by Kaup. They have since been met with in various Middle and Upper Miocene formations in the south of Germany, France, Greece, and Asia Minor. Three species, D. pentapotamiae, D. indicum, and D. sindiense, have been, described by Falconer and Lydekker from north-western India. The genus has hitherto not been found in England or in America.

The genus Phenocodus, from the Lower Eocene of Wyoming, lately described by Cope {Am. Naturalist, December 1881 and June 1882), is placed by that zoologist in a special group called Condylarthra, allied to the Proboscidca, but distinguished by “a post-glenoid process, and a third trochanter of the femur, and no calcaneal facet for the fibula.” This and the Proboscidca are united by Cope to form the order Taxeopoda, one of his primary divisions of the Ungulata.

In all the preceding forms the astragalus articulates only with the navicular bone, in those that follow with both navicular and cuboid.

Suborder AMBLYPODA.

Among the most remarkable of the recent discoveries in the Eocene formations of the western States of North America has been that of a group of animals of huge size, approaching if not equalling that of the largest existing Elephants, presenting a combination of characters quite unlike those known among either recent or extinct creatures, and of which there were evidently many species living contemporaneously, but all of which became extinct before the close of the Eocene period. To form some idea of their appearance, we must imagine animals very elephantine in general proportions and in the structure of their limbs. The fore foot had five, and the hind foot four toes. The tail, as in the Elephants, was long and slender, but the neck, though still short, was not so much abbreviated as in modern Proboscideans, and there is no evidence that they possessed a trunk. The head differed greatly from that of the Elephants, being long and narrow, more like that of a Rhinoceros, and, as in that animal, was elevated behind into a great occipital crest, and it had developed upon its upper surface three pairs of conspicuous, laterally diverging protuberances, one pair in the parietal region, one on the maxillaries in front of the orbits, and one (much smaller) near the fore part of the elongated nasal bones. Whether these were merely covered by bosses of callous skin, as the rounded form and ruggedness of their extremities would indicate, or whether they formed the bases of attachment for horns of still greater extent, like those of the Rhinoceros or of the Cavicorn Ruminants, can only be a matter of conjecture. There were no upper incisors, but three on each side below, of comparatively small size, as was also the lower canine. A huge, compressed, curved, sharp-pointed canine tusk, very similar in form and position to that of the Musk-Deer, descended from each side of the upper jaw. These were present in both sexes, but very much smaller in the female, as was also the flange-like process of the lower jaw by which they were guarded. Behind these, and at some distance from them, were on each side above and below six molar teeth, of comparatively small size, placed in continuous series, each with a pair of oblique ridges conjoined internally and diverging externally in a V-like manner, and provided with a stout basal cingulum. The dental formula was therefore i ⅞, c k, p ⅜, m | = 34; and the dentition had thus already attained a remarkable degree of specialization, although the brain was smaller and more rudimentary in characters than in almost any other known mammal.

The first-discovered evidences of the existence of animals of this group were described by Leidy in 1872, under the name of Uinta-therium (from the Uintah mountains, near which they were found). Other nearly allied forms have been named Dinoceras (restoration of which is shown in fig. 105), Tinoceras, and Loxolophodon. They constitute the order Dinoccrata of Marsh, but are included by Cope in the Amblypoda.

Another interesting form referred to this suborder is Coryphodon, which appears to connect the Proboscidca with the most primitive Perissodactyla, especially Lophiodon. It was first described by Owen in 1846 from a fragment of a jaw from the London Clay. More perfect remains were afterwards discovered in France, and lately in great abundance, indicating many species from the size of a Tapir to that of a Rhinoceros, in the lowest Eocenes of New Mexico and Wyoming, in the United States. It had forty-four teeth; the canines of both jaws were large and sharp-pointed, and the molars had strongly pronounced oblique ridges. The general proportions were those of a Bear, but the tail was of moderate length, and the feet short and wide, with five toes on each.

The Tertiaries of South America have yielded some very remarkable forms of mammalian life, the nature and affinities of which have greatly puzzled all zoologists who have attempted to unravel them. Macrauchenia, an animal with a Camel-like neck, is now known to be a Perissodactyle, though in some characters somewhat aberrant. The articulation of the fibula with the calcaneum is an Artiodactyle or perhaps generalized character. The teeth ally it to Palaeotherium and Rhinoceros. Homalodontotherium, from the banks of the river Gallegos, south-east Patagonia, is known by the teeth alone, which, though very generalized, are on the whole rhinocerotic. Nesodon, from the same locality, also only known by the dentition and some parts of the skull, connects the last and Macrauchenia with Toxodon. These three genera have the typical dental formula of i ⅜, c⅛, p ⅜, m ⅜ = 44. Toxodon is an animal about the size of a Hippopotamus; it was first discovered by Darwin, and many specimens have since been found in Pleistocene deposits near Buenos Ayres, and described by Owen, Gervais, and Burmeister. The teeth consist of large incisors, very small lower canines, and strongly curved molars, all with persistent roots, the formula being apparently i ∣, c ⅜, p ⅜, in f = 38. The cranial characters exhibit a combination of those found in both Perissodactyles and Artiodactyles, but the form of the hinder part of the palate and the absence of an alisphenoid canal belong to the latter; and the tympanic, firmly fixed in between the squamosal and the exoccipital, ankylosed to both, and forming the floor of a long upward-directed meatus auditorius, is so exactly like that of the Suina that it is difficult to believe it does not indicate some real affinity to that group. These characters seem to outweigh in importance those by which some zoologists have linked Toxodon to the Perissodactyla, and the absence of the third trochanter and the articulation of the fibula with the calcaneum tell in the same direction. The structure of the feet is not completely known, but Cope has shown that the tarsal bones differ altogether from those of either Artiodactyles or Perissodactyles, and more nearly resemble those of the Proboscidea than any other known Ungulates.

Mesothorium, also called Typotherium, from the same locality, was an animal rather larger than a Capybar·a, and of much the same general appearance. Its skeleton is completely known, and shows a singular combination of characters, resembling Toxodon or a generalized Ungulate on the one hand, and the Rodents, especially the Leporidae, on the other. In the presence of clavicles it differs from all known Ungulates, and in having four lower incisors from all Rodents. The teeth are i ⅜, c ⅜, p f, in ¾ = 24.

It will thus be seen that, although our knowledge of many of these forms is still very limited, we may trace among them a curious chain of affinities, which would seem to unite the Ungulates on the one hand with the Rodents on the other; but further materials are required before we can establish with certainty so important a relationship, one which, if true, would alter materially some of the prevailing views upon the classification of mammals.

UNGULATA VERA.

In the typical Ungulata the feet are never plantigrade, and the functional toes do not exceed four,—the inner digit being suppressed, at all events in all forms which have existed since the Early Eocene period. The os magnum of the carpus articulates freely with the scaphoid. The allantois is largely developed, and the placenta, so far as is known, is uon-deciduate, the chorionic villi being either evenly diffused or collected in groups or cotyledons (in Pecora) . The testes descend into a scrotum. There is never an os penis. The uterus is bicornuate. The mammae are usually few and inguinal, or may be numerous and abdominal (as in*i⅛⅛α), but are never solely pectoral. The cerebral hemispheres in existing Ungulates are well convoluted.

The group is now, and has been throughout the whole of the Tertiary period, composed of two perfectly distinct sections, differing from each other, not only in the obvious characters of the structure of the limbs, but in so many other parts of their organization that they must be considered as of the rank at least of suborders. The characters of these divisions, first indicated by Cuvier, were thoroughly established by Owen, by whom the names whereby they are now generally known were proposed.

Suborder PERISSODACTYLA.

This is a perfectly well-defined group of Ungulate mammals, represented in the actual fauna of the world by only three distinct types or families—the Tapirs, the Rhinoceroses, and tlιe Horses—poor in genera and species, and (except in the case of the two domesticated species of Equus, which have been largely multiplied and diffused by man’s agency) not generally numerous in individuals, though widely scattered over the earth’s surface. Palaeontological records show very clearly that these are but the surviving fragments of a very extensive and much varied assemblage of animals which flourished upon the earth throughout the whole of the Tertiary geological period, and which, if it could be reconstructed in its entirety, would not only show members filling up structurally the intervals between the existing apparently isolated forms, but would show several marked lines of specialization which have become extinct without leaving any direct successors.

The following are the principal characters distinguishing them from the Artiodactyla. Premolar and molar teeth in continuous series, with massive, quadrate, transversely ridged or complex crowns,—the posterior premolars resembling the true molars in size and structure. Crown of the last lower molar commonly bilobed. Dorso-lumbar vertebrae never fewer than twenty-two, usually twenty-three in the existing species. Nasal bones expanded posteriorly. An alisphenoid canal. Femur with a third trochanter. The middle or third digit on both fore and hind feet larger than any of the others, and symmetrical in itself, the free border of the ungual phalanx being evenly rounded (see fig. 107). This may be the only functional toe, or the second and fourth may be subequally developed on each side of it. In the Tapirs and many extinct forms, the fifth toe also remains on the fore limb, but its presence does not interfere with the symmetrical arrangement of the remainder of the foot around the median line of the third or middle digit. Traces of a hallux have only been found in some extremely ancient and primitive forms. The astragalus, has a pulleylike surface above for articulation into the*tibia, but its distal surface is flattened and unites to a much greater extent with the navicular than with the cuboid, which bone is of comparatively less importance than in the Artiodactyles. The calcaneum does not articulate with the lower end of the fibula. The stomach is simple, the caecum large and capacious, the placenta diffused, and the mammae inguinal.

The very distinct minor groups into which the Perissodactyles are divided in the later periods of the earth’s history are, even by the knowledge already gained of the ancient members of the suborder, so closely united by connected forms that it is difficult to make any satisfactory classification of the whole. This is of course what might be expected, and would probably be the case with all other groups if we knew as much of their past history as we do of that of the Perissodactyles. It is necessary, however, for descriptive purposes to have some arrangement; and perhaps, if not the most natural, the most convenient division (especially as it is chiefly or only by these organs that many are known) is one founded upon the structure of the lower molar teeth. By this character we may make three primary divisions, each of which has a representative at the present time:— (A) those in which the crowns of the lower molars are disposed in transverse ridges, as in the Tapirs; (B) those in which the crowns of the lower molars are formed by a pair of crescents, as in Rhinoceros; (C ’) those in which the crowns of the lower molars are formed of a pair of crescents, with the addition of inner lobes or columns, as in the Horses. As these forms are all modifications of the same essential pattern, transitions in certain or all of the teeth must be expected in many cases, and, as before implied, the grouping of the Perissodactyles into Tapiroid, Rhinocerotic, and Equine sections according to the pattern of their molar teeth may not be a true exposition of the real affinities of the genera, but must be looked upon rather as a convenient provisional arrangement.

A. Tapiroid Section.

Lower molars bilophodont.

Family Lophiodontidae.

Both upper and lower true molars bilophodont. Premolars smaller and simpler than the true molars. Four toes on the anterior and three on the posterior feet. This family includes a large number of more or less imperfectly known forms,' all extinct, ranging from the size of a Rabbit to that of an Ox. They are the earliest in time and most generalized in structure of the known Perissodactyles. It is possible that from some either of the known or the still undiscovered members of this group most of the other types of the order have been derived. Their remains have been found in Europe only in the Lower and Middle Eocene, though in North America they appear to have lingered to a somewhat later date. The genus Hyracotherium was established in 1839 by Owen for a small animal, no larger than a Hare, the skull of which was found in the London Clay at Herne Bay. A more perfect specimen apparently of the same species was afterwards (in 1857) described under the name of Philophus υulpiceps. Closely allied forms from the European continent have been named Pachynolophus and Lophiotherium. These have all the complete dentition, viz., i ⅜, c 1,7? f, τn f = 44. The posterior lower molar has three lobes. The genus Lophiodon (Cuvier, 1822) contains animals of much larger size and later geological period (Middle or Upper Eocene), in which the dentition was so far specialized as to have lost the anterior premolar of both jaws, the formula being i ∣ , c ⅜, p ⅜, m f = 40. The transverse ridges of the upper molars are placed obliquely, the posterior is smaller than the anterior, and they are united by their external borders; those of the mandible are distinct and only connected by a feeble diagonal crest, the last bearing a talon or rudiment of a third lobe. On the premolars the anterior ridge only is developed. Nearly allied was the American genus Hyrachyus, the structure of which is now very completely known from well-preserved remains. The skeleton closely resembles that of the Tapir, though the dentition is more like that of Lophiodon, except that the last lower molar has but two lobes. As many as nine species have been already described, all from the Upper Eocene. Another form from the same deposits, Colonoceras of Marsh, is said to have had an attachment for a dermal horn on each nasal bone. Triplopus, otherwise closely similar to Hyrachyus, wants the fifth digit of the manus, and hence is placed by Cope in a distinct family, Triplopidae. Family Tapiridae.

Both upper and lower true molars bilophodont. Posterior premolars above and below resembling the true molars. This family is connected with the last by the Middle Miocene genus Listriodon. The genus Tapir us, in which as many as three premolars resemble the true molars, and in which the last lower molar has no talon, appears first in the Upper Miocene of Europe, and has continued with scarcely any appreciable change until the present time, being represented by several species in Central and South America, and one in the Malay Peninsula and adjacent islands. It is therefore probably the oldest existing genus of mammals. One of the American species differs from all the others in the great anterior prolongation of the ossification of the mesethmoid cartilage, and has been separated generically by Gill under the name of Elasmognathus. See Tapir. B. Rhinocerotic Section.

Lower molar teeth with the ridges, instead of being transverse, curved in a crescentic manner. The outer extremity of each ridge is curved forwards so that the hinder ridge abuts against the external surface of the ridge in front of it. An unworn lower molar of a Rhinoceros has thus externally two convex areas separated by a vertical groove, and internally two principal sinuses, corresponding to the projections externally. The entrances to these sinuses are bordered by three conical pillars—the first of. comparatively little importance, representing the anterior talon of the Tapir’s tooth, the second, the largest, representing the antero-iuternal principal cusp, and the third the postero-intemal principal cusp. The upper molars of all the animals of this section resemble those of Lophiodon in principle, the transverse ridges being joined by an outer wall and placed obliquely, their inner ends inclining backwards and their posterior surfaces being more or less concave. There are two further chief modifications of this type :—(1) that in which the free edge of the outer wall acquires a strongly zigzag or bi-crescentic character, being deviated inwards opposite each of the principal outer cusps, and outwards at the anterior and posterior angles of the tooth and in the middle between the cusps, as in Palaeotherium ; and (2) that in which the outer wall is greatly developed, and in the main flat or smoothly convex, though with slight elevations and depressions corresponding with those so regular and well-marked in the last section; this is the character of the teeth of Rhinoceros and its allies.

Family Hyracodontidae.

Separated by Cope from the next, and containing the genus Hyracodon of Leidy, a primitive or simple Rhinoceros-like type, from the Lower Miocene of North America, with the full number of teeth, but only three digits on each foot.

Family Rhinocerontidae.

A very extensive group, of which many modifications, forming a gradual series, showing increasing specialization from primitive Lophiodon- ∖ τke animals, have been discovered both in North America and in the Old World. One of the most remarkable of these specializations has been the development of dermal horns over tne nasal bones, either in laterally placed pairs as in some of the early forms, or in the median line, either single or double. In America they all became extinct before the close of the Pliocene period; but in the Old World, although their geographical distribution has become greatly restricted, at least five well-marked species survive. See Rhinoceros. Family Macraüchen’idae.

This contains one extinct genus, Macrauchenia, with two species Μ. palachonica and Μ. l·oliviensis, both from South America, and apparently from Pliocene formations. They are very singular and specialized forms, quite out of the line of descent of any of the existing Perissodactyles, and the steps by which they are connected with the rest of the group have not yet been discovered. Of the larger species, M palachonica, the skeleton is completely known. It had the full number of forty-four teeth, forming an uninterrupted series. The cervical vertebra resemble those of the Camels in the position of the vertebrarterial canal, but the ends of the centra are flat, and not opisthocoelous as in the allied forms. In some of the limb characters it resembles the Equidae, but in the articulation of the fibula with the calcaneum it agrees with the Artiodactyles. The structure of the feet is, however, distinctly Perissodactyle, there being three toes on each.

Families Chalicotheriidae and Menodontidae.

These families, with not very distinctly defined boundaries, contain a large number of extinct forms from Eocene and Miocene formations of both the Old and the New World. Among the latter the most remarkable is a·group of animals of gigantic size, to the first-known fragment of which the name of Menodus was given in 1849 by Pomel, but of which more perfect remains have since been described by Leidy as Titanotherium and MegotMrops, by Marsh as Brontotherium, and by Cope as Symborodon, some of which appear to represent distinct generic modifications, but the synonymy of the group is at present much confused. The head was large and much elongated, as in the Rhinoceros; but they had a pair of stout diverging osseous protuberances like horn-cores on the maxillaries in front of the orbits. Their molar teeth were of a simple palaeotheroid type, and the incisors and canines were very much reduced. Their fore feet had four and their hind feet three short, stout toes. Their remains abound in the Lower Miocene strata of North America.

