Reptiles

REPTILES

ANTELINAeAN writers comprised the animals which popularly are known as Tortoises and Turtles, Crocodiles, Lizards and Snakes, Frogs and Toads, Newts and Salamanders, under the name of Oviparous Quadrupeds or four-limbed animals which lay eggs. Linnaeus, desirous of giving expression to the extraordinary fact that many of these animals pass part of their life in the water and part on land, substituted the name of Amphibia for the ancient term. Subsequent French naturalists (Lyonnet and Brisson ) considered that the creeping mode of locomotion was a more general characteristic of the class than their amphibious habits, and consequently proposed the scarcely more appropriate name of Reptiles.

As naturalists gradually comprehended the wide gap existing between Frogs, Toads, ¿c., on the one hand, and the other Oviparous Quadrupeds on the other, they either adopted the name of Batrachia for the former and that of Amphibia for the latter, or they restricted the term Amphibia to Batrachians, calling the remainder of these creatures Reptiles. Thus the term Amphibia , as used by various authors, may apply (1) to all the various animals mentioned, or (2) to Batrachians only—and thus it has been used in the article Amphibia in the present work. The term Reptiles is used (1) by some for all the animals mentioned above, and (2) by others, as in the present article, for the same assemblage of animals after the exclusion of Batrachians. Other terms more or less synonymous with Amphibians and Reptiles in their different senses have been used by the various systematists, as we shall see hereafter.

Equally varying are the limits of the term “Saurians,” which occurs so frequently in every herpetological treatise. At first it comprised living Crocodiles and Lizards only, with which a number of fossil forms were gradually associated. As the characters and affinities of the latter became better known, some of them were withdrawn from the Saurians, and at present it is best to abandon the term altogether.

History and Literature.

a. The General Subject.

By some feature of their organization or some peculiarity in their economy Reptiles have always forced themselves upon the observation of man or excited his imagination, so that certain kinds are mentioned in the earliest written records or have found a place among the fragments of the oldest relics of human art. Such evidences of a popular knowledge of Reptiles, however, form no part of a succinct review of the literature of the subject such as it is proposed to give here. We distinguish in it five periods :—(1) the Aristotelian; (2) the Linnaean (formation of a class Amphibia , in which Reptiles and Batrachians are mixed); (3) the period of the elimination of Batrachians as one of the Reptilian orders (Brongniart); (4) that of the separation of Reptiles and Batrachians as distinct subclasses; (5) that of the recognition of a class Reptilia as part of the Sauropsida (Huxley).

1. The Aristotelian Period. —As in other branches of Ar zoology, we have to start with Aristotle, who was the first to deal with the Reptiles known to him as members of a distinct portion of the animal kingdom, and to point out the characteristics by which they resemble each other and differ from other vertebrate and invertebrate animals. As the plan of his work, however, was rather that of a comparative treatise of the anatomical and physiological characters of animals than their systematic arrangement and definition, his ideas about the various groups of Reptiles are not distinctly expressed, but must be gleaned from the terms which lie employs. And even when we make due allowance for the fact that we are in possession of only a part of his writings, we cannot but perceive that he paid less attention to the study of Reptiles than to that of other classes; this is probably due to the limited number of kinds with which he could be acquainted from the fauna of his own country, and to which only very few extra-European forms, like the Crocodile, were added from other sources. And, whilst we find in some respects a most remarkable accuracy of knowledge, there is sufficient evidence that lie neglected every-day opportunities of information, as if Reptiles had not been a favourite study. Thus, lie has not a single word about the metamorphoses of Batrachians, which he treats of in connexion with Reptiles.

Aristotle makes a clear distinction between the scute or scale of a Reptile, which he describes as <£oXts, and that of a Fish, which lie designates as Xen-is. He mentions Reptiles (1) as oviparous quadrupeds with scutes, viz., Saurians and Chelonians; (2) as oviparous apodals, viz., Snakes; (3) as oviparous quadrupeds without scutes, viz., Batrachians. He considered the first and second of these three groups as much more nearly related to each other than to the third. He says: —

“The genus of Snakes resembles that of Lizards, nearly all the characters being common to both, if the Lizard be conceived of as prolonged and without legs. They possess scutes, and are similar to Lizards above and below, but they lack testicles; and, like Fishes, they possess two excretory ducts which coalesce, and the uterus is large and bipartite. In other respects their internal parts are like those of Lizards, save that all the intestines are long and narrow. The tongue is narrow, long, black, and very exsertile. It is a peculiarity of Snakes and Lizards that they possess a bifid tongue; but the points of the tongue of Snakes are fine like hairs. All Snakes are “carcharodont” (have acute teeth); they have as many ribs as there are days in the month, viz., 30. Some say that Snakes recover the loss of an eye; the tail is reproduced in Lizards and Snakes when cut off,” &c.