Family Palaeotheriidae.

The structure of the type of this family, Palaeotherium, was made known by Cuvier, from specimens found in the Paris gypsum beds (Upper Eocene). Fig. 108 gives an idea of its general appearance, not unlike that of a Tapir, which also it resembled in size. It had, however, but three toes on the fore feet. The dentition was i ⅜, c ⅛, p ⅜, m ’ = 44. Many species and allied genera (as Palaplotherium, an earlier form from the Middle Eocene, and Anchitherium, a later one from the Miocene) have been discovered both in Europe and North America. To some of these the ancestral form of the modem Horses may be traced, the transition from this to the next family being formed by almost imperceptible gradations.

G. Equine Section.

Lower molars formed of a pair of crescents complicated by the addition of columns or lobes at the inner extremities. Upper molars a modification of the palaeotheroid type, but gradually passing as time advanced from the brachyodont to the hypsodont form. Outer digits becoming gradually reduced, until, as in the modem Horses, there is but one (the third) functional digit on each foot. To these alone the family Equidae is restricted by some authors, but in few groups is the artificial nature of the boundaries placed between such divisions so apparent as in the Perissodactyles, for the simple reason that their palaeontological history is better known than that of most others, and so many of the intermediate forms have been preserved. For the history, characters, and present distribution of the Equidae, see the article Horse, vol. xii. p. 172 sq. Suborder ARTIODACTYLA.

This is an equally well-defined group, traceable from the Early Eocene period, though then apparently by no means so numerous as the Perissodactyles. Some of its types, as that represented in the existing Swine, have retained to the present time much of the primitive character of the group; but others have been gradually becoming more specialized and more perfected in structure, and its latest modification, the Cavicorn Ruminants or Bovidae (Antelopes, Sheep, and Oxen), are now the dominating members of the great Ungulate order, widespread in geographical range, rich in generic and specific variation, and numerous in individuals, —forming in all these respects a great contrast to such decadent types as those represented by the Tapirs and Rhinoceroses.

The principal anatomical characters by which they are distinguished from the Perissodactyles are as follows. The premolar and molar teeth not alike, the former being single and the latter two-lobed. The last lower molar of both first and second dentition almost invariably three-lobed. Nasal bones not expanded posteriorly. No alisphenoid canal. Dorsal and lumbar vertebrae together always nineteen, though the former may vary from twelve to fifteen. Femur without third trochanter. Third and fourth digits of both feet almost equally developed, and their ungual phalanges flattened on their inner or contiguous surfaces, so that each is not symmetrical in itself, but when the two are placed together they form a figure symmetrically disposed to a line drawn between them. Or, in other words, the axis or median line of the whole foot is a line drawn between the third and fourth digits, while in the Perissodactyles it is a line drawn down the centre of the third digit. Distal articular surface of the astragalus divided into two nearly equal facets, one for the navicular and one for the cuboid bone. The calcaneum with an articular facet for the lower end of the fibula. Stomach almost always more or less complex. Colon convoluted. Caecum small. Placenta diffused or cotyledonary. Mammae few and inguinal, or numerous and abdominal.

In treating of many sections of mammals, it is only from the existing species that our characters and classification can be derived, and to these chiefly our observations upon the group must be directed, the extinct forms being so little known that they can only be referred to incidentally. With the Ungulata, however, it is quite otherwise. As with the last section, the history of the. Artiodactyla throughout the Tertiary period is now well known, and throws great light upon the position and relations of the existing groups.

The principal modifications which have taken place in the tyP e from its earliest known and most generalized manifestation have been the following :— „

1. As regards the teeth. Assumption of the grinding surfaces ot the molar teeth either of a distinctly tubercular (bunodont) or of a crescentic ridged (selenodont) form. Modification of the latter from a brachyodont to a hypsodont type. Loss of upper incisors. Development of canines into projecting tusks. Loss of anterior premolars.

2. As regards the limbs. Reduction of the ulna from a complete and distinct bone to a comparatively rudimentary state in which it coalesces more or less firmly with the radius. Reduction of the fibula till nothing bu,t its lower extremity remains. Reduction and final loss of outer pair of digits (second and fifth), with coalescence of the metapodial bones of the two middle digits. Union of the navicular and cuboid, and sometimes the ectocuneiform bone, of the tarsus.

3. Change of form of the odontoid process of the axis from a cone to a hollow half-cylinder.

4. Development of horns or antlers on the frontal bones, and gradual complication of form of antlers.

5. By inference only, increasing complication of stomach with ruminating function superadded. Modification of placenta from simple diffused to cotyledonary form.

The primitive Artiodactyles, with the typical number (44) of incisor, canine, and molar teeth, brachyodont molars, conical odontoid process, four distinct toes on each foot, with metapodium and all carpal bones discrete, no frontal appendages, and (in all probability) simple stomach and diffused placenta, λvere separated even in the earliest known forms into Bunodonta and Selenodonta, A.. Bunodonta.

This, the most primitive group, with various offsets which became partially specialized and then extinct, unable apparently to adapt themselves to new conditions, has been continued to the present day with comparatively little change in the section of the suborder called Suina, containing the families Hippopotamidae and Suidae. See Hippopotamus, Peccary, and Swine.

B. Selenodonta.

Members of this group having the complete· typical dentition as regards number, but with various modifications in the details of the form of the teeth, and also in the structure of the feet, abounded in the Middle and Upper Eocene and Lower Miocene of Europe and America. One of the earliest known, Anoplotherium, was fully described by Cuvier from remains found in the Paris gypsum beds (Upper Eocene). Its teeth formed a series unbroken by a gap or diastema, and were of uniform height (as in Man alone of existing mammals). Its tail was long, with large chevron bones underneath, not usually found in Ungulates, and there were but two toes on each foot. It was in many respects a much specialized form, apparently not on the line of descent of any of the existing groups. Cheeropotaτnus, Anthracotherium, Hyopotamus, Xiphodon, Dichodon, Dichobune, Cainotherium, the American Oreodon, and numerous others were forms more or less intermediate in character between the three distinct sections into which, by their extinction, the Selenodont Artiodactyles can now be divided,—the Tylopoda, also called Phalangüjrada, the Tragulina, and the Pecora or Cotylophora.

I. Tylopoda.

Represented at the present time by the tVo species of Camels of the Old World and the Llamas of America. For their special distinguishing characters see articles Llama and Camel.

II, Tragulina.

No teeth in premaxillae. Upper canines well-developed, especially in the.males; narrow and pointed. Lower canines incisiform. No .caniniform premolars in either jaw. Molariform teeth in a continuous series consisting of p ⅜, m ∣ . Odontoid process of axis conical. Fibula complete. Four complete toes on each foot. The middle metapodials generally confluent, the outer ones (second and fifth) very slender but complete, i. e. , extending from the carpus or tarsus to the digib Navicular, cuboid, and ectocuneiform bones of tarsus united. Tympanic bullae of skull filled with cancellar tissue. No frontal appendages. Ruminating, but the stomach with only three distinct compartments, the maniplies or third cavity of the stomach of the Pecora being rudimentary. Placenta diffused.

This section contains the single family Tragulidae, containing a few animals of small size, commonly known as Chevrotains, intermediate in their structure between the Deer and the Pigs. The large size of the canines of the male and the absence of horns caused them to be associated formerly with Moschus, one of the true Deer; hence they are often spoken of as “Pigmy Musk-Deer,” although they have no musk-secreting gland, or, except in the above-named trivial external characters, no special affinities with the true Musk. There has scarcely been a more troublesome and obdurate error in zoology than in this association of animals so really distinct. It has been troublesome, not only as preventing a just conception of the relations of existing Artiodactyles, but also in causing great confusion and hindrance in palaeontological researches among allied forms; and most obdurate, inasmuch as all that has been recently done in advancing our knowledge of both groups has not succeeded in eradicating it, not only from nearly every one of our zoological text-books, whether British or Continental, but even from works of the highest scientific pretensions.

The family is now generally divided into two genera.

Tragulus, containing the smallest of the existing Ungulates, animals having more of the general aspects and habits of some Rodents, as the Agoutis, than of the rest of their own order. The best-known species are T. jaυanicus, T. napu, T. kanchil, T. stanleyanus, and T. memmina. The first four are from the Malay Peninsula, or the islands of the Indo-Malayan Archipelago, the last from Ceylon and Hindustan.

Hyomoschus is distinguished chiefly by the feet being stouter and shorter, the outer toes better developed, and the two middle metacarpale not ankylosed together. Its dental formula (as that of Tragulus) is i ⅜< c ⅛, p⅜, τzι⅜ = 34. Vertebrae: C7, D13, L6, S5, C12-13. The only existing species, H. aquaticus (ftg. 111), from the west coast of Africa, is rather larger than any of the

Asiatic Chevrotains, which it otherwise much resembles, but it is said to frequent the banks of streams, and have much the habits of Pigs. It is of a rich brown colour, with back and sides spotted and striped with white. It is evidently the survivor of a very ancient form, as remains of a species only differing in size {H. crassus) have been found in Miocene deposits at Sansan, department of Gers, France.

III. Pecora or Cotylophora.

No premaxillary teeth or caniniform premolars. Upper canines generally absent, though sometimes largely developed. Inferior incisors, three on each side with an incisiform canine in contact with them. Molariform teeth consisting of p f, m ⅜, in continuous series. Auditory bullae simple and hollow within. Odontoid process in the form of a crescent, hollow above. Distal extremity of the fibula represented by a distinct malleolar bone of peculiar shape, articulating with the outer surface of the lower end of the tibia. Third and fourth metacarpals and metatarsals confluent. Outer toes small and rudimentary, or in some cases entirely suppressed; their metapodial bones never complete. Navicular and cuboid bones of tarsus united. Horns or antlers usually present, at least in the male sex. Left brachial artery arising from a common innominate trunk, instead of coming off separately from the aortic arch as in the preceding sections. Stomach with four complete cavities. Placenta cotyledonous.

The Pecora or true Ruminants form at the present time an extremely homogeneous group, one of the best-defined and most closely united of any of the Mammalia. But, though the original or common type has never been departed from in essentials, variation has been very active among them within certain limits; and the great difficulty which all zoologists have felt in subdividing them into natural minor groups arises from the fact that the changes in different organs (feet, skull, frontal appendages, teeth, cutaneous glands, &c.) have proceeded with such apparent irregularity and absence of correlation that the different modifications of these parts are most variously combined in different members of the group. It appears, however, extremely probable that they soon branched into two main types, represented in the present day by the Cervidae and the Bovidae, — otherwise the Antlered and Horned Ruminants. Intermediate smaller branches produced the existing Musk-Deer and Giraffe, as well as the extinct Helladotherium inclining to the first-named group and the extinct Sivatherium, Brahmatherium, Hy- daspüherium and others more allied to the latter, although upon the true relationship of these forms there is a difference of opinion between the two palaeontologists who have paid most attention to the group, Riitimeyer and Lydekker, but the materials forthcoming at present are scarcely sufficient for forming a decided opinion.

The earliest forms of true Pecora, as Gelocus and Dremotherium (Miocene), had no frontal appendages, and some few forms (Moschus and Hydropotes) continue to the present day in a similar case. In the very large majority, however, either in both sexes or in the male only, a pair or occasionally two pairs (Tetraceros and the extinct Sivatherium) of processes are developed as weapons of offence and defence from the frontal bones, these being almost always formed on one or other of two types.

1. “Antlers” are an outgrowth of true bone, covered during their growth with vascular, sensitive integument coated with short hair. In this state they remain permanently in the Giraffe, but in the true Cervidse, when the growth of the antler is complete, the supply of blood to it ceases, the skin dies and peels off, leaving the bone bare and insensible, and after a time, by a process of absorption near the base it becomes detached from the skull and is “shed.” A more or less elongated portion or “pedicle” always remains on the skull, from the summit of which a new antler is developed. In the greater number of existing species of Deer this process is repeated with great regularity at the same period of each year. The antler may be simple, straight, subcylιndrical, tapering and pointed, but more often it sends off one or more branches called “tynes” or “snags.” In this case the main stem is termed the “beam.” Commonly all the branches of the antler are cylindrical and gradually tapering. Sometimes they are more or less expanded and flattened, the antler being then said to be “palmated.” In young animals the antlers are always small and simple, and in those species in which they are variously branched or palmated, this condition is only gradually acquired in several successive annual growths. An interesting parallel has been observed here, as in so many other cases, between the development of the race and that of the individual. The earliest known forms of Deer, those of the Lower Miocene, have no antlers, as in the young of the existing species. The Deer of the Middle Miocene have simple antlers, with not more than two branches, as in existing Deer of the second year. Species occur in the Upper Miocene with three branches to the antlers, but it is not until the Upper Pliocene and Pleistocene times that Deer occur with antlers developed with that luxuriance of growth and beauty of form characteristic of some of the existing species in a perfectly adult state. Among recent Cervidae, antlers are wanting in the genera Moschus and Hydropotes; they are present in both sexes in T arandus (the Reindeer), and in the male sex only in all others.

2. The ‘‘ horns” of the Bovidae consist of permanent, conical, usually curved, bony processes, into which air-cells continued from the frontal sinuses often extend, called “horn-cores,” ensheathed in a case of true horn, an epidermic development of fibrous structure, which grows continuously, though slowly, from the base, and wears away at the apex, but is very rarely shed entire. The only existing species in which such a process occurs regularly and periodically is the American Prong-Buck (Antilocapra), in which the horns also differ from those of all others in being bifurcated. Horns are not present at birth, but begin to grow very soon afterwards. The males of all existing Bovidae possess them, and they are also present (though usually not so fully developed) in the females of all except the genera Portax, Tragelaphus, Procapra, Antilope, Aepyceros, Saiga, Kobus, Cervicapra, Pelea, Nanotragus, Neotragus, and Tetraceros.

Another character by which the different members of the Pecora can be distinguished is derived from the characters of the molar teeth. Although there is nothing in the general mode and arrangement of the enamel folds, or in the accessory columns, absolutely distinctive between the two principal families, existing species may generally be distinguished inasmuch as the true molars of the Cervidae are “brachyodont,” and those of the Bovidae “hypsodont,” i.e., the teeth of the former have comparatively short crowns, which, as in most mammals, take their place at once with the neck (or point where the crown and root join) on a level with or a little above the alveolar border, and remain in this position throughout the animal’s life; whereas in the other forms, the crown being lengthened and the root small, the neck does not come up to the alveolar level until a considerable part of the surface has worn away, and the crown of the tooth thus appears for the greater part of the animal’s life partially buried in the socket. In this form of tooth (which is almost always most developed in the posterior molars of the permanent series), the constituent columns of the crown are necessarily nearly parallel, whereas in the first-described they diverge from the neck towards the free or grinding surface of.the tooth. In the more complete hypsodont form the interstices of the lengthened columnar folds of enamel and dentine are filled up with cementum, which gives stability to the whole organ, and which is entirely or nearly wanting in the short-crowned teeth. The same modification from low to high crowns without essential alteration of pattern is seen in an even still more marked manner in some of the Perissodactyle Ungulates, the tooth of the Horse bearing to that of Anchitherium (see Horse, vol. xii. p. 174) the same relation as that of an Ox does to the early Selenodont Artiodactyles. A parallel modification has been also shown to have taken place in the molar teeth of the Proboscidea (see p. 423).

As the hypsodont tooth is essentially a modification of and, as it were, an improvement upon the brachyodont, it is but natural to expect that all intermediate forms may be met with. Even among the Deer themselves, as pointed out by Lartet, the most ancient have very short molars, and the depressions on the grinding surface are so shallow that the bottom is always visible, while in the Cervidae of the more recent Tertiary periods, and especially the Pleistocene and living species, these same cavities are so deep that whatever be the state of the dentition the bottom cannot be seen. Some existing Deer, as the Axis, are far more hypsodont than the majority of the family; and, on the other hand, many of the Antelopes (as Tragelaphus) retain much of the brachyodont character, which is, however, completely lost in the more modern and highly specialized Sheep and Oxen.

Family Cervidae.

Frontal appendages, when present, in the form of antlers. First molar at least in both jaws brachyodont. Two orifices to the lacrymal duct, situated on or inside the rim of the orbit. An anteorbital vacuity of such dimensions as to exclude the lacrymal bone from articulation with the nasal. Upper canines usually present in both sexes, and sometimes attaining a very great size in the male (see fig. 114). Lateral digits of both fore and hind feet almost always present, and frequently the distal ends of the metapodals. Placenta with few cotyledons. Gall-bladder absent (except in Moschus). This family contains numerous species, having a wide geographical distribution, ranging in the New World from the Arctic Circle as far south as Chili, and in the Old World throughout the whole of Europe and Asia, but absent in the Ethiopian and Australian regions. For the characters of the generic subdivisions and their distribution, see Stag, also Deer, Muntjac, and Musk-Deer. Family Camelopardalidae.

Frontal appendages consisting of a pair of short, erect, permanent bony processes, ossified from distinct centres, and for a time suturally connected with the frontals, though afterwards ankylosed to them, covered externally with a hairy skin, present in both sexes, and even in the new-born animal. Anterior to these is a median protuberance on the frontal and contiguous parts of the nasal bones, which increases with age, and is sometimes spoken of as a third horn. No upper canines. Molars brachyodont. Lateral digits entirely absent on both fore and hind feet, even the hoofs not developed.

This family contains but a single species, the well-known and very remarkable animal the Giraffe, or Camelopard (Camelopardalis giraffa). See Giraffe. Family Bovidae.

Frontal appendages when present in the form of horns. Molars usually hypsodont. Usually only one orifice to the lacrymal canal, situated inside the rim of the orbit. Lacrymal bone almost always articulating with the nasal. Canines absent in both sexes. The lateral toes may be completely absent, but more often they are represented by the hoofs alone, supported sometimes by a very rudimentary skeleton, consisting of mere irregular nodules of bone. Distal ends of the lateral metapodals never present. Gall-bladder almost always present. Placenta with many cotyledons.

The Bovidae, or hollow-horned Ruminants (Cavicornia), form a most extensive family, with members widely distributed throughout the Old World, with the exception of the Australian region; but in America they are less numerous, and confined to the Arctic and northern temperate regions, no species being indigenous either to South or Central America. There is scarcely any natural and well-defined group in the whole class which presents greater difficulties of subdivision than this; consequently zoologists are as yet very little agreed as to the extent and boundaries of the genera into which it should be divided. The principal species will be found more particularly described under the headings Antelope, Bison, Buffalo, Cattle, Chamois, Eland, Gnu, Goat, Hartebeest, Ibex, Musk-Ox, Nylghau, Ox, Saiga, and Sheep. Group TILLODONTIA.

Here may be noticed a remarkable group of animals, called by Marsh Tillodontia, the remains of which are found abundantly in the Lower and Middle Eocene beds of North America. They seem to combine the characters of the Ungulata, Rodentia, and Carnivora. In the genus Tillotherium of Marsh (probably identical with the previously described Anchippodus of Leidy) the skull resembled that of the Bears, but the molar teeth were of the Ungulate type, while the large incisors were very similar to those of the Rodents. The skeleton resembled that of the Carnivores, but the scaphoid and lunar bones were distinct, and there was a third trochanter on the femur. The feet were plantigrade, and each had five digits, all with long pointed claws. In the allied genus Stylinodon all the teeth were rootless. Some were as large as a Tapir.

These, with other similar animals, constituting a group called Taeniodonta, are included by Cope in his large order Bunotheria, to which also the existing Insectivora are referred. The constantly increasing knowledge of these annectant forms adds to the difficulty so often referred to in this article of establishing anything like a definite classification of the heterodont mammals.

Order CARNIVORA.

Though the Carnivora as at present restricted form a very natural and well-defined order among the Mammalia, it is difficult to find any important common diagnostic characters by which they can be absolutely separated; but, as in the case of so many other natural groups, it is by the possession of a combination of various characters that they must be distinguished. They are unguiculate, and have never less than four well-developed toes on each foot, with nails more or less pointed, rarely rudimentary or absent. The pollex and hallux are never opposable to the other digits. They are regularly diphyodont and heterodont, and their teeth are always rooted. Their dentition consists of small pointed incisors, usually three in number, on each side of each jaw, of which the first is always the smallest and the third the largest, the difference being most marked in the upper jaw; strong conical, pointed, recurved canines; molars variable, but generally, especially in the anterior part of the series, more or less compressed, pointed, and trenchant; if the crowns are flat and tuberculated they are never complex or divided into lobes by deep inflexions of enamel. The condyle of the lower jaw is a transversely placed half-cylinder working in a deep glenoid fossa of corresponding form. The brain varies much in relative size and form, but the hemispheres are never destitute of well-marked convolutions. The stomach is always simple and pyriform. The caecum is either absent or short and simple, and the colon is not sacculated or greatly wider than the small intestine. Vesiculae seminales are never present. Cowper’s glands are present in some, absent in other groups. The uterus is bicornuate. The mammae are abdominal, and very variable in number. The placenta is deciduate, and almost always zonary. The clavicle is often entirely absent, and when present is never complete. The radius and ulna are distinct. The scaphoid and lunar bones are always united into one, and there is never a distinct os centrale in the adult. The fibula is always a distinct slender bone.

The large majority of the species composing this order subsist chiefly upon some variety of animal food, though many are omnivorous, and some few chiefly, though not entirely, vegetable eaters. The more typical forms live altogether on recently-killed warm-blooded animals, and their whole organization is thoroughly adapted to a predaceous mode of life. In conformity with this manner of obtaining their subsistence they are generally bold and savage in disposition, though some species are capable of being domesticated, and when placed under favourable circumstances for the development of such qualities exhibit a very high degree of intelligence and fidelity. The order is naturally divided into two suborders, the members of one being the more typical, and mainly terrestrial in their mode of life, while those of the other are aberrant, having the whole of their organization specially modified for living habitually in water. These are called respectively the True or Fissiped and the Pinniped Carnivora. Suborder CARNIVORA VERA or FISSIPEDIA.

Generally adapted for terrestrial progression and mode of life, though some may be partially aquatic in their habits. The fore limbs never have the first digit, or the hind limbs the first and fifth digits, longer than the others. Incisors J on each side, with very rare exceptions. Cerebral hemispheres more or less elongated; always with three or four gyri on the outer surface forming arches above each other, the lowest surrounding the Sylvian fissure. The molar series of teeth have not the uniform characters of those of the Pinnipedia. There is always one tooth in each jaw which is specially modified, and to which the name of “sectorial” or “carnassial” tooth has been applied. The teeth in front of this are more or less sharp-pointed and compressed; the teeth behind it are broad and tuberculated. The characters of the sectorial teeth deserve special attention, as, though fundamentally the same throughout the suborder, they are greatly modified in different genera. The upper sectorial is the most posterior of the teeth which have predecessors, and is therefore reckoned as the last premolar (p 4 of the typical dentition). It consists essentially of a more or less compressed blade supported on two roots and an inner lobe supported by a distinct root (see fig. 116). The blade when fully developed has three cusps (1, 2, and 3), but the anterior is always small, and often absent. The middle lobe is conical, high, and pointed; the posterior lobe has a compressed straight knife-like edge. The inner lobe (4) varies very much in extent, but it is generally placed near the anterior end of the blade, though sometimes it is median in position.

In the ^Ursidx alone both inner lobe and root are wanting, and there is often a small internal and posterior cusp (5) without root. In this aberrant family also the sectorial is relatively to the other teeth much smaller than in the rest of the Carnivora. The lower sectorial (see fig. 117) is the most anterior of the teeth without predecessors in the milk series; it is therefore reckoned the first true molar (m 1). It has two roots supporting a crown, consisting when fully developed of a compressed bilobed blade (1 and 2), a heel (4), and an inner tubercle (3). The lobes of the blade, of which the hinder (2) is the larger, are separated by a notch, generally prolonged into a linear fissure. In the most specialized Carnivora, as the Felidae (I.), the blade alone is developed, both heel and inner tubercle being absent or rudimentary. In others, as Meles (V.) and Ursus (VI.), the heel is greatly developed, broad, and tuberculated. The blade in these cases is generally placed obliquely, its flat or convex (outer) side looking forwards, so that the two lobes are almost side by side, instead of anterior and posterior. The inner tubercle (3) is generally a conical pointed cusp, placed to the inner side of the hinder lobe of the blade. The special characters of these teeth are more disguised in the Sea Otter {Enhydra) than in any other form, but even in it they can be traced.

The toes are nearly always armed with large, strong, curved, and tolerably sharp claws, ensheathing the ungual phalanges, and held more firmly in their places by broad laminae of bone reflected over their attached ends from the bases of the phalanges. In some forms, most notably the Felidae, these claws are “retractile.” The ungual phalanx, with the claw attached, folds back in the fore foot into a sheath by the outer or ulnar side of the middle phalanx of the digit, being retained in this position when the animal is at rest by a strong elastic ligament. In the hind foot the ungual phalanx is retracted on to the top, and not the side of the middle phalanx. By the action of the deep flexor muscles, the ungual phalanges are straightened out, the claws protruded from their sheath, and the soft “velvety” paw becomes suddenly converted into a most formidable weapon of offence. The habitual retraction of the claws preserves their points from wear in ordinary progression.

The Fissipedal Carnivora were divided by Cuvier into two groups, according to the position of the feet in walking,— the Plantigrada, or those that place the whole of the soles to the ground, and the Digitigrada, or those that walk only on the toes; and the difference between these groups was considered of equal importance to that which separated from them both the Pinnigrada or Seals. The distinction is, however, quite an artificial one, and every intermediate condition exists between the extreme typical plantigrade gait of the Bears and the truly digitigrade walk of the Cats and Dogs; in fact, the greater number of the Carnivora belong to neither one form nor the other, but may be called “subplantigrade,” often when at rest applying the whole of the sole to the ground, but keeping the heel raised to a greater or less extent when walking.

A more natural classification is into three distinct sections, of which the Cats, the Dogs, and the Bears may be respectively taken as representatives, and which are hence called Aeluroidea, Cynoidea, and Arctoidea. This division is founded mainly on characters exhibited by the base of the skull, but is corroborated by the structure of other parts. The presence or absence of a bridge of bone, covering the external carotid artery in a part of its course by the side of the alisphenoid bone, and enclosing the “alisphenoid canal,” a character to which the late Mr H. N^. Turner first drew attention, might seem unimportant at first sight, but it is curiously constant in certain groups, which we have other reasons, derived often from a combination of less easily definable characters, to regard as natural. It is therefore generally mentioned in the following family definitions.

Section Aeluroidea.

The Aeluroidea or Cat-like forms include the Felidae, Viverridae, Protelidae, and Hyaenidae. Family Felidae.

True molars reduced to one above and below, that of the upper jaw very small and transversely extended. Only two inferior premolars. Auditory bulla not externally constricted, but internally divided by a septum. No alisphenoid canal. Carotid canal very minute. Digits 5-4. Dorsal vertebra 13.

Felis. — The whole structure of the animals of this genus exhibits the carnivorous type in its fullest perfection. Dentition: i ⅜, c B p ⅜, m, ⅜=∣; total 30. The upper anterior premolar, always small, may sometimes be absent without any other modification in the dental or other structures. Such a variation should not therefore be considered as of generic importance. Incisors very small. Canines large, strong, slightly recurved, with trenchant edges and sharp points, and placed wide apart. Premolars compressed and sharp-pointed. The most posterior in the upper jaw (the sectorial) a very large tooth, consisting of a subcompressed blade, divided into three unequal cusps supported by two roots, with a very small inner lobe placed near the front end of the tooth and supported by a distinct root. The upper true molar a very small tubercular tooth placed more or less transversely at the inner side of the hinder end of the last. In the lower jaw the true molar (sectorial) reduced to the blade alone, which is very large, trenchant, and much compressed, divided into two snbequal lobes. Occasionally it has a rudimentary heel, but never an inner tubercle. The skull generally is short and rounded, though proportionally more elongated in the larger forms. The facial portion is especially short and broad, and the zygomatic arches very wide and strong. The auditory bullae are large, rounded, and smooth. Vertebra: C 7, D 13, I. 7, S 3, C 13-29. Clavicles better developed than in other Carnivora, but not articulating with either the shoulder bones or sternum. Limbs digitigrade. Anterior feet with five toes, the third and fourth nearly equal and longest, the second slightly and the fifth considerably shorter; the pollex still shorter, not reaching as far as the metacarpo-phalangeal articulation of the second. Hind feet with only four toes. The third and fourth the longest, the second and fifth somewhat shorter and nearly equal; the hallux represented only by the rudimentary metatarsal bone. The claws all very large, strongly curved, compressed, very sharp, and exhibiting the retractile condition in the highest degree. The tail varies greatly in length, being in some a mere stump, in others nearly as long as the body. Ears of moderate size, more or less triangular and pointed. Eyes rather large. Iris very mobile, and with a pupillary aperture which contracts under the influence of light in some species to a narrow vertical slit, in others to an oval, and in some to a circular aperture. Tongue thickly covered with sharp-pointed, recurved horny papillae. Caecum small and simple.

As in structure so in habits, the Cats may be considered the most specialized of all the Carnivora. All the known members of the genus feed, in the natural state, almost exclusively on warm-blooded animals which they have themselves killed. One Indian species (F. vivcrrina} is said to prey on fish and even freshwater molluscs. Unlike the Dogs, they never associate in packs, and rarely hunt their prey in open ground, but from some place of concealment wait until the unsuspecting victim comes within reach, or with noiseless and stealthy tread, crouching close to the ground for concealment, approach near enough to make the fatal spring. In this manner they frequently attack and kill animals considerably exceeding their own size. They are mostly nocturnal, and the greater number, especially the smaller species, more or less arboreal. None are aquatic, and all take to the water with reluctance, though some may habitually haunt the banks of rivers or pools, because they more easily obtain their prey in such situations. The numerous species of the genus are very widely diffused over the greater part of the habitable world, though most abundant in the warm latitudes of both hemispheres. No species are, however, found in the Australian region, or in Madagascar. Although the Old-World and New-World Cats (except perhaps the Northern Lynx) are all specifically distinct, no common structural character has been pointed out by which the former can be separated from the latter. On the contrary, most of the minor groups into which the genus has been divided have representatives in both hemispheres.

Notwithstanding the considerable diversity in external appearance and size between different members of this extensive genus, the structural differences are but slight, and so variously combined in different species that the numerous attempts hitherto made to subdivide it are all unsatisfactory and artificial. The principal differences are to be found in the form of the cranium, especially of the nasal and adjoining bones, the completeness of the bony orbit posteriorly, the development of the first upper premolar and of the inner lobe of the upper sectorial, the length of the tail, the form of the pupil, and the condition and coloration of the fur, especially the presence or absence of tufts or pencils of hair on the external ears. There is one decidedly aberrant form, which enables us to divide the genus into two sections, to which the rank of genera is sometimes accorded.

1. Felis proper.—A distinctly cusped inner lobe to the upper sectorial tooth. Claws completely retractile. There are about fifty species, of which the following are the most important and best known.

A. Old-World Species.

For F. leo, see Lion; and for F. tigris, see Tiber. With regard to F. pardus, the Leopard or Panther, it is still a matter of uncertainty whether the large spotted Cats to which these names are given, found chiefly in wooded districts through nearly the whole of Africa and the warmer parts of Asia as far as Japan, belong to one or several species. See Leopard. F. unda, the Ounce, inhabits the highlands of Central Asia, from the snowy mountains of Tibet to the southern parts of Siberia, at altitudes of from 9000 to 18,000 feet above the sea. It is about the size of the common Leopard, but lighter in colour, with longer fur and less distinct spots. Its skull differs in shape from that of all the other Felidae, the facial portion being very broad, the nasal bones especially being wide and depressed, and the zygomatic arches very strong and deep. F. macrocelis, the Clouded Tiger, is a beautifully marked species, with elongated head and body, long tail, and rather short limbs. The canine teeth are proportionally longer than in any existing member of the genus. It is thoroughly arboreal, and is found in the forests of south-east Asia and the islands of Sumatra, Java, Borneo, and Formosa. F. serval, the Serval, from South Africa, is yellow with black spots, and has a short tail and large ears. Numerous smaller species called Tiger Cats and Wild Cats, many of them by no means clearly defined zoologically, are found throughout the warmer parts of Asia and Africa. The Wild Cat of Europe, F. catus, still inhabits the mountainous and wooded parts of Great Britain. The Domestic Cat is an introduced species, and generally supposed to be derived from F maniculata of Egypt and Syria. Moderate-sized Cats, with short tails, rather long limbs, especially the hinder ones, and tufts or pencils of hair on their ears, are called Lynxes. See Lynx.

B. New-World Species. F. concolor, the Puma or Couguar, commonly called ‘ ‘ Panther” in the United States, is about'the size of a Leopard, but of an uniform brown colour, spotted only when young, and is extensively distributed in both North and South America, ranging between the parallels of 60° N. and 50° S. F. onca, the Jaguar, is a larger and more powerful animal than the last, and more resembles the Leopard in its colours. It also is found in both North and South America, but with less extensive range, reaching northwards only as far as Texas, and southwards nearly to Patagonia. See Jaguar. F. pardalis, and several allied smaller elegantly-spotted species inhabiting the intratropical regions of America, are commonly confounded under the name of Ocelot or Tiger Cat. F. yaguarundi, rather larger than the Domestic Cat, with an elongated head and body, and of a uniform brownish-grey colour, ranges from Matamoras to Paraguay. F. eyra is a small Cat, very Musteline in form, having an elongated head, body, and tail, and short limbs, and is also of a uniform light reddish-brown colour. It is a native of South America and Mexico. F. pajeros is the Pampas Cat. Four species of Lynx are described from North America, but it is doubtful whether these are specifically distinct from each other and from the Lynx of northern Europe.