Thus accurate statements and descriptions are sadly mixed with errors and stories of, to our eyes, the most absurd and fabulous kind. The most complete accounts are those of the Crocodile (chiefly borrowed from Herodotus) and of the Chameleon, which Aristotle evidently knew from personal observation, and which he had dissected himself. The other Lizards mentioned by him are the common Lizards ( σαύρα ), the common Seps (χαλκίς or ζιγνίς), and the Gecko (άσ־καλ αβωτης or κορΒνλος). Of Snakes (of which he generally speaks as οφίζ) he knew the Yipers («fyi9 or εχιδνα), the common Snake ( v8po <;), and the Blindworm (τνφλίνης οφις), which he regards as a Snake; he further mentions the Egyptian Cobra and Dragons (δράκων)—North-African Serpents of fabulous size. Of Chelonians he describes in a perfectly recognizable manner Land Tortoises (χελώνη), Freshwater Turtles (έμνς), and Marine Turtles (χελώνη η θαλαττία).

Passing over eighteen centuries we find the knowledge of Reptiles to have remained as stationary as other branches of natural history, perhaps even more so. The Reptile fauna of Europe was not extensive enough to attract the energy of a Belon or Rondelet; popular prejudice and the difficulty of preserving these animals deterred from their study; nor was the mind of man sufficiently educated not to give implicit credence to the fabulous tales with which every account of Reptiles in the 15th and 16th centuries was replete. The art of healing, however, was developing into a science based upon rational principles, and consequently not only those Reptiles which formed part of the materia medica but also the venomous Snakes became objects of study to the physician. Snakes, and especially the Viper, were treated of in distinct divisions of general works, or in separate monographs. It is true that these treatises were written less with the view of elucidating the natural history of the animals than with that of describing their poisonous nature and indicating the manner in which they should be used as medicaments, the majority of the writers being ignorant of the structure of the venom-apparatus, and of the distinction between non-venomous and venomous Snakes.

Nothing can show more clearly the small advance made by herpetology in this long post-Aristotelian period than a glance at the celebrated work, De Differentiis Animalium Libri decern (Paris, 1552), by Edward Wotton (1492-1555). Wotton treats of the Reptiles which he designates as Quadrupedes oviparx et Serpentes in the sixth book of his work. They form the second division of the Quadrupedes qux sanguinem habent, and are subdivided in the following “genera” :—

Crocodilus etscincus (cap. cv.); Testudinum genera (cvi.); Ran-arum genera (cvii.); Lacertx (cviii.); Salamandra et seps quad-rupee (cix.); Stellio (cx.); Chamxleo (cxi.); Serpentes (cxii.), a general account, the following being different kinds of Serpents: —Hydrus et alii quidam serpentes aquatiles (cxiii.); Serpentes terrestres et primo aspidum genera (cxiv.); Vipera, dipsas, cerastes, et hammodytes (cxv. ); Hxmorrlius, sepedon, seps, cenchris, et cenchrites (cxvi.); Basiliscus et alii quidam serpentes quorum venenum remedio caret (cxvii.); Draco, amphishxna, et alii quidam serpentes quorum morsus minus affert periculi (cxviii.).

As regards the treatment of the subject, Wotton’s work might with propriety be termed “Aristoteles redivivus.” The plan is the same, and the observations of the Greek naturalist are faithfully, sometimes literally, reproduced. It is surprising that even the Reptiles of his native country were most imperfectly known to the author.