2. Cynaelurus. —Sometimes considered as a distinct genus. The Cheetah or Hunting Leopard, F.jubata, is distinguished fromtheother Felidae by the inner lobe of the upper sectorial, though supported by a distinct root, having no salient cusp upon it, by the tubercular molar being more in a line with the other teeth, and by the claws being smaller, less curved, and less completely retractile, owing to the feebler development of the elastic ligaments. The skull is short and high, with the frontal region broad and elevated in consequence of the large development of the frontal air-sinuses. The head is small and round, the body light, the limbs and tail long. Its colour is pale yellowish-brown with small black spots. The Cheetah is less savage and more easily tamed than most of the Cats. In Asia it has been trained for the chase of the Antelope. It has rather an extensive geographical range from the Cape of Good Hope, throughout Africa and the south-western parts of Asia, as far as southern India.

Fossil Felidae. — Numerous extinct species of the genus are found in Pleistocene, Pliocene,and even later Miocene deposits in Europe, Asia, and America. Among them is the Cave Lion, F. spelaea, which can scarcely be separated specifically from F. leo, and of which abundant remains are found in caves in England and other parts of Europe. F. cristata, from the Siwalik Hills, intermediate in size between a Tiger and Jaguar, is distinguished from the other Felidae by the shortness of the face as compared with the cranial part of the skull. These and many others, mostly of smaller size, present no greater modifications of form than the various existing members of the genus Felis, and can therefore be properly included within its limits; but numerous other forms are gradually becoming known, especially through the researches of American palaeontologists, which, though evidently animals of the same general type and therefore to be included in the family Felidae, depart so much in various details of structure that they must be placed in different genera. As one of the points in which Felis manifests its specialization is the reduction of the number of the molar series of teeth with concomitant shortening of the jaws, it might be supposed that in the earlier and perhaps ancestral forms these teeth would be more numerous and approach more nearly to the primitive or typical number of the heterodont mammals, viz., seven on each side. This is actually the case. One European form (also recently found in America) to which Gervais has given the name of Pseudaelurus, of Miocene age, has the dentition of Felis with an addition of one premolar in the lower jaw; but others have a still larger number, as Archaelurus debilis of Cope from the American Miocene, about the size of a Panther, which has four premolars and a tubercular molar in the upper jaw, and three premolars and two molars in the lower jaw. A tubercular molar in the lower jaw, behind the sectorial, also occurs in Aelurogale, Dinictis, and Nimravus. Another tendency to generalization is the existence in some forms, as Hoplophoneus, of a posterior lobe or heel to the inferior sectorial, found in nearly all Carnivores except the existing Felidae. On the other hand some of the extinct Felidae show a most remarkable tendency towards a specialization not occurring in any of the surviving members of the family, viz., an enormous development of the upper canines, with which is usually associated an expansion downwards and flattening of the anterior part of the ramus of the lower jaw, on the outer side of which the canine lies, when the mouth is closed. In Smilodon naeogeus, the Sabre-toothed Tiger, from the caves of Brazil and also from Pleistocene deposits near Buenos Ayres, an animal about the size of a Tiger, these teeth are 7 inches in length, greatly compressed, and finely serrated on the trenchant anterior edges. Similar serrations are seen on a much fainter scale in the unworn teeth of modern Tigers. Manymodificationsof this commonly-called “machaerodont” type have been met with both in the Old and New World to which the names of Machaerodhs, Drepanodon, Smilodon, Hoplophoneus, Dinictis, Pogonodon, &c., have been given. A very remarkable form, Eusmilus, differs from all other known Felines in having only four incisors in the lower jaw, and a pair of small canines separated by a very long diastema from the next teeth, which consist only of one premolar and one sectorial true molar. The lower jaw is enormously expanded towards the symphysis to protect the large upper canines. This animal then, although of Eocene age, appears to form the culminating development of the sabre-toothed or machaerodont dentition, the most specially carnivorous type of structure known.

Cope divides all the known Feline animals into two families, Felidae and Nimravidae, distinguished by the characters of the foramina at the base of the cranium, the former being of more modern origin than the latter, the members of which are all extinct, and which seem to connect the Cats with still more primitive types of Carnivora. Family Viverridae.

Premolars f or∣. Molars ⅛ or ⅜. Auditory bulla externally constricted, and divided by a septum. An alisphenoid canal (with very rare exceptions). Carotid canal distinct as a groove on the side of the bulla. Digits usually 5-5, but sometimes the pollex or hallux or both may be wanting. Dorsal vertebrae 13 or 14. Limited in distribution to the Old World.

The subfamily Cryptoproctinεe contains the single genus Cryptoprocta. Dentition: i ⅜, c ⅜, p f, m ⅜ = ⅜; total 36. The teeth generally closely resemble those of the Felidae. The first premolar of both jaws is very minute and early deciduous. The upper sectorial has a very small inner lobe, quite at the anterior part of the tooth. The true molar is very small and placed transversely. The lower sectorial has a large trenchant bilobed blade, and a very minute heel, but no inner tubercle. Skull generally like that of Felis, but proportionately longer and narrower. Orbit widely open behind. Vertebrae: C 7, D 13, I. 7, S3, C 29. Body elongated. Limbs moderate in size. Feet subplantigrade; five well-developed toes on each, with sharp, compressed, retractile claws. Ears moderate. Tail long and cylindrical.

The only known species, C. ferox, the “Foussa” of the Malagasy, is peculiar to Madagascar, being the largest carnivorous animal in the island. It is about twice the size of the common Cat (5 feet from nose to end of tail), with short close fur of nearly uniform pale brown. Little is as yet known of its habits, except that it is nocturnal, frequently attacks and carries off goats, and especially kids, and shows great ferocity when wounded, on which account it is much dreaded by the natives.

The remaining numerous specific and generic modifications found in the existing animals belonging to this family seem to group themselves mainly into two tolerably distinct groups, distinguishable by the characters of the auditory bulla and neighbouring parts of the base of the skull, and by the structure of the feet. The one form has the genus Viverra or Civet Cats for its most typical representative, and the other Herpestes or the Ichneumons.

Subfamily Viverrinse.—Auditory bulla oval or rather conical, broad and truncated and not everted behind, narrow in front and more or less compressed at the sides. The outer or anterior chamber very small and flat. The meatus with scarcely any inferior lip, its orifice being close to the tympanic ring. Paroccipital process triangular, its apex projecting slightly beyond the bulla. Claws strongly curved and more or less retractile.

Viverra. — Dentition: if, c ⅛, p ⅜, ∞f=⅜f; total 40. Skull elongated; facial portion small and compressed. Orbits well-defined but incomplete behind. Vertebrae: C 7, D 13, I. 7 (or D 14, I. 6), S 3, C 22-30. Body elongated and compressed. Head pointed in front; ears rather small. Extremities short. Feet small and rounded. Toes short, five on each foot. First toe both on fore and hind feet much shorter than the others. Palms and soles covered with hair, except the pads of the feet and toes, and in some species a narrow central line on the under side of the sole, extending backwards nearly to the heel. Tail moderate or long. A pair of large glandular follicles situated on the perineum (in both sexes), and secreting in most species an oily substance of a peculiarly penetrating odour.

The numerous species of this genus form a large series, the two extremes of which differ considerably, but the several sections into which they may be divided blend so into one another that it is difficult to differentiate them sharply. (1) Viverra proper. This includes the largest species. The teeth are stouter and less compressed than in the other sections. The second upper molar especially larger. The auditory bulla smaller and more pointed in front. Body shorter and stouter; limbs longer; tail shorter, tapering. Under side of tarsus completely covered with hair. Claws longer and less retractile. Fur rather long and loose, and in the middle line of the neck and back especially elongated so as to ⅛orm a sort of crest or mane. Pupil circular when contracted. Perineal glands greatly developed. These characters apply especially to V. civetta, the African Civet, or ‘ ‘ Civet Cat” as it is commonly called, an animal rather larger than a common Fox, and an inhabitant of intratropical Africa. V. zibetta, the Indian Civet, of about equal size, approaches in many respects, especially in the characters of the teeth and feet and absence of the crest of elongated hair on the back, to the next section. It inhabits Bengal, China, the Malay Peninsula, and adjoining islands. V. tangalunga is a smaller but nearly allied animal from the same part of the world. From these three species and the next the civet of commerce, once so much admired as a perfume in England, and still largely used in the East, is obtained. The animals are kept in cages, and the odoriferous secretion collected by scraping the interior of the perineal follicles with a spoon or spatula. (2) Viverricula. This section resembles generally the next, but with the whole of the under side of the tarsus hairy. Alisphenoid canal generally absent. V. malaccensis, the Rasse, inhabiting India, China, Java, and Sumatra, is an elegant little animal, which affords a favourite perfume to the Javanese. (3) Genetta. The Genettes are smaller animals, with more elongated and slender bodies, and shorter limbs than the Civets. Skull elongated and narrow. Auditory bulla large, elongated, rounded at both ends. Teeth compressed and sharp-pointed; a lobe on the inner side of the third upper premolar not present in the previous section. Pupil contracting to a linear aperture. Tail long, slender, ringed. Fur short and soft, spotted or cloudy. Under side of the tarso-metatarsus with a narrow longitudinal bald streak. V. genetta, the common Genette, is found in France south of the river Loire, Spain, south-western Asia, and Africa from Barbary to the Cape. V. felina, senegalensis, tigrina, and pardalis are other named species, all African in habitat. (4) Fossa. V. fossa, from Madagascar, may belong to a distinct section or genus, but its structure is very imperfectly known. (5) In some of the smallest species the second upper molar (already reduced to very small dimensions in the Genettes) is absent; in other respects their dentition agrees with section 3. V. gracilis and V. pardicolor, both from southern Asia, constitute the genus Prionodon of Horsfield; V. τichardsonii, from West Africa, the genus Poiana of Gray. The former has the back of the tarsus hairy, the latter has a narrow naked streak as in the Genettes.

All the animals of this genus are, for their size, extremely active, fierce, and rapacious. They feed chiefly on small mammals and birds.

Arctictis.— Dentition: i f, c -}, p J, wι ∣ = jf; total 40. The posterior upper molar and the first lower premolar very often absent. Molar teeth generally small and rounded, with a distinct interval between every two, but formed generally on the same pattern as Parodoxurus. Vertebrae: C 7, D 14, I. 5, S 3, C 34. Body elongated. Head broad behind, with a small pointed face. Whiskers long and numerous. Ears small, rounded, but clothed with a pencil of long hairs. Eyés small. Limbs short. Soles and palms broad, entirely naked. Tail very long and prehensile. Fur long and harsh. Caecum extremely small. But one species is known, A. binturong, the Binturong, an inhabitant of southern Asia from Nepal through the Malay Peninsula to the islands of Sumatra and Java. Although structurally agreeing closely with the Paradoxures, its tufted ears, long, coarse, and dark hair, and prehensile tail give it a very different external appearance. It is slow and cautious in its movements, chiefly if not entirely arboreal, and appears to feed on vegetable as well as animal substances.

Paradoxurus.— Dentition: i f, c ⅛, p ⅜, m ⅜=⅜⅞j total 40. The blunt and rounded form of the cusps of the hinder premolar and the molar teeth distinguishes this genus from most of the members of the family. Vertebrae: C 7, D 13, I. 7, S 3, C 29-36. Head pointed in front. Ears small, rounded. Body long. Limbs moderate. Palms and soles almost entirely naked. Claws completely retractile. Tail long, non-prehensile. The Paradoxures or Palm-Civets are less strictly carnivorous than the other members of the family. They are mostly about the size of the common Cat, or rather larger, and are partly arboreal in their habits. The species are rather numerous, and present considerable variations in the details of the form and size of their molar teeth. They are restricted geographically to southern Asia and the Indo-Malayan archipelago. The best known species are P. bondar, P. zeylanicus, P. typus, P. musanga, P. larvata, and P. grayi. P. virgata has been separated from the others, and raised into a distinct genus, Arctogale, on account of the smallness of the teeth and the elongation of the bony palate. Otherwise it seems not to differ from the others.

Nandinia contains one species, N. binotata, a somewhat aberrant Paradoxure, from West Africa. It is rather smaller than the true Paradoxures, has smaller and more pointed molar teeth, and no caecum. The wall of the inner chamber of the auditory bulla remains through life unossified.

Hemigalea, another modification of the Paradoxure type, contains one species, H. hardwickii, from Borneo, an elegant-looking animal, smaller and more slender than the Paradoxures, of light grey colour, with transverse broad dark bands across the back and loins.

Cynogale also contains one species, C. bennettii, Gray (described by S. Miiller under the name of Potamophilus barbatus), from Borneo. This is a curious Otter-like modification of the Viverrine type, having semi-aquatic habits, both swimming in the water and climbing trees, living upon fish, Crustacea, small mammals, birds, and fruit. The number and general arrangement of its teeth are as in Paradoxurus, but the premolars are peculiarly elongated, compressed, pointed, and recurved, somewhat as in the Seals, though the molars are tuberculated. Thé head is elongated, the muzzle broad and depressed. Whiskers very long and abundant. Ears small and rounded. Toes short and slightly webbed at the base. Tail short, cylindrical, covered with short hair. Fur very dense and soft, of a dark brown colour, mixed with black and grey.

Subfamily Herpestinae.—Auditory bulla very prominent, and somewhat pear-shaped, the posterior chamber being large, rounded, and generally with its greatest prominence to the outer side. The anterior chamber considerably dilated, and produced into a short inferior wall to the auditory meatus, in which is a depression or vacuity just below the centre of the opening of the meatus. Sometimes this vacuity is continued into the meatus, forming a narrow fissure. The paroccipital process does not project beyond the bulla, but is spread out and lost (in adult animals) on its posterior surface. Toes straight; claws lengthened, exserted, non-retractile.

Herpestes.— Dentition: i f, c ∣ , p ⅛, sometimes f, m ⅜; 40 or 36. Teeth of molar series generally with strongly-developed, sharply-pointed cusps. Skull elongated, constricted behind the orbits. Face short and compressed. Frontal region broad and arched. Postorbital processes of frontal and malar bones well-developed, generally meeting so as to complete the circle of the orbit behind. Vertebrae: C 7, D 13, I. 7, S3, C 2R26. Head pointed in front. Ears short and rounded. Body very long and slender. Extremities short. Five toes on each foot, the first, especially that on the hind foot, very short. Toes free, or but slightly palmated. Palms naked. Distal portion of soles naked, under surface of tarsus and metatarsus clothed with hair. Tail long or moderate, generally thick at the base, and sometimes covered with more or less elongated hair. The longer hairs covering the body and tail almost always annulated. This genus contains a very large number of animals commonly called Ichneumons, or in India Mongooses, varying in size from that of a large Cat down to a Weasel. They are widely distributed over the African continent and the southern parts of Asia, especially India and the Indo-Malayan archipelago, one species occurring also in Spain. They are mostly terrestrial in their habits, feeding on small mammals and birds, reptiles, especially snakes, eggs of birds and reptiles, and also insects. Some species are partially domesticated, being used to keep houses clear of rats, mice, and snakes. H. ichneumon was a sacred animal to the ancient Egyptians. They vary considerably in appearance, some, as H. galera (also called paludinosus and robustus), are larger and heavier, with stouter body, longer limbs, and stronger teeth. Others are small, with very elongated bodies and short legs. The tail also varies somewhat in length, and in the amount of hair with which it is covered. These trivial differences have given rise to the formation by some zoologists of very numerous genera, the characters of which are by no means clearly defined, but the following are the most distinct and generally recognized.

Helogale, premolars ∣, contains two small South-African species, H. parvula and H. undulata. Bdeogale contains also two small Ichneumon-like animals, B . crassicauda and puisa, differing from Herpestes proper in having •only four toes on each foot, both pollex and hallux being absent. The orbit is nearly complete, the tail of moderate length and rather bushy.

Cynictis.— Pollex present, but hallux absent. Skull shorter and broader than in Herpestes, rather contracted behind the orbits, which are large and complete behind. Face short. Anterior chamber of the auditory bulla very large. Front claws elongated.

C . penicillata, from South Africa.

All the foregoing Herpestines have the nose short, with its under surface flat, bald, and with a median longitudinal groove. The remaining forms have the nose more or less produced, with its under side convex, and a space between the nostrils and the upper lip covered with close adpressed hairs, and without any median groove.