A new impetus for the cultivation of the study of natural history was given through the observations and writings of travellers in India, Africa, and America. With the enlargement of geographical knowledge that of Reptiles was also advanced, as is sufficiently apparent from the large encyclopaedic works of Gesner, Aldrovandi, and J ohnston. The last-named author especially, who published the various portions of his natural history in the middle of the 17th century, was able to embody in his compilations notices of numerous Reptiles observed by Francisco Hernandez in Mexico and by Marcgrave and Piso in Brazil. As the author had no definite idea of the Ray-Linnsean term “species,” it is not possible to give the exact number of Reptiles mentioned in his work. But it may be estimated at about fifty, not including some marine fishes and fabulous creatures. He figures (or rather reproduces the figures of) about forty,—some species being represented by several figures.

2. Linnxan Period: Formation of a Class Amphibia .— Within the century which succeeded these compilatory works (1650-1750) fall the labours which prepared the w r ay for and exerted the greatest influence on Ray and Linnaeus. Although original researches in the field ol herpetology were limited in extent and in number, the authors had freed themselves from the purely literary oi scholastic tendency. Men were no longer satisfied wit! reproducing and commenting on the writings of their predecessors; the pen was superseded by the eye, the micro scope, and the knife, and statements were tested by experiment. This spirit of the age manifested itself, sc far as the Reptiles are concerned, in Chara’s and Redi’s admirable observations on the Yiper, in Major’s and Val lisnieri’s detailed accounts of the anatomy of the Chamte leon, in the researches of Jacob.eus into the metamor phoses of the Batrachians and the structure of Lizards, ir Dufay’s history of the development of the Salamander (foi Batrachians are invariably associated with Reptiles proper) in Tyson’s description of the anatomy of the Rattlesnake <fec. The natural history collections formed by institution! and wealthy individuals now contained not merely skin! of Crocodiles or Serpents stuffed and transformed into i shape to correspond with the fabulous descriptions of tin ancient dragons; but, with the discovery of alcohol as i means of preserving animals, Reptiles entire or dissectec were exhibited for study; and no opportunity was lost o obtaining them from travellers or residents in foreigr countries. Fossils also were now acknowledged to be re mains of animals which had lived before the flood, anc some of them were recognized as those of Reptiles.

The contributions to a positive knowledge of the anima kingdom became so numerous as to render the need of £ methodical arrangement of the abundance of new facts more and more pressing. Of the two principal systematic attempts made in this period the first ranks as one of the most remarkable steps of the progress of natural history whilst the second can only be designated as a signal failure, which ought to have been a warning to all those who in aftei years classified animals in what is called an “artificial system.” As the latter attempt, originating with Klein (1685-1759), did not exercise any further influence on herpetology, it will be sufficient to have merely mentioned it. John Ray (1628-1705) had recognized the necessity of introducing exact definitions for the several categories into which the animals had to be divided, and he maintained that these categories ought to be characterized by the structure of animals, and that all zoological knowledge had to start from the “ species” as its basis. His definition of Reptiles as “animalia sanguinea pulmofie respirantia cor unico tantum ventriculo instructum habentia ovipara” fixed the class in a manner which was adopted by the naturalists of the succeeding hundred and fifty years. Nevertheless, Ray was not a herpetologist; he never made these animals his special study, as is evident from the way in which he subdivides the class, as well as from his imperfect treatment of the species. His knowledge of Reptiles is chiefly derived from the researches of others, from whose accounts, however, everything not based upon reliable demonstration is critically excluded. He begins with a chapter treating of Frogs (Dana, with two species), Toads ( Bufo , with one species), and Tortoises

( Testudo, with fourteen species). The second group comprises the Lacertse, twenty-live in number, and includes the Salamander and Newts; and the third the Serpentes, nine species, among which the Limbless Lizards are enumerated.

Except in so far as he made known and briefly characterized a number of Reptiles, our knowledge of this class was not advanced by Linn.eus. His notions as to the relation of the various types among themselves and to the other vertebrates were the same as those of Ray, and the progress made by herpetology in the various editions of the Systema Nature¿ is therefore of a merely formal character. That Linnaeus associated in the 12th edition cartilaginous and other Fishes with the Reptiles under the name of Amphibia Nantes was the result of some misunderstanding of an observation by Garden, and is not to be taken as a premonitory token of the recent discoveries of the relation between Batrachians and Fishes. Linnaeus places Reptiles, which he calls Amphibia , as the third class of the animal kingdom; he divides the genera thus :—

Order 1. Reptiles. —Tcstudo (15 species); Rana (17 sp.); Draco (2 sp.); Lacerta (48 sp., including 6 Batrachians).

Order 2. Serpentes. — Crotalus (5 species); Boa (10 sp.); Coluber (96 sp.); Anguis (15 sp.); Arnphisbxna (2 sp.); Csecilia (2sp.).

None of the naturalists who under the direction or influence of Linnaeus visited foreign countries possessed any special knowledge of or predilection for the study of Reptiles; all, however, contributed to our acquaintance with tropical forms, or transmitted well-preserved specimens to the collections at home, so that Gmelin, in the 13th edition of the Systema Natures, was able to enumerate three hundred and seventy-one species.

The man who, with the advantage of the Linnaean method, first treated of Reptiles monograpliically, was Laurenti. In a small book he proposed a new division of these animals, of which some ideas and terms have survived into our times, characterizing the orders, genera, and species in a much more precise manner than Linnaeus, giving, for his time, excellent descriptions and figures of the species of his native country. Laurenti might have become for herpetology what Artedi was for ichthyology, but his resources were extremely limited. He himself complains that he had no literary intercourse with foreign naturalists, and access to but a few works (he especially mentions Seba’s Thesaurus) and one collection only,

The circumstance that Chelonians are entirely omitted from his Synopsis seems due rather to the main object with which he engaged in the study of herpetology, viz., that of examining and distinguishing Reptiles reputed to be poisonous, and to want of material, than to his conviction that Tortoises should be relegated to another class. He divides then the class into three orders :—

T. Salientia, with the genera Pipa, Bufo, Rana, Hyla, and one species of “Proteus,” viz., the larva of Pseudisparadoxa.

Gradientia, the three first genera of which are Tailed Batrachians, viz., two species of Proteus (one being the P. anguinus), Triton, and Salamandra ; followed by true Saurians— Caudiverbera, Gecko, Cha.mselco, Iguana, Basiliscus, Draco, Cordylus, Crocodilus, Scincus, Stellio, Seps.

3. Serpentia, among which ho continues to keep Amphisbsena, Csecilia, and Anguis, but the large Linnaean genus Coluber is divided into twelve, chiefly from the scutellation of the head and form of the body.

The work concludes with an account of the experiments made by Laurenti to prove the poisonous or innocuous nature of those Reptiles of which he could obtain living specimens.

The next general work on Reptiles is by Lacépède. It appeared in the years 1788 and 1790 under the title Histoire Naturelle des Quadrupèdes Ovipares et des Serpens (Paris, 2 vols. 4to). Although as regards treatment of details and amount of information this work far surpasses the modest attempt of Laurenti, it show's no advance towards a more natural division and arrangement of the genera. The author depends entirely on conspicuous external characters, and classifies the Reptiles into (1) oviparous quadrupeds with a tail, (2) oviparous quadrupeds without a tail, (3) oviparous bipeds ( Chirotes and Pseudopus), (4) Serpents,—an arrangement in which the old confusion of Batrachians and Reptiles and the imperfect definition of Lizards and Snakes are continued, and which it is worthy of remark we find also adopted in Cuvier’s Tableau Élémentaire de l’Histoire Naturelle des Animaux (1798), and nearly so by Latreille in his Histoire Naturelle des Reptiles (Paris, 1801, 4 vols. 12mo). Lacépède’s monograph, however, remained for many years deservedly the standard work on Reptiles, on account of the ability with which the author collected all reliable information on the various species, and on account of the facilities which it afforded for determining them. The numerous plates with which the work is illustrated are, for the time, well drawn, and the majority readily recognizable.

3. The Period of Elimination of Batrachians as one of the Reptilian Orders. —A new period for herpetology com- mences with Alex. Brongniart, who in 1799 first recognized the characters by which Batrachians differ from the other Reptiles, and by which they form a natural passage to the class of Fishes. Csecilia (as also Langaha and Acrochordus) is left by Brongniart with hesitation in the order of Snakes, but Newts and Salamanders henceforth are no more classed with Lizards. He leaves the Batrachians, however, in the class of Reptiles as the fourth order. The first order comprises the Chelonians, the second the Saurians (including Crocodiles and Lizards), the third the Ophidians—terms which have been adopted by all succeeding naturalists. Here, however, Brongniart’s merit on the classification of Reptiles ends, the definition and disposition of the genera remaining much the same as in the works of his predecessors.