Rhinogale. —Toes 5-5. Claws of fore feet short, compressed, acute. Under surface of tarsus hairy. Founded on a single specimen from East Africa, R. melleri. Crossarchus.— Dentition: i ⅜, c 1 , p ∣ , m ⅜; total 36. Snout elongated. Toes 5-5. Claws on fore feet long and curved. Hallux very short. Under surface of tarsus naked. Tail shorter than the body, tapering. Fur harsh. Species: C. obscurus, the Kusimanse, a small burrowing animal from West Africa, of uniform dark-brown colour; C. fasciatus ; C. zebra; C. gambiamιs. Suricata.— A more distinct genus than any of the above. The dental formula as in the last, but the teeth of the molar series remarkably short in the antero-posterior direction, corresponding with the shortness of the skull generally. Orbits complete behind. Vertebrae: C 7, D l·5, I. 6, S 3, C 20. Though the head is short and broad, the nose is pointed and rather produced and movable. Ears very short. Body shorter and limbs longer than in Herpestes. Toes 4-4, the pollex andhallux being absent. Claws onfore Γeetvery long and narrow, arched, pointed, and subequal. Hind feet with much shorter claws, soles hairy. Tail rather shorter than the body. One species only is known, the Suricate, S. tetradactyla', a small greybrown animal, with dark transverse stripes on the hinder part of the back, from South Africa.

Galidictis, Galidea, and Hemigalidia are names of three slight generic modifications of the Viverrine type, allied to the Herpes- tinae, but placed by Mivart in a distinct subfamily, Galidictinae. They are all inhabitants of Madagascar. The best-known, Galidia elegans, is a lively Squirrel-like little animal with soft fur and a long bushy tail, which climbs and jumps with agility. It is of a chestnut-brown colour, the tail being annulated with darker brown. Galidictis vittata and striata chiefly differ from the Ichneumons in their coloration, being grey with parallel longitudinal stripes of dark brown.

Eupleres is another form, also from Madagascar, which has been placed in a subfamily apart. It differs remarkably from all the other Viverridae in the weak development of the jaws and the small

•size of the teeth, in consequence of which it was, when first discovered, placed inthe order Insectivora. Dentition: i ⅜, c ∣ , p f,

⅜ = 40. Vertebrae: C 7, D 13, I. 7, S 3, C 20. But one species is known, E. goudoti. Family Hyaenidae.

No alisphenoid canal. Dorsal vertebrae 15. Molars ⅛. Limited to the Old World.

Subfamily Protelidae. —Auditory bulla divided into two distinct chambers. Premolar and molar teeth very small and simple in character.

This group contains but a single species, belonging to the genus Proteles, P. cristatus, the Aard-Wolf or Earth-Wolf of the Dutch colonists of the Cape, an animal nearly allied to the Hyaenas, but remarkably modified in its dentition, the molar teeth being very small, placed far apart, and almost rudimentary in character (see fig. 119). The canines are long and rather slender. The dental formula is i ∣, c ⅛, p and m 3 -⅛ 7 -⅛θ; total 30 or 32. Vertebrae:

D15, L5, S 2, C 24. The fore feet with five toes; the pollex, though short, with a distinct claw. The hind feet with four subequal toes. Claws all strong, blunt, subcompressed, and non-retractile. The general external appearance is very like that of a small striped Hyaena, but the muzzle is more pointed and the ears larger. It has a copious mane of long hair, capable of being erected, when the animal is excited, along the middle line of the neck and back. It is a native of South Africa, and is a burrowing nocturnal animal, feeding on decomposing animal substances, larvae, and termites. Observations upon specimens in captivity indicate that it has neither inclination nor power to attack or feed upon living vertebrated animals.

Subfamily Hyaenidae.—Auditory bulla not divided by a septum into two chambers.

Hyaena. — Dentition: ∙i ⅜, c f, p ⅜, m ⅛ = f; total 34. Teeth, especially canines and premolars, very large, strong, and conical. Upper sectorial with a very large, distinctly trilobed blade and a moderately developed inner lobe placed at the anterior extremity of the blade. Molar very small, and placed transversely close to the hinder edge of the last, as in the Felidsβ. Lower sectorial consisting of little more than the bilobed blade. Zygomatic arches of cranium very wide and strong. Sagittal crest high, giving attachment to very powerful biting muscles. Orbits incomplete behind. Vertebrae: C 7, D15, I. 5, S 4, C 19. Limbs rather long, especially the anterior pair, digitigrade, four subequal toes on each, with stout non-retractile claws. Pollex and hallux only represented by rudimentary metacarpal and metatarsal bones. Tail rather short. A large post-anal median glandular pouch, into which the largely developed anal scent glands pour their secretion.

The three existing species of Hyaena (see Hyaena) are divisible into two sections to which some zoologists assign generic rank.

1. Upper molar moderately developed and three-rooted. An inner tubercle and heel more or less developed on the lower molar. Ears large, pointed. Hair long, forming a mane on the back and shoulders. H. striata, the Striped Hyaena, of northern Africa and southern Asia. H. brunnea, of south Africa, in some respects intermediate between this and the next section. 2. Genus Crocuta. Upper molar extremely small, two-or one-rooted, often deciduous. Lower molar without trace of inner tubercle, and with an extremely small heel. Ears moderate, rounded. Hair not elongated to form a mane. H. crocuta or Crocuta maculata, the Spotted Hyaena, from Africa south of the Sahara. In dental characters the first section inclines more to the Viverridae, the second to the Felidae ; or the second may be considered as the more specialized form, as it certainly is in its visceral anatomy, especially in that of the reproductive organs of the female. Extinct Hyaenidae. — Hyaenas abounded in Europe from the Upper Miocene to the Pleistocene epoch, and a series of transitional forms from ancient generalized types merging into Viverridae, as Icti-therium and Hyaenictis (with additional tubercular molars), leading by gradual modifications during successive geological ages to the species now existing, have been traced by Gaudry. The Cave Hyaena {H. spelaea), once so abundant in Britain and other parts of Europe, is scarcely distinguishable specifically from the existing H. crocuta of Africa; and extinct forms found in France, described under the names of H. prisca and H. arvernensis, are probably the ancestors of H. striata. The existing H. brunnea seems to have preserved the characters of H. eximia of the Upper Miocene of Pikermi in Greece with little modification. There is at present no evidence of the existence of this group in America.

Section Cynoidea.

This section contains a single family, Canidae, or Dog-like animals, which appear to hold an intermediate position between the other two sections, retaining also many of the more generalized characters of the ancient members of the order. The structure of the auditory bulla and adjacent parts of the bones of the skull is quite intermediate between that of the Aeluroid and Arctoid forms. In the number and arrangement of the teeth they more nearly approach the primitive heterodont type than any other existing Carnivora. A caecum is always present, sometimes short and simple, but when long it is folded upon itself in a characteristic manner.

The Dogs form a very compact group, composed of numerous species which closely resemble each other in essential characters, though differing considerably externally. The most marked differences are a slight variation in the number of the true molar teeth, which exceed the usual number in the Cape Long-eared Fox (Otocyon), and fall short of it in some other less aberrant forms to which the names of Icticyon and Cyan have been given, and a diminution in the number of toes in the Cape Hunting Dog (Lycaon), which has 4-4, instead of 5-4 as in the remainder of the family. After taking these away, there remain a great number of animals called Dogs, Wolves, Jackals, and Foxes, varying from one another only in the characters of the tail, ears, fur, form of the pupil, and some trifling peculiarities of skull and teeth, upon which some authors have divided them into many genera. These divisions are, however, extremely difficult, if not impossible, to define, bn account of the numerous gradual transitions from one form to the other.

Canis. — Pending further investigation, it will perhaps be safest to retain all the species, with the exceptions of Otocyon and Lycaon mentioned above, in the old genus Canis, the most prominent characters of which are the following. Teeth, usually i ⅜, c ⅛, p ⅜, m f=rr> total 42. The absence of the last upper molar (m 3), alone distinguishes this from the generalized dentition of heterodonts (see p. 353), and this tooth is occasionally present in one species (O'. cancrivorus). In certain Asiatic species (C. primaevus and its allies), which on this account have been separated to form the genus Cyan of Hodgson, the last lower molar (m 3) appears to be constantly absent, and in C. venaticus (genus Icticyon, Lund) not only this but also m 2 is usually not developed. The milk dentition is eft f, de ⅜, dm ⅜ = yj total 28,—the first permanent premolar having no predecessor. The teeth of both permanent and milk or temporary series are figured at p. 353 (fig. 3). The upper sectorial p 4 consists of a stout blade, of which the anterior cusp is almost obsolete, the middle cusp large, conical, and pointed backwards, and the posterior cusp in the form of a compressed ridge; the inner lobe is very small, and placed quite at the fore part of the tooth. The first molar is more than half the antero-posterior length of the sectorial, and considerably wider than it is long; its crown consists of two prominent conical cusps, of which the anterior is the larger, and a low broad inward prolongation, supporting two more or less distinct cusps and a raised inner border. The second molar resembles the first in general form, but is considerably smaller. The lower sectorial m 1 is a very large tooth, with a strong compressed bilobed blade, the hinder lobe being considerably the larger and more pointed, a small but distinct inner tubercle placed at the hinder margin of the posterior lobe of the blade, and a broad, low, tuberculated heel, occupying about one-third of the whole length of the tooth. The second molar is less than half the length of the first, with a pair of cusps placed side by side anteriorly, and a less distinct posterior pair. The third is an extremely small and simple tooth with a subcircular tuberculated crown and single root.

The cranium is more or less elongated, the facial portion tapering forwards and compressed. The jaws elongated. The zygomata moderately strong. The post-orbital processes of the frontal short, leaving the orbit widely open posteriorly. Vertebrae: C 7, D 13, I. 7, S 3, C 17-22. Clavicles present, but very rudimentary. Limbs of moderate proportions, digitigrade. Feet shoYt; five toes on the fore foot, the pollex much shorter than the others, and not reaching to the ground. Four toes on the hind foot, the hallux being represented by a rudiment of the metatarsal. All the toes are provided with exserted non-retractile slightly curved and blunt claws, which, being exposed, become worn at the tips. Tail moderate, or rather long, generally somewhat bushy. The pupil of the eye, when contracted, is in some species round, in others elliptical and vertical.

This extensive genus may be considered as truly cosmopolitan. One or more species are found throughout the American continent from Greenland to Patagonia and the Falkland Isles; and similarly, in the Old World, Europe, Africa, and Asia, with most of the large islands adjacent, and even Australia, have their wild Dogs, though in the last case they probably belong to a feral race, introduced originally by man. They are generally sociable animals, hunting their prey in packs. Many species burrow in the ground; none habitually climb trees. Though mostly carnivorous, feeding chiefly on animals they have chased and killed themselves, many, especially among the smaller species, eat garbage, carrion, insects, and also fruit, berries, and other vegetable substances. The species are very numerous, and, as in most other large genera, very ill-defined, few zoologists agreeing as to which of the many slightly different modifications may be considered as local varieties and which true species. Perhaps the best cranial character by which the different members of the genus can be distinguished is that pointed out by Burmeister, viz., that in the animals generally called Dogs, Wolves, and Jackals the post-orbital process of the frontal bone is regularly smooth and convex above, with its extremity bent downwards, whereas in Foxes the process is hollowed above, with its outer margin (particularly of the anterior border) somewhat raised. This modification coincides in the main with that upon which Professor Huxley has recently based his division of the group into two parallel series, the Thooids or Lupine forms and Alopecoids or Vulpine forms, which he characterizes by the presence of frontal air-sinuses in the former, which not only affects the external form but to a still greater degree the shape of the anterior part of the cranial cavity, and the absence of such sinuses in the latter. The pupil of the eye when contracted is round in most members of the first group, and vertically elliptical in the others, but more observations are required before this character can be absolutely relied upon. The form and length of the tail is often used for the purposes of classification, but its characters do not coincide with those of the cranium, as many of the South American Canidae have the long busby tails of Foxes and the skulls of Wolves. Taking into account various combinations of these and other minor characters, the species may be arranged in the following groups, which some authors have considered as of generic importance.

A. Thooid or Lupine Series.

(1) Canis proper contains the largest members of the genus, the true Wolves of the northern parts of both Old and New Worlds (O'. lupus, &c. ), the Jackals of southern Asia and Africa (O'. aureus, mesomelas, &c.), and the various breeds of the domestic Dog (C. familiaris), the origin of which is still involved in obscurity. Some naturalists believe it to be a distinct species, descended from one that no longer exists in a wild state; others have sought to find its progenitors in some one of the wild or feral races, either of true Hogs, Wolves, or Jackals; while others again believe that it is derived from the mingling of two or more wild species or races. It is probably the earliest animal domesticated by man, and few if any other species have undergone such an extraordinary amount of variation in size, form, and proportion of limbs, ears, and tail, variations which have been perpetuated and increased by careful selective breeding. See Dog. The Dingo or Australian Dog is met with wild, and also as the domestic companion of the aboriginal people. Dogs were also in the possession of the natives of New Zealand and other islands of the Pacific, where no placental mammals exist naturally, on their discovery by Europeans in the last century. (2) Cyon, wild Dogs of the south-east of Asia, distinguished by slight modifications as C. primaevus, C. dukh-enensis, and C. sumatrensis, differ from the above in wanting the small last»lower tubercular molar. (3) Lycalopex is a group formed of certain South-American Canidae, distinguished from Canis proper by their longer tails and Fox-like aspect :— C. cancrivorus, C. lrasili-ensis, C. melampus, C. vetulus, C. fulvicaudus, C. azarae, C. megellani- eus, C. griseus. The last three have been further separated (under the name of Pseudalopex) on account of slight differences in the relative size of the molar teeth, and of their pupil being elliptical when contracted. (4) Nyctereutes (one species, C. procyonides, from Japan and north-east Asia) has no claims to generic distinction but such as are founded upon its long loose fur, short ears, and short bushy tail, which give it some superficial resemblance to a Raccoon. (5) Icticyon, with one small species, C. venaticus, the Bush Dog, from Guiana and Brazil, with close hair, and short legs and tail, has more reason to be regarded as a distinct form, as it is distinguished from all other Dogs by the reduction of its molar teeth to ⅜, and their comparatively small size. In consequence of this, and its general external characters, it was formerly placed among the Mustelidae, but its Canine affinities have now been thoroughly established.

B. Alopecoid or Vulpine Series.

(6) Vulpes, true Foxes. The species or varieties are numerous and widely spread over North America, Eurasia, and Africa :— C. vulpes, the common Fox of Europe; C. niloticus, adustus, and variegatus, Africa; C. flavescens, montanus, iengalensis, japonicus, corsae, Asia; C. fulvus, macrourus, velox, North America. The tail of the above is clothed with soft fur and long hair, uniformly mixed; from them Baird distinguishes, under the name of Urocyon, other species which have a concealed erect mane of stiff hairs along the upper line of the tail. These have also a shorter muzzle and a wide space between the temporal crests; they are C. virginianus and C. litteralis, both from North America. The Arctic Fox (O'. lagopus, genus Leucocyon, Gray) has the tail very full and bushy and the soles of the feet densely furred below. Its colour changes according to season from bluish-grey to pure white. (7) Fennecus. Certain small elegant African Foxes (O'. cerdo, famelicus, and chama), with very large ears and corresponding large auditory bullae, have been separated under the above name.

Lycaon. — This resembles in most of its characters the Dogs of the Lupine series, but the teeth are rather more massive and rounded, the skull shorter and broader, and it has but four toes on each limb, as in Hyaena. The one species, I.. pictus, the Cape Hunting Dog (fig. 120) from south and east Africa, is very distinct externally from all the other Canidae. It is nearly as large as a mastiff, with large, broadly ovate erect ears, and singularly coloured, being not only variable in different individuals, but unsymmetrically marked with large spots of white, yellow, and black. It presents some curious superficial resemblances to Hyaena crocuta, perhaps a case of mimetic analogy. It hunts its prey in large packs.

Otocyon. —Dentition: i ∣ , c ∣ , p ∣ , m 3 ~2p= n °' 12 ; total 46 or 48. The molar teeth are thus in excess of any other known heterodont mammal. They have the same general characters as in Canis, with very pointed cusps. The lower sectorial shows little of its typical characters, having five cusps on the surface; these can, however, be identified as the inner tubercle, the two greatly reduced and obliquely placed lobes of the blade, and two cusps on the heel. The skull generally resembles that of the smaller Foxes, particularly the Fennecs. The auditory bullae are very large. The hinder edge of the mandible has a very peculiar form, owing to the great development of an expanded, compressed, and somewhat inverted subangular process. Vertebrae: C 7, D 13, I. 7, S 3, C 22. Ears very large. Limbs rather long. Toes 5-4. One species, 0. megalotis, from South Africa, rather smaller than a common Fox.

Professor Huxley looks upon this as the least differentiated or most primitive existing form of Canis, regarding the presence of the four molar teeth as a survival of a condition of the dentition exhibited by the common ancestors of the existing Canidae and the existing carnivorous Marsupials. There is, however, at present no palaeontological proof of this, as none of the numerous fossil forms of Canidae yet discovered have more than the normal number of molars. One of the best known of these is Amphicyon, from the Miocene strata of Europe and America, formerly supposed to have affinities with the Bears, having five toes on each foot, and being possibly plantigrade, but, as the structure of the skull and teeth clearly show, only a generalized Dog, in which the true molars are fully developed. Another genus, Cynodictis, of which many modifications have been described by Filhol from the south of France, approaches the Viverridae, and may be a common ancestor of the Cynoid and Aeluroid Carnivora.