The activity in France in the field of natural science I was at this period, in spite of the political disturbances, so great that only a few years after Lacépède’s work another, almost identical in scope and of the same extent, appeared, viz., the Histoire Naturelle Générale et Particulière des Reptiles of F. M. Daudin (Paris, 1802-3, 8 vols. 8vo). Written and illustrated with less care than that by Lacépède, it is of greater importance to the herpetologists of the present day, as it contains a considerable number of generic and specific forms described for the first time. Indeed, at the end of the work, the author states that he has examined more than eleven hundred specimens, belonging to five hundred and seventeen species, all of which he has described from nature. The system adopted is that of Brongniart, giving to the work a character by which the modern herpetologist is most favourably impressed. The genera are well defined, but ill arranged; it is, however, noteworthy that Csecilia takes now its place at the end of the Ophidians, and nearest to the succeeding order of Batrachians.

The next step in the development of the herpeto-logical system was the natural arrangement of the genera. This involved a stupendous amount of labour; by a careful thorough examination of all the types of Reptiles then known, reliable characters had to bo discovered, and by means of the principle of the subordination of characters the genera had to be grouped into families within Brongniart’s orders. Although many isolated contributions were made by various workers, this task could be successfully undertaken and completed in the Paris Museum only, in which, besides Seba’s and Lacepede’s collections, many other herpetological treasures from other museums had been deposited by the victorious generals of the empire, and to which through Cuvier’s reputation objects from every part of the world were attracted in a more peaceful and voluntary manner. The men who , devoted themselves to this task were A. M. C. Dumeril, Oppel, and Cuvier himself. It is the duty of the biographer rather than the historian to ascertain what share of the merit in building up the new system should be allotted to each of these three. Oppel was a German who, during his visit to Paris (1807-8), attended the lectures of Dumeril and Cuvier, and at the same time studied the materials to which access was given to him by the latter in the most liberal manner. Dumeril maintains that Oppel’s ideas and information were entirely derived from his lectures, and that Oppel himself avows this to be the case. The passage, however, to which he refers is somewhat ambiguous; and it is certain that there is the greatest possible difference between the arrangement published by Dumeril in 1806 (Zoologie Analytique, Paris, 8vo) and that proposed by Oppel in his Ordnun-gen, Familien, und Gattungen der Reptilien (Munich, 1811, 4to). There is no doubt that Oppel profited largely by the teaching of Dumeril; but, on the other hand, there is sufficient internal evidence in the works of both authors, not only that Oppel worked independently, but also that Dumeril and Cuvier owed much to their younger fellow-labourer, as Cuvier himself indeed acknowledges more than once.

Oppel’s classification may be shortly indicated thus:— Order 1. TESTUDINATA or CH^LONIENS.

Fam. 1. Chelonii (gen. Mydas, Coriacca).

Fam. 2. Amyiee (gen. Trionyx, Chelys, Testudo, Emys). Order 2. SQUAMATA.

Sect. A. Saurii.

Fam. 1. Crocodilini (gen. Crocodilus, Gavialis, Alligator'}.

Fam. 2. Geckoides (gen. Gecko, Stellio, Agama).

Fam. 3. Iguanoidf.s (gen. Camseleo, Draco, Iguana, Basiliscus, Lophyrus, Anolis).

Fam. 4. Lacertini (gen. Tupinambis, Dracaena, Lacerta, Tachy-dromus).

Fam. 5. Scincoides (gen. Scincus, Seps, Scheltopusik, Anguis). Fam. 6. Chalcidici (gen. Chalcides, Bimanus, Bipcs, Ophi- saurus).

Sect. B. OrniDir.

Fam. 1. Anguiformes (gen. Tortrix, Amphisbxna, Typhlops). Fam. 2. Constrictores (gen. Boa, Eryx).

Fam. 3. Hydri (gen. Platurus, Hydrophis).

Fam. 4. Pseudo-vipera: (gen. Acrochordus, Erpetori}.

Fam. 5. Crotalini (gen. Crotalus, Trigonocephalus).

Fam. 6. Viperini (gen. Eipera, Pseudoboa}.

Fam. 7. Colurrtni (gen. Coluber, Bungarus). Order 3. NUDA or BATRACII.