Section Arctoidea.

The section Arctoidea includes a considerable number of forms which agree in the essential characteristics of the structures of the base of the cranium and reproductive organs, and in the absence of a caecum to the intestinal canal. They have no Cowper’s glands, and have a rudimentary prostate and a large cylindrical penial bone. All the members of this group have five completely developed toes on each foot.

Family Mustelidae.

True molars ⅛ (or } in Mellivora). No alisphenoid canal. A large group widely diffused, especially in the northern temperate legions of the earth. The different genera are very difficult to arrange in any natural order. They are rather artificially divided, chiefly according to the characters of their feet and claws, into the Otter-like (Lutnne), Badger-like (Meline), and Weasel-like (Musteline) forms.

Subfamily Lutrinae.—Feet short, rounded (except the hind feet of Enhydra). Toes webbed. Claws small, curved, blunt. Head broad and much depressed. Upper posterior molars large and quadrate. Kidneys conglomerate. Habits aquatic.

Lutra.— Dentition: i ∣ , c ⅜, p ⅜, m ⅜; total 36. Upper sectorial with a trenchant tricusped blade, and a very large inner lobe, hollowed on the free surface, with a raised sharp edge, and extending along two-thirds or more of the length of the blade. True molar large, with a quadricuspidate crown, broader than long. Skull broad and depressed, contracted immediately behind the orbits. Facial portion very short; brain case large. Vertebrae: C 7, D 14-15, I. 6-5, S3, C 20-26. Body very long. Ears short and rounded. Limbs short. Feet completely webbed, with well developed claws on all the toes. Tail long, thick at the base and tapering, rather depressed. Fur short and close.

The Otters are all more or less aquatic, living on the margins of rivers, lakes, and in some cases the sea, are expert divers and swimmers, and feed chiefly on fish. They have a very extensive geographical range, and so much resemble each other in outward appearance, especially in the nearly uniform brown colouring, that the species are by no means well-defined. See Otter. I.. sandbachii, a very large species from Demerara and Surinam, with a prominent ridge along each lateral margin of the tail, constitutes the genus Pteronura of Gray.

Aonyx.— Feet only slightly webbed; claws exceedingly small or altogether wanting on some of the toes. First upper premolar very small, sometimes wanting. True molars very broad and massive, presenting an approach to the form of the next genus. A. inunguis, South Africa; A. leptonyx, Java, Sumatra.

Erihydriodon.—E. sivalensis is a large extinct Otter-like animal described by Dr Falconer from the Pliocene strata of the Sub-himalayan mountains.

Enhydra.— Dentition: i ∣, c ⅜, p ∣ , m ⅜; total 32. Differs from all other kuown Carnivora in having but two incisors on each side of the lower jaw, the one corresponding to the first (very small in the true Otters) being constantly absent. Though the molar teeth generally resemble those of Lutra in their proportions, they differ very much in the exceeding roundness and massiveness of their crowns and bluritness of their cusps. Feet webbed. Fore feet short, with five subequal toes, with short compressed claws. Hind feet very large, depressed, and fin-like. The phalanges flattened as in the Seals. The fifth toe the longest and stoutest, the rest gradually diminishing in size to the first, all with moderate claws. Tail moderate, cylindrical.

One species, E. lutris, the Sea-Otter. It is larger than any of the true Otters, and is found only on the coasts and islands of the North Pacific, where it was formerly very abundant, but is gradually becoming more and more rare, on account of the numbers killed annually for their valuable fur. It is said to live on molluscs and crabs as well as fish, and the massive mill-like structure of the grinding teeth, so unlike that of all the kuown purely piscivorous mammals, would seem to indicate some such diet.

Subfamily Melinae.—Feet elongated. Toes straight. Claws non-retractile, slightly curved, subcompressed, blunt; those of the fore foot especially large. Upper posterior molar variable. Kidneys simple. Habits mostly terrestrial and fossorial.

Mephitis.— Dentition: i ⅜, c ⅜, p , m ⅜; total 32-34. Upper molar larger than the sectorial, subquadrate, rather broader than long. Lower sectorial with heel less than half the length of the whole tooth. Bony palate terminating posteriorly opposite the hinder border of the last molar tooth. Facial portion of skull short and somewhat truncated in front. Vertebrae: C7, D 16, L6, S2, C21. Headsmall. Body elongated. Limbs moderate, subplantigrade. Ears short and rounded. Tail long, abundantly clothed with very long fine hair. Anal glands largely developed; their secretion, which can be discharged at the will of the animal, has an intolerably offensive odour, which circumstance has rendered the Skunks, as they are commonly called, proverbial. They are strictly nocturnal animals, terrestrial and burrowing, feeding chiefly on small mammals, birds, reptiles, insects, worms, roots, and berries. All the known species have a prevalent black colour, varied by white stripes or spots on the upper part. They generally carry the body much arched, and the tail erect, the long loose hair of which waves like a plume over the back. There are many species, all inhabitants of the American continent, over which they have an extensive range. See Skunk. The South-American species, which have only two upper premolars, and differ in some other characters, have been generically separated under the name of Conepatus. . Arctonyx.— Dentition: i ∣ , c j-, p ∣ , m ⅜; total 38. Incisor line curved, the outer teeth being placed posteriorly to the others. Lower incisors proclivous. First premolars often rudimentary or absent. Upper molar much larger than the sectorial, longer in the antero-posterior direction than broad. Lower sectorial with a very large, low, tuberculated heel. Cranium elongated and depressed; face long, narrow, and concave above. Bony palate extending as far backwards as the level of the glenoid fossa. Palatal bones dilated. Suborbital foramina very large. Vertebrae: C 7, D16, I. 4, S 4, C 20. Snout long, naked, mobile, and truncated, with large terminal nostrils, much like those of a Pig. Eyes small. Ears very small and rounded. Body compressed, rather than depressed. Limbs of moderate length and digitigrade in walking. Tail moderate, tapering. A full soft under fur, with longer, bristly hairs interspersed.. The best-known species is A. collaris, the Sand-Bear or Bhalιi-soor (i.e., Bear-Pig) of the natives, found in the mountains of the north-east of Hindustan and Assam. It is rather larger than the English Badger, higher in its legs, and very Pig-like in general aspect, of a light grey colour, with flesh-coloured snout and feet; nocturnal and omnivorous. Other species or local varieties have been described by A. Milne-Edwards from North China and Tibet.

Mydaus.— Dentition as the last, but the cusps of the teeth more acutely pointed. Cranium elongated, face narrow and produced. Suborbital foramen small, and the palate, as in all the succeeding genera of this group, produced backwards about midway between the last molar tooth and the glenoid fossae. Vertebrae: C 7, D14-15, I. 6-5, S 3, C12. Head pointed in front; snout produced, mobile, obliquely truncated, the nostrils being inferior. Limbs rather short and stout. Tail extremely short, but clothed with rather long bushy hair. Anal glands largely developed, and emitting an odour like that of the American Skunks (Mephitis'). One species, Μ. meliceps, the Teledu, a small burrowing animal, found in the mountains of Java, at an elevation of 7000 or more feet above the sea-level.

Meles. — Dentition: i ⅞, c ∣ , p ∣ , m ⅜; total 38. The first premolar in both jaws extremely minute and often deciduous. Upper molar very much larger than the sectorial, subquadrate, as broad as long. Lower sectorial with a broad, low, tuberculated heel, more than half the length of the whole tooth. The postglenoid processes of the skull are so strongly developed, and the glenoid fossa is so deep, that the condyle of the lower jaw is firmly held, in its place even after all the surrounding soft parts are removed. Vertebrae: C 7, D 15, I. 5, S 3, C18. Muzzle pointed. Ears very short. Body stout, broad. Limbs short, strong, subplantigrade. Tail short. The best-known species is the common Badger (M. taxus) of Europe and northern Asia, still found in many parts of England, where it lives in woods, is nocturnal, burrowing, and very omnivorous, feeding on mice, reptiles, insects, fruit, acorns, and roots. Other nearly allied species, Μ. leucurus and Μ. chinensis, are found in continental Asia, and Μ. anakuma in Japan.

Taxidea.— Dental formula as in Meles, except that the rudimentary anterior premolars appear to be always wanting in the upper jaw. The upper sectorial much larger in proportion to the other teeth. Upper molar about the same size as the sectorial, triangular, with the apex turned backwards. Heel of lower sectorial less than half the length of the tooth. Skull very wide in the occipital region; the lambdoidal crest very greatly developed, and the sagittal but slightly, contrary to what obtains in Meles. Vertebra: C 7, D 15, I. 5, S 3, C (?). Body very stoutly built and depressed. Tail short. The animals of this genus are peculiar to North America, where they represent the Badgers of the Old World, resembling them much in appearance and habits. T. americana is the common American Badger of the United States. T. berlan-dieri, the Mexican Badger, is perhaps only a local variety.

Melliυora.— Dentition: i ⅞, c ⅛, p ⅜, m ⅜; total 32. Upper sectorial large, with its inner cusp quite at the anterior end of the blade, as in the following genera; molar much smaller and transversely extended, having a very small outer and a larger rounded inner lobe. Heel of lower sectorial very small, scarcely one-fourth of the whole length of the tooth, and with but one cusp. Tubercular molar absent. Vertebra: C 7, D 14, I. 4, S 4, C 15. Body stout, depressed. Limbs short, strong. Head depressed, nose rather pointed. External ears rudimentary. Tail short. The animals of this genus are commonly called Ratels. M. indica, from India, and Μ. ratel and Μ. leuconota from South and West Africa, have nearly the same general appearance and size, being rather larger than a common Badger. Their coloration is peculiar, all the upper surface of the body, head, and tail being ash-grey, while the lower parts, separated by a distinct longitudinal boundary line, are black. They live chiefly on the ground, into which they burrow, but can also climb trees. They feed on small mammals, birds, reptiles, and insects, and are said to be very partial to honey.

Helictis.— Dentition: i ∣, c ∣, p ∣ , m ⅜; total 38. Upper sectorial with a large bicusped inner lobe. Molar smaller, wider transversely than in the antero-posterior direction. Lower sectorial with heel about one-third the length of the tooth. Skull elongated, rather narrow and depressed. Facial portion especially narrow. Infraorbital foramen very large. Head rather small and produced in front, with an elongated, obliquely truncated, naked snout. Ears small. Body elongated. Limbs short. Tail short or moderate, bushy. Several species are described (H. orientalis, moschata, nipalensis, subaurantiaca), all from eastern Asia, small animals compared with the other members of the subfamily, climbing trees with agility and living much on fruit and berries as well as on small mammals and birds.

Ictonyx.— Dentition: i ⅜, c f, p ⅜, m J; total 34. In general characters the teeth much resemble those of the Polecats (Mustela), being more delicately cut and sharply cusped than in most of the foregoing. Upper molar smaller than the sectorial, narrow from before backwards. Lower sectorial with a small narrow heel and distinct inner tubercle. General form of body musteline. Limbs short. Fore feet large and broad, with five stout, nearly straight, blunt, and non-retractile claws, of which the first and fifth are considerably shorter than the others. Tail moderate, with longer hairs towards the end, giving it a bushy appearance. Hair generally long and loose. The best-known species of this genus, I. zorilla, the Cape Polecat, was placed by Cuvier in the genus Mustela, by Lichtenstein in Mephitis, and in many characters it forms a transition between these genera. It is about the size of an English Polecat, but conspicuous by its coloration, having broad, longitudinal bands of dark brown, alternating with white. Its odour is said to be as offensive as that of the American Skunks. From the Cape of Good Hope it ranges as far north as Senegal. Another species, I. frenata, from Sennaar, has been described.

Subfamily Mustelinae.—Toes short, partially webbed; claws short, compressed, acute, curved, often semiretractile. Upper posterior-molar of moderate size, wide transversely. Kidneys simple. Terrestrial and arboreal in habits.

Galictis.— Dentition: i ⅜, c ⅛, p ⅞, m ⅜; total 34. Molars small but stout; upper sectorial with the inner lobe near the middle of the inner border of the tooth. Lower sectorial with heel small, and inner tubercle small or absent. Body long. Limbs short; claws non-retractile. Palms and soles naked. Head broad and depressed. Tail of moderate length. The best-known species, G. vittata, the Grison (genus Grisonia, Gray), and G. barbara, the Tayra (genus Galera, Gray), are both South-American; G. alia- mandi is an intermediate form.

Mustela. — Dentition: i f, c ⅜, p ⅜, m ; total 38. Upper sectorial with inner lobe close to the anterior edge of the tooth. Molar nearly as large as sectorial. Lower sectorial with small inner tubercle. Vertebra: C 7, D 14, I. 6, S 3, C 18-23. Body long and slender. Limbs short, digitigrade. Feet rounded; toes short, with compressed, acute, semiretractile claws. Tail moderate or long, more or less bushy. One species is British, M. martes, the Pine Marten; the remainder inhabit the northern regions of Europe, Asia, and America. Many of the species, as the Sable (Μ. zibel∙ Una), yield fur of great value. See Marten. Putorius.— The dentition differs from that of Mustela chiefly in the absence of the anterior premolars of both jaws. The teeth are more sharply cusped, and the lower sectorial wants the inner tubercle. External characters generally similar to those of the Martens, but the body is longer and more slender, and the limbs even shorter. They are all small animals, of very active, bloodthirsty and courageous disposition, living chiefly on birds and small mammals, and are rather terrestrial than arboreal, dwelling among rocks, stones, and outbuildings. Some of the species, as the Stoat or Ermine (P. ermineus), inhabiting cold climates, undergo a seasonal change of colour, being brown in summer and white in winter, though the change does not affect the whole of the fur, the end of the tail remaining black in all seasons. This is a large genus, having a very extensive geographical range throughout the Old and New Worlds, and includes the animals commonly known as Weasels, Polecats, Ferrets, and Minks.

Gulo.— Dentition: i f, c ⅛, p ∣ , m ⅜; total 38. Crowns of the teeth very stout. Upper molar very much smaller than the sectorial. Lower sectorial large, with very small heel and no inner tubercle. The dentition, though really but a modification of that of the Weasels, presents a great general resemblance to that of Hyaena. Vertebra: C 7, D 15, I. 5, S 3, C 15. Body and limbs stoutly made. Feet large and powerful, subplantigrade, with large, compressed, much curved, and sharp-pointed claws. Soles of the feet (except the pads of the toes) covered with thick bristly hairs. Ears very small, nearly concealed by the fur. Eyes small. Tail short, thick, and bushy. Fur full, long, and rather coarse. The one species, the Wolverene or Glutton, G. luscus, an inhabitant of the forest regions of northern Europe, Asia, and America, much resembles a small Bear in appearance. It is a very powerful animal for its size, climbs trees, and lives on squirrels, hares, beavers, reindeer, and is said to attack even horses and cows.

Family Procyonidae.

True molars ⅜, obtusely tuberculated. No alisphenoid canal. Habitat exclusively American.

Procyon,— Dentition: i ⅜, c -}, p ∣ , m ⅜; total 40. The molar teeth broad and tuberculated. The upper sectorial with three cusps along the outer margin, and a very broad bicusped inner lobe, giving an almost quadrate form to the crown. First molar with a large tuberculated crown, rather broader than long. Second considerably smaller, with transversely oblong crown. Lower sectorial with an extremely small and ill-defined blade, placed transversely in front, and a large inner tubercle and heel. Second molar as long as the first, but narrower behind, with five obtuse cusps. Vertebrae: C 7, D 14, I. 6, S 3, C 16-20. Body stout. Head broad behind, but with a pointed muzzle. Limbs plantigrade, but in walking the entire sole is not applied to the ground as it is when the animal is standing. Toes, especially of the fore foot, very free, and capable of being spread wide apart. Claws compressed, curved, pointed, and non-retractile. Tail moderately long, cylindrical, thickly covered with hair, annula ted, non-prehensile. Fur long, thick, and soft. The well-known Raccoon (Procyon lotor) of North America is the type of this genus. It is replaced in South America by P. cancrivorus. Bassaris. — A form closely allied to Procyon, but of more slender and elegant proportions, with sharper nose, longer tail, and more digitigrade feet, and with teeth otherwise like, but smaller, and more sharply denticulated. It was formerly, but erroneously, placed among the Viverridae. Two species :— B. astuta, from the southern parts of the United States and Mexico, and B. sumi-chrasti, from Central America.

Bassaricyon.— This name has recently (1876) been given to a distinct modification of the Procyonine type of which at present only two examples are known, one from Costa Rica and the other from Ecuador, which, appearing to be different species, have been named B. gabbi and B. alleni. They much resemble the Kinkajou (Cercoleptes) in external appearance, but the skull and teeth are more like those of Procyon and Nasua. Nasua.— Dentition as in Procyon, but the upper canines are larger and more strongly compressed, and the molars smaller. The facial portion of the skull is more elongated and narrow. Vertebrae: C 7, D 14, I. 6, S 3, C 22-23. Body elongated and rather compressed. Nose prolonged into a somewhat upturned, obliquely truncated, mobile snout. Tail long, non-prehensile, tapering, annulated. These animals, commonly called Coatis or Coati-Mundis, live in small troops of eight to twenty, are chiefly arboreal, and feed on fruits, young birds, eggs, insects, &c. Recent researches have reduced the number of supposed species to two, N. narica of Mexico and Central America, and Λ r . rufa of South America from Surinam to Paraguay.

Cercolcptes.— Dentition: i ⅞, c f, p ⅜, m ⅜ = 36. Molars with low flat crowns, very obscurely tuberculated. Skull short and rounded, with flat upper surface. Vertebrae: C 7, D 14, I. 6, S 3, C 26-28. Clavicles present, but in a very rudimentary condition. Head broad and round. Ears short. Body long and musteline. Limbs short. Tail long, tapering, and prehensile. Fur short and soft. Tongue long and very extensile. But one species of this somewhat aberrant genus is known, C. caudiυolmιlus, the Kinkajou, found in the forests of the warmer parts of South and Central America. It is about the size of a Cat, of a uniform pale, yellowish-brown colour, nocturnal and arboreal in its habits, feeding on fruit, honey, eggs, and small birds and mammals, and is of a tolerably gentle disposition and easily tamed.

Family Ailuridae.

Formed for the reception of one genus, resembling the Procyonidae in the number of true molar teeth, but differing in some cranial characters, especially the presence of an alisphenoid canal, and in its Asiatic habitat.

Ailurus.— Dentition: i ⅜, c⅛, p ∣ , m f; total 38. First lower premolar very minute and deciduous. Molars remarkable for their great transverse breadth, and the numerous cusps of their crowns. Vertebrae: C 7, D 14, I. 6, S 3, C 18. Skull high and compressed. Facial portion short. Ascending ramus of mandible extremely high. Head round. Face short and broad. Ears large, erect, pointed. Limbs stout, plantigrade, with large blunt non-retractile claws. Tail nearly as long as body, cylindrical, clothed with long hairs. Fur long and thick. One species, A. fulgens, the Panda, rather larger than a Cat, found in the south-east Himalayas, at heights of from 7000 to 12,000 feet above the sea, among rocks and trees, and chiefly feeding on fruits and other vegetable substances. Its fur is of a remarkably rich reddish-brown colour, darker below.

Family Ursidae.

True molars ⅜, with broad, flat, tuberculated crowns. The three anterior premolars of both jaws rudimentary and often deciduous. Fourth upper premolar (sectorial) with no third or inner root. No alisphenoid canal (except in Ailuropus). Kidneys conglomerate. Geographical distribution extensive.

Ail·uropus.— An interesting annectant form connecting the true Bears with Ailurus and with several extinct genera. Dentition: »' ⅜> c τ, P ⅜> m I i total 40. Premolars increasing in size from first to last, and two-rooted except the first. First upper molar with quadrate crown, broader than long. Second larger than the first. Cranium with zygomatic arches and sagittal crest immensely developed, and ascending ramus of mandible very high, giving greater spaces for attachments of temporal muscle than in any other existing member of the order. Facial portion short. Bony palate not extending behind the last molar tooth. An alisphenoid canal. Feet bear-like, but soles more hairy, and perhaps less completely plantigrade. Fur long and thick. Tail very short. One extremely rare species, A. melanoleucus (fig. 121), discovered by Père David in 1869, in the most inaccessible mountains of eastern Tibet. Said to feed principally on roots, bamboos, and other vegetables. It is of the size of a small Brown Bear, of a white colour, with ears, spots round the eyes, shoulders, and limbs black.

Ursus. — Dentition: i ⅜, c ⅛, p ⅜, m § = 42. The three anterior premolars above and below one-rooted, rudimentary, and frequently wanting. Usually thé first (placed close to the canine) is present, and after a considerable interval the third, which is situated close to the other teeth of the molar series. The second is very rarely present in the adult state. The fourth (upper sectorial) differs essentially from the corresponding tooth of other Carnivores in wanting the inner lobe supported by a distinct root. Its sectorial characters are very slightly marked. The crowns of both the true molars are longer than broad, with flattened, tuberculated, grinding surfaces. The second has a large backward prolongation or heel. The lower sectorial has a small and indistinct blade and greatly developed tubercular heel. The second molar is of about the same length, but with a broader and more flattened tubercular crown. The third is smaller. The milk teeth are comparatively small, and shed at an early age. Skull more or less elongated. Orbits small and incomplete behind. Palate prolonged considerably behind the last molar tooth. Vertebrae: C 7, D 14, I. 6, S 5, C 8-10. Body heavy. Feet broad, completely plantigrade. The five toes on each foot all well-developed, and armed with long compressed and moderately curved, non-retractile claws. Palms and soles naked. Tail very short. Ears moderate, erect, rounded, hairy. Fur generally long, soft, and shaggy.

The Bears are all animals of considerable bulk, and include among them the largest members of the order. Though the species are not numerous, they are widely spread over the earth’s surface (but absent from the Ethiopian and Australian regions, and only represented by one species in the Neotropical region), and differ much among themselves in their food and manner of life. They are mostly omnivorous or vegetable feeders, and even the Polar Bear, usually purely carnivorous or piscivorous, devours grass with avidity in summer. The various species may be grouped in the following sections. (1) Tlιalassarctos. Head comparatively small, molar teeth small and narrow. Soles more covered with hair than in the other sections. U. maritimus, the Polar or White Bear of the Arctic regions. (2) Ursus proper. U. arctos, the common Brown Bear of Europe and Asia, a very variable species, to which U. syriacus and isdbellinus, if distinct, are nearly related; U. horribilis, the Grizzly Bear, an American representative form; U tibetanus, japonicus, and amerimnus, the Black Bears of the Himalayas, Japan, and North America; U. ornatus, the Spectacled Bear of the Peruvian Andes. (3) Helarctos. Head short and broad. Molar teeth comparatively broad (but the length still exceeding the breadth). Tongue very long and extensile. 1 ur short and smooth. U. malayanus, the Malay Bear or Sun Bear. See Bear. > Melursus. This differs from the true Bears in the first upper incisor being absent or shed at a very early age, in the very small size of the other teeth, in the very large extensile lips, and. in other minor characters. The one species, Μ. ldbiatus, the well-known Sloth Bear of India, feeds chiefly on black ants, termites, beetles, fruit, honey, &c.

The great Cave Bear, the remains of which are found, so abundantly in caves of Pleistocene age in Europe, was a true Ursus, and as much or more specialized as any existing species, as it had lost its three anterior premolars in the adult state, but in Ursus arvernensis and older species from the Pliocene they were all retained. Still more generalized forms of Bears, presenting various degrees of transition towards a common Carnivorous type, are represented by the genera Arctotherium from South America and Hyaenarctos of Miocene strata of Europe and Asia, and others which are not far removed (at least in dental characters) from such primitive Dog-like types as Amphicyon. Extinct Carnivora of Doubtful Position.

The discovery of fossil remains in Eocene and early Miocene formations both in Europe and North America, shows that numerous species of terrestrial carnivorous animals existed upon the earth during those periods, which cannot be referred to either of the sections into which the order has now become broken up. By some zoologists these have been supposed to be Marsupials, or at least to show transitional characters between the Didelphous and Monodelphous subclasses. By others they are looked upon as belonging altogether to the latter group, and as the common ancestors of existing Carnivores and Insectivores, or perhaps rather as descendants or relatives of such common ancestors, retaining more of the generalized characters than any of the existing species. They shade off almost insensibly into numerous other forms less distinctly carnivorous, to the whole of which, including the modern Insectivora, Cope (to whom we are indebted for our principal knowledge of the American extinct species) gives the name of Bunotheria, those more specially related to the existing Carnivora forming the suborder Creodonta, which is divided into the five families, Arctocyonidae, Miacidae, Oxyaenidae, Amblyctonidae, and Meronychidae. These are cases, however, in which the application of the principles of classification adopted in the case of existing species, of which the entire structure is known, and which have become divided into isolated groups by the extinction of intermediate forms, is really impossible. If the generally accepted view of evolution is true, and the extreme modifications pass insensibly into each other by minute gradations (a view the palaeontological proof of which becomes strengthened by every fresh discovery), there must be many of these extinct forms which cannot be assigned to definitely characterized groups. There are, however, some which stand out prominently from the others as formed on distinct types, having no exact representatives at present living on the earth. Of these the best-known is that named Hyaenodon, of which, with the nearly allied Pterodon, many species have been found both in Europe and America. They had the full number of forty-four teeth, grouped in the usual manner, and the incisors, canines, and premolars were formed upon the ordinary Carnivorous type as now seen in the Canidεe, the fourth premolar above and the first true molar below being formed upon the “sectorial” plan, but the teeth behind these, instead of being tuberculated as in all existing Carnivora, repeated the characters of the sectorial, and also increased in size, especially in the lower jaw, from before backwards. They thus present some resemblance to the teeth of such carnivorous Marsupials as the Dasyuridae ; but, as the researches of Filhol have demonstrated, their milk dentition follows precisely the rule of existing placental heterodont mammals, and not that characteristic of the Marsupials. They show, moreover, none of the essential cranial modifications which distinguish true Marsupials. The curious American genus Oxana seems to have been a specialized form of this type, and the European Proviverra or Cynohyaenodon of Filhol) forms a complete transition between it and the Viverridae. In Arctocyon primaevus, the oldest known Tertiary mammal, from the lowest Eocene beds of La Fère, department of Aisne, France, on the other hand, all the molars were tuberculated, and have been compared with those of the Procyonida and also Gymnura, among the Insectivora. The small size of the brain of these early forms is not, as has been supposed, a special Marsupial character, but is common to the primitive forms of all groups of vertebrates. Mesonyx, from the Eocene of North America, seems to have been a very generalized form, with flat blunt claws, and long and slender tail. Cope makes the interesting suggestion that this may have been in the ancestral line of the Pinnipeds, but his statement that the scaphoid and lunar bones of the carpus were distinct offers a decided difficulty to the acceptance of this view.

Suborder PINNIPEDIA.

These differ from the' rest of the Carnivora mainly in the structure of their limbs, which are modified for aquatic progression,—the two proximal segments being very short and partially enveloped in the general integument of the body, while the third segment, especially in the hinder extremities, is elongated, expanded, and webbed. There are always five well-developed digits on each limb. In the hind limb the two marginal digits (first and fifth) are stouter and generally larger than the others. The teeth also differ from those of the more typical Carnivora. The incisors are always fewer than ⅜. The molar series consists generally of four premolars and one molar of very uniform characters, with never more than two roots, and with conical, more or less compressed, pointed crowns, which may have accessory cusps, placed before or behind the principal one, but are never broad and tuberculated. The milk teeth are very small and simple, and are shed or absorbed at a very early age, usually either before or within a few days after birth. The brain is relatively large, the cerebral hemispheres broad in proportion to their length, and with numerous and complex convolutions. There is a very short caecum. The kidneys are divided into numerous distinct lobules. There are no Cowper’s glands. Mammae two or four, abdominal. No clavicles. Tail always very short. Eyes very large and exposed, with flat cornea. The nostrils close by the elasticity of their walls, and are opened at will by muscular action.

The animals of this group are all aquatic in their mode of life, spending the greater part of their time in the water, swimming and diving with great facility, feeding mainly on fish, crustaceans, and other marine animals, and progressing on land with difficulty. They always come on shore, however, for the purpose of bringing forth their young. They are generally marine, but they occasionally ascend large rivers, and some inhabit inland seas and lakes, as the Caspian and Baikal. Though not numerous in species, they are widely distributed over the world, but occur most abundantly on the coasts of lands situated in cold and temperate zones. The suborder is divisible into three well-marked families :—the Otariidae or Sea Bears, which form a transition from the Fissiped Carnivora to the Seals; the Trichechidae, containing the Walrus; and the Phocidx or typical Seals.

Family Otariidae.

When on land the hind feet are turned forwards under the body, and aid in supporting and moving the trunk as in ordinary quadrupeds. A small external ear. Testes suspended in a distinct external scrotum. Skull with post-orbital processes and alisphenoid canal. Palms and soles of feet naked.

Otaria.— Dentition: i ∣ , c ⅛, p ∣ , m 1 ~; total 34 or 36. First and second upper incisors small, with the summits of the crowns divided by a deep transverse groove into an anterior and a posterior cusp of nearly equal height; the third large and canine-like. Canines large, conical, pointed, recurved. Molars and premolars, usually f, of which the second, third, and fourth are preceded by milk teeth shed a few days after birth; sometimes (as in fig. 123) a sixth upper molar (occasionally developed on one side and not the other); all with similar characters, generally uniradicular; crown moderate, compressed, pointed, with a single principal cusp, and sometimes a cingulum, and more or less developed anterior and posterior accessory cusps. Vertebrae: C 7, D 15, I. 5, S 4, C

9-10. Head rounded. Eyes large. Pinna of ear small, narrow, and pointed. Neck long. Skin of all the feet extended far beyond the nails and ends of the digits, with a deeply-lobed margin. The nails small and often quite rudimentary, especially those of the first and fifth toes of both feet; the best-developed and most constant are the three middle claws of the hind foot, which are elongated, compressed, and curved.

The Otariae, or Eared Seals, commonly called Sea Bears or Sea Lions, are widely distributed, especially in the temperate regions of both hemispheres, though absent from the coasts of the North Atlantic. As might be inferred from their power of walking on all fours, they spend more of their time on shore, and range inland to greater distances, than the true Seals, especially at the breeding time, though they are obliged always to return to the water to seek their food. They are gregarious and polygamous, and the males are usually much larger than the females, a circumstance which has given rise to some of the confusion existing in the specific determination of the various members of the genus. Some of the species possess, in addition to the stiff, close, hairy covering common to all the group, an exceedingly fine, dense, woolly under fur. The skins of these, when dressed and deprived of the longer harsh outer hairs, constitute the ‘ ‘ sealskin” of commerce, so much valued for wearing apparel, which is not the product of any of the true Seals. The best-known species are 0. stelleri, the Northern Sea Lion, the largest of the genus, from the North Pacific, about 10 feet in length; 0. jubata, the Southern Sea Lion, from the Falkland Islands and Patagonia; 0. californiana, from California, frequently exhibited alive in menageries in Europe; 0. ursina, the common Sea Bear or Fur Seal of the North Pacific, the skins of which are imported in immense numbers from the Prybiloff Islands; 0. pusilla, from the Cape of Good Hope ; 0. forsteri and others, from the coasts of Australia and various islands scattered over the southern hemisphere. These have been grouped by some zoologists into many genera, founded upon very trivial modifications of teeth and skull.

Family Trichf.chidae.

In many characters the single genus comprising this family is intermediate between the Otariidae and Phocidae, but it has a completely aberrant dentition. It has no external ears, as in the Phocidae ; but when on land the hind feet are turned forwards and used in progression, though less completely than in the Otariidae. The upper canines are developed into immense tusks, which descend a long distance below the lower jaw. All the other teeth, including the lower canines, are much alike, small, simple and one-rooted, the molars with flat crowns. The skull is without postorbital process, but has an alisphenoid canal.

Trichechus, Linn.; Odobaenus, Brisson (which some modern zoologists have revived).—Dentition of young: i f, c ⅛, p and m ⅜. Many of these teeth are, however, lost early or remain through life in a rudimentary state, concealed by the gums. The teeth which are usually developed functionally are i ⅜, c ⅛, p ⅜, m ⅜; total 18. Vertebrae: C 7, D 14, I. 6, S 4, C 9. Head round. Eyes rather small. Muzzle short and broad, with on each side a group of long, very stiff, bristly whiskers. The remainder of the hair covering very short and adpressed. Tail very rudimentary. Fore feet with subequal toes, with five minute flattened nails. Hind feet with subequal toes, the fifth slightly the largest, with cutaneous lobes projecting beyond the ends as in Otaria ; first and fifth with minute flattened nails; second, third, and fourth with large, elongated, subcompressed pointed nails.

TheWalrus or Morse (7 ’. rosmarus) is found throughout the circumpolar regions, those of the North Atlantic and North Pacific being considered by some zoologists as distinct species, by others as local varieties. It is gregarious, but, owing to the destruction by the sealers for the sake of its tusks, oil, and hide, it is far less abundant than formerly. The use of the great tusks (which are developed in both sexes, though in the female they are more slender than in the male) appears to be for scraping and digging among the sand and shingle for the molluscs and crustaceans which form its principal sustenance; they are also formidable weapons of defence.

Family Phocidae.

The true Seals are the most completely adapted for aquatic life of all the Pinnipeds. When on land the hind limbs are extended behind them and take no part in progression, which is effected by a series of jumping movements produced by the muscles of the trunk, in some species aided by the fore limbs only. The palms and soles of the feet are hairy. There is no pinna to the ear, and no scrotum, the testes being abdominal. The upper incisors have simple, pointed crowns, and vary in number in the different groups. All have well developed canines and ⅞ teeth of the molar series. In those species of which the milk dentition is known, there are three milk molars, which precede the second, third, and fourth permanent molars; the dentition is therefore p ⅜, m ⅜, the first premolar having as usual no milk predecessor. The skull has no post-orbital process and no alisphenoid canal. The fur is stiff and adpressed, without woolly under fur.

Subfamily Phocinøe.—Incisors ⅜. All feet with five well-developed claws. The toes on the hind feet subequal, the first and fifth not greatly exceeding the others in length, and with the interdigital membrane not extending beyond the toes.

Halichoerus.— Dentition: i ⅜, c ⅛, p ⅜, total 34. Molars with large, simple, conical, recurved, slightly compressed crowns, with sharp anterior and posterior edges, but without accessory cusps, except sometinfes the two hinder ones of the lower jaw. With the exception of the last one or two in the upper jaw and the last in the lower jaw they are all uniradicular. Vertebrae: C 7, D15, L5, S4, C14.

One species, H. grypus, the Grey Seal of the coasts of Scandinavia and the British Isles.

Phoca. — Dental formula as the last. Teeth smaller and more pointed. Molars with two roots (except the first in each jaw). Crowns with accessory cusps. Vertebrae: C7, D 14-15, I. 5, 8 4, C11-14. Head round and short. Fore feet short, with five very strong, subcompressed, slightly curved, rather sharp claws, subequal in length. On the hind feet the claws much narrower and less curved. The species of this genus are widely distributed throughout the northern hemisphere, and include P. barbata, the Bearded Seal; P. groenlandica, the Greenland Seal; P. vitulina, the Common Seal; and P. hispida, the Ringed Seal of the North Atlantic; P. caspica, from the Caspian and Aral Seas; andP. siberica, from Lake Baikal. See Seal.

Subfamily Stenorhynchinae. —Incisors ∣. Molars two-rooted, except the first. On the hind feet the first and fifth toes greatly exceeding the others in length, with nails rudimentary or absent.

Monachus. — Dentition: i ∣ , c ⅜, p ∣ , m f; total 32. Crowns of molars strong, conical, compressed, hollowed on the inner side, with a strongly-marked lobed cingulum, especially on the inner side, and slightly developed accessory cusps before and behind. The first and last upper and the first lower molar considerably smaller than the others. Vertebrae: C 7, D 15, I. 5, S 2, C11. All the nails of both fore and hind feet very small and rudimentary. One species, Μ. albiventer {Pelagius monachus of some authors), the Monk Seal of the Mediterranean and adjacent parts of the Atlantic.

The other genera of this section have the same dental formula, but are distinguished by the characters of the molar teeth and the feet. They are all inhabitants of the shores of the southern hemisphere.

Stenorhynchus {0gmorhinus, Peters).—All the teeth of the molar series with three distinct pointed cusps, deeply separated from each other; of these the middle or principal cusp is largest and slightly recurved; the other two (anterior and posterior) are nearly equal in size, and have their apices directed towards the middle one. Skull much elongated. One species, »S'. leptonyx, the Sea Leopard, widely distributed in the Antarctic and southern temperate seas.

Lobodon.— Molars with much-compressed elongated crowns, with a principal recurved cusp, rounded and somewhat bulbous at the apex, and with one anterior, and one, two, or three posterior, very distinct accessory cusps. One species, I.. carcinophaga. Leptonyx.— Molars small, with simple, subcompressed, conical crowns, with a’broad cingulum, but no distinct accessory cusps. I.. wcddellii. Ommatophoca.— All the teeth very small; those of the molar series with pointed recurved crowns, and small posterior andstιll less developed anterior accessory cusps. Orbits very large, Nails quite rudimentary on front and absent on hind feet. The skull bears a considerable resemblance to that of the membersof the next subfamily, towards which it may form a transition. There is one species, 0. rossii, of which very little is known.

Subfamily Cystophorinae.—Incisors ⅜. Teeth of molar senes-generally one-rooted. Nose of males with an appendage capable of being inflated. First and fifth toes of hind feet greatly exceeding the others in length, with prolonged cutaneous lobes, and rudimentary or no nails.

Cystophora.- Dentition: if, c⅜, p⅛, mf; total 30. The last molar has generally two distinct roots. Beneath the skin over the face of the male, and connected with the nostrils, is a sac capable of inflation, when it forms a kind of hood covering the upper part of the head. Nails present, though small on the hind feet. C. cristata, the Hooded or Bladder-Nose Seal of the Polar Seas.

Macrorhinus.— Dentition as the last, but molars of simpler character, and all one-rooted. All the teeth, except the canines, very small relatively to the size of the animal. Hind feet without nails. Vertebrae: C 7, D15, I. 5, S 4, C11. Nose of adult male produced into a short tubular proboscis, ordinarily flaccid, but capable of dilatation and elongation under excitement. One species, Μ. leonina, the Elephant Seal, or “Sea Elephant” of the whalers, the largest of the whole family, attaining the length of nearly 20 feet. Formerly abundant in the Antarctic Seas, and also found on the coast of California.

Extinct Pinnipeds.

Remains of animals of this group have been found in late Miocene and Pliocene strata in Europe and America, the most abundant and best preserved being those of the Antwerp Crags, the subject of a recent illustrated monograph by Van Beneden. Nothing has, however, yet been discovered which throws any light upon the origin of the group, as all the extinct forms at present known come within the definition of the existing families; and, though annectant forms between these occur, there are as yet no transitions to a more generalized type of mammal. Indeed, all those of which the characters are best known belong to the completely developed Phocine or Trichechine, not to the Otarine, type. The structure of the Pinnipeds is so clearly a modification of that of the terrestrial Carnivores, especially of the Arctoid type, that it is difficult to imagine that they can have had any other origin but one in common with that group; but the separation must have taken place early in the Tertiary epoch, if not before.

Bibliography of Pinnipedia.— J. A. Allen, History of North American Pinnipeds, 1880; P. J. Van Beneden, Ossements fossiles d'Anvers, pt. i., 1877.

Order PRIMATES.

This order in the system of Linnaeus includes Man, all the Monkeys, the Lemurs, and the Bats. By common consent of all zoologists the last-named animals have been removed into a distinct order. With regard to the association of the others, there has been, and still is, much difference of opinion.

That all the Monkeys, from the highest Anthropoid Apes to the lowest Marmosets, form a natural and tolerably homogeneous group seems never to have been questioned; but whether the Lemurs on the one hand and Man on the other should be united with them in the same order are points of controversy. With regard to the first, the question has already been referred to in the article Lemur, in which an account has been given of the characters and the principal modifications of the type. If, in accordance with the traditional views of zoologists, they are still considered to be members of the order Primates, they, must form a suborder apart from all the others, with which they have really very little in common except the opposable hallux of the hind foot, a character also met with in the Opossums, and which is therefore of very secondary importance.

The history of all the various forms of true Monkeys is very fully given in the article Ape. The position of Man alone remains to be considered. In the Systema Natur ae of Linnaeus he was separated only generically from the Apes, but in the next great work which exercised a widespread influence over the progress of zoological science, the Règne Animal of Cuvier, he forms a distinct order under the name of Bimana, the Monkeys and Lemurs being associated together as Quadrumana. This has been the prevailing arrangement in the zoological systems of the present century, though in the classification of Owen his position is still farther removed from that of the Monkeys, as in it the genus Homo forms one of the four primary divisions or subclasses of the Mammalia, called Archence-phala, the Quadr umana being united with the Carnivora, Ungulata, and others in another division called Gyrence-phala. On the other hand the tendency of most modern systematists, for reasons which have been fully stated by Professor Huxley, is to revert towards the Linnaean position. Considering solely the facts of Man’s bodily structure, it can be clearly demonstrated that the points in which he differs from the most nearly resembling Ape are not of greater importance than those by which that Ape differs from other universally acknowledged members of the group; and therefore, in any natural system, if Man is to be made a subject of zoological classification upon the same principles as those applied elsewhere, he must be included in the order which comprises the Monkeys. We say upon the same principles as are applied elsewhere, as zoological classification has never taken into consideration the psychological characteristics which distinguish the subjects of its investigations, but only their tangible and physical structure, otherwise endless confusion would result, at all events with our very imperfect knowledge of animal psychology. The essential attributes which distinguish Man, and give him a perfectly isolated position among living creatures, are not to be found in his bodily structure, and therefore should either be left entirely out of consideration or have such weight given to them as would remove him completely out of the region of zoological classification. To profess to classify Man as if he were one of the animals, as in all points of the structure and functions of his organs he undoubtedly is, to place him in the class Mammalia, and then to allow other considerations to influence the judgment as to the particular position he should occupy in the class, is most illogical.

Man, therefore, considered from a zoological point of view, must be included in the order Primates, even if the Lemurs are removed from it, as his structural affinities with the Monkeys are far closer than are those of the so-called “Half-Apes.” We may, without treading upon debateable ground, go farther, and say that the differences between Man and the Anthropoid Apes are really not so marked as those which separate the latter from the American Monkeys. Perhaps the best exposition of the facts relating to the present condition of the order will be a division into five sections, which may be considered as families, of course without intending to imply that they are exactly equivalent, or that the intervals which separate them are of precisely the same importance, but that they are five distinct groups, all branches from a common stem, and unconnected in the present condition of nature by any intermediate forms. These are—(1) Hominidae, containing Man alone; (2) Simiidae, containing the four genera of Man-like Apes: Troglodytes, Gorilla, Simia, and Hylobates; (3) Cercopithecidae, containing all the remaining Old-World Monkeys; (4) Cebidae, containing the American Monkeys having three true molar teeth on each side of each jaw; and (5) Hapalidεe,, the American Monkeys with two molar teeth, or Marmosets.

The distinctions between Hominidae, and Simiidae, of which alone we have to treat at present, as the characters of the other families are given in the article Ape, are chiefly relative, being greater size of brain and of brain case as compared with the facial portion of the skull, smaller development of the canine teeth of the males, more complete adaptation of the structure of the vertebral column to the vertical position, greater length of the lower as compared with the upper extremities, and greater length of hallux or great toe, with almost complete absence of the power of bringing it in opposition to the other four toes. The last and the small size of the canine teeth are perhaps the most marked and easily defined distinctions that can be drawn between the two groups.

Man is universally admitted to form a single genus, Homo of Linnaeus, but a question of considerable importance in treating of him from a zoological point of view, and one which has been a subject of much controversy, is whether all men should be considered as belonging to one or to several species. This question is perhaps of less importance now than formerly, when those who maintained a plurality of species associated with the hypothesis plurality of origin. One of the strongest arguments against the view that the various races of Man represent more than one species is that none of those who have maintained it have been able to agree as to how many distinct specific modifications can be defined, almost -every number from three to twenty or more having been advocated by different authors. If the distinguishing characters of the so-called species had been so marked, there could not be such a remarkable diversity of opinion upon them. Again, the two facts—(1) that, however different the extremes of any two races may be in appearance (and it must be admitted that, as advocated by many polygenists, the differences are greater than many which are considered specific among other animals), every intermediate gradation can be found through which the one passes into the other, and (2) that all races are fertile inter se— are quite conclusive in favour of considering Man as representing a single species in the ordinary sense in which the word is now used, and of treating of all his various modifications as varieties or races.

The great problem at the root of all zoology, the discovery of a natural classification which shall be an expression of our knowledge of the real relationship or consanguinity of different forms, is also applicable to the study of the races of Man. When we can satisfactorily prove that any two of the known groups of mankind are descended from the same common stock, a point is gained. The more such points we have acquired the more nearly shall we be able to picture to ourselves, not only the present, but the past distribution of the races of Man upon the earth, and the mode and order in which they have been derived from one another. But the difficulties in the way of applying zoological principles to the classification of Man are vastly greater than in the case of most animals. When groups of animals become so far differentiated from each other as to represent separate species, they remain isolated; they may break up into further subdivisions—in fact, it is only by further subdivision that new species can be formed; but it is of the very essence of species, as now universally understood by naturalists, that they cannot recombine, and so give rise to new forms. With the varieties of Man it is otherwise. They have never so far separated as to answer to the physiological definition of species. All races, as said above, are fertile with one another, though perhaps in different degrees. Hence new varieties have constantly been formed, not only by the segmentation of portions of one of the old stocks, but also by various combinations of those already established.

Without entering into the difficult question of the method of Man’s first appearance upon the world, we must assume for it vast antiquity,—at all events as measured by any historical standard. Of this there is now ample proof. During the long time he existed in a savage state—a time compared to which the dawn of our historical period is as yesterday—he was influenced by the operation of those natural laws which have produced the variations seen in other regions of organic nature. The first Men may very probably have been all alike; but, when spread over the face of the earth, and become subject to all kinds of diverse external conditions,—climate, food, competition with members of his own species or with wild animals,—racial differences began slowly to be developed through the potency of various kinds of selection acting upon the slight variations which appeared in individuals in obedience to the tendency planted in all living things. These differences manifested themselves externally in the colour of the skin, the colour, quality, and distribution of the hair, the form of the head and features, and the proportions of the limbs, as well as in the general stature.

Geographical position must have been one of the main elements in determining the formation and permanence of races. Groups of Men isolated from their fellows for long periods, such as those living on small islands, to which their ancestors may have been accidentally drifted, would naturally, in course of time, develop a new type of features, of skull, of complexion, or hair. A slight set in one direction, in any of these characters, would constantly tend to intensify itself, and so new races would be formed. In the same way, different intellectual or moral qualities would be gradually developed or transmitted in different groups of Men. The longer a race thus formed remained isolated, the more strongly impressed and the more permanent would its characteristics become, and less liable to be changed or lost* when the surrounding circumstances were altered, or under a moderate amount of intermixture from other races—the more “true” in fact, would it be. On the other hand, on large continental tracts, where no mountain ranges or other natural barriers form obstacles to free intercourse between tribe and tribe, there would always be a tendency towards uniformity, from the amalgamation of races brought into close relation by war or by commerce. Smaller or feebler races would be destroyed or absorbed by others impelled by superabundant population or other causes to spread beyond their original limits; or sometimes the conquering race would itself disappear by absorption into the conquered.

Thus, for untold ages, the history of Man has presented a shifting, kaleidoscopic scene: new races gradually becoming differentiated out of the old elements, and, after dwelling a while upon the earth, either becoming suddenly annihilated or gradually merged into new combinations; a constant destruction and reconstruction; a constant tendency to separation and differentiation, and a tendency to combine again into a common uniformity—the two tendencies acting against and modifying each other. The history of these processes in former times, except in so far as they may be inferred from the present state of things, is a difficult study, owing to the scarcity of evidence. If we had any approach to a complete palaeontological record, the history of Man could be reconstructed; but nothing of the kind is forthcoming. Evidence of the anatomical characters of Man, as he lived on the earth during the time when the most striking racial characteristics were being developed, during the long ante-historic period in which the Negro, the Mongolian, and the Caucasian were being gradually fashioned into their respective types, is entirely wanting, or if any exists it is at present safely buried in the earth, perhaps to be revealed at some unexpected time and in some unforeseen manner. Even the materials from which a history of the modifications of the human species as known to our generation must be constructed are rapidly passing away, as the age in which we live is an age in which, in a far greater degree than any previous one, the destruction of races, both by annihilation and absorption, is going on. Owing to the rapid extension of maritime discovery and commerce, changes such as have never been witnessed before are now taking place in the ethnology of the world, changes especially affecting the island populations among which, more than elsewhere, the solution of many of these problems may be looked for. The subject is, however, attracting the attention of observers of all countries to a greater degree than it ever has before, with the usual result of bringing distrust upon, and dissatisfaction with, the old systems, without as yet establishing anything in their place which meets with universal acceptance. The difficulty of finding distinctive characters capable of strict definition by which races or groups may be differentiated may be inferred from what has been said above. It is rather by the preponderance of certain characters in a large number of members of a group than by the exclusive or even constant possession of these characters in each of its members that the group must be distinguished. Hence, in all cases in which the characters can be expressed by the numerical method, as in the dimensions and proportions of different parts of the body, averages are now largely used by anthropologists. Provided the data upon which these averages are based have been obtained from a sufficient number of individuals, they can be absolutely relied upon to express the prevailing or most characteristic development of each particular feature in any group, and permit satisfactory comparisons between the conditions of that feature in different groups. Great progress is now being made in perfecting the methods of investigation of racial characteristics, and as we are beginning to learn what lines of research are profitable and what are barren, we may hope that the time is not far distant when we may get some clear insight into the knowledge of the natural classification and relationships of the races of Man. fw. h. f.) Index. [table] [table] [table] [table] [table] [table]