In this classification we notice three points, which indicate a decided progress towards a natural system. (1) The four orders proposed by Brongniart are no more considered cosubordinate in the class, but the Saurians and Ophidians are associated as sections of the same order, a view held by Aristotle but abandoned by all following naturalists. The distinction between Lizards and Snakes is carried out in so precise a manner that one genus only, Amphisbsena, is wrongly placed. (2) The true Reptiles have now been entirely divested of all heterogeneous elements by relegating positively Caecilia to the Batrachians, a view for which Oppel had been fully prepared by Duméril, who pointed out in 1807 that “les cécilies se rapprochent considérablement des batraciens auxquels elles semblent lier l’ordre entier des serpens.” (3) An attempt is made at arranging the genera into families, some of which are still retained at the present day.

In thus giving a well-merited prominence to Oppel’s labours, we are far from wishing to detract from the influence exercised by the master spirit of this period, Cuvier. Without his guidance Oppel probably never would have found a place among the promoters of herpetological science. But Cuvier’s principal researches on Reptiles were incidental or formed part of some more general plan; Oppel concentrated his on this class only. The latter acquired a more correct view as regards the higher divisions, while Cuvier was enabled by a more detailed study of the genera to define certain families more precisely and arrange them in a more natural manner, and to add not a few to the generic forms. Cuvier adopts the four orders of Reptiles proposed by Brongniart as equivalent elements of the class, and restores the Blind-worms and allied Lizards, and, what is worse, also the Csecilias, to the Ophidians. The Chamaeleons and Geckos are placed in separate groups, and the mode of dividing the latter has been retained to the present day. Also a natural division of the Snakes, although the foreign elements mentioned are admitted into the order, is sufficiently indicated by his arrangement of the “vrais serpens proprement dits” as (1) non-venomous Snakes, (2) venomous Snakes with several maxillary teeth, and (3) venomous Snakes with isolated poison-fangs. Without entering into those long descriptions of the species which continue to be the bane of modern zoology, he distinguishes the species of Reptiles with a precision not attained in any previous work, critically examining the literature and adding the principal references.

Cuvier’s researches into the osteology of Reptiles had not only the object of forming the basis for their arrangement, but also of discovering the means of understanding the fossil remains which now claimed the attention of French, English, and German naturalists. Extinct Chelo-nian and Crocodilian remains, Pterodactylus, Ilosasaurus, Iguanodon, Ichthyosaurus, Teleosaurus, became the subjects of Cuvier’s classical treatises which form the contents of. the 5 th volume (part 2) of his Recherches sur les Ossemens Fossiles, oà Von rétablit les caractères des plusieurs animaux dont les révolutions du globe ont détruit les espèces (new ed., Paris, 1821, 4to).

All the succeeding herpetologists adopted either Oppel’s or Cuvier’s view as to the number of orders of Reptiles, or as to the position Batrachians ought to' take in their relation to Reptiles proper, with the single exception of D. de Blainville. He divided the “oviparous subtype” of Vertebrates into four classes, Birds, Reptiles, Amphibians, and Fishes, a modification of the system which is all the more significant as he designates the Reptiles “Squammifères Ornithoides, écailleux,״ and the Amphibians “Nudipellifères, Ichthyoides nus.” In these terms we perceive clear indications of the relations which exist to the class of Birds on the one hand, and to that of Fishes on the other; they are signs which cast their shadow before them, but, unfortunately, Blainville himself did not follow up the ideas thus expressed, and abandoned even the terms in a later edition of liis systematic tables.

The direct or indirect influence of the work of French anatomists manifested itself in the systems of the other herpetologists of this period. The Crocodiles, especially, which hitherto (strange to say, even in Cuvier’s classification) had been placed as one of the families of Saurians, now commence to be separated from them. Merrem ( Verstick eines Systems der Amphibien, Marburg, 1820, 8vo) distinguishes two classes of “Amphibians,” Pho-lidota and Batrachia.

The Pholidota (or Reptiles) are divided into three orders, distinguished chiefly by osteological and splanchnological characters:—

1. Testudinata;

2. Louicata (= Crocodiles);

3. Squamata ( = Oppel’s Squamata, excluding Crocodiles).

Merrem’s subdivision of the Squamata into (1) Gradientia

( = limbed Lacertilia), (2) Repentia (=limbless Lacertilia), (3) Serpcntia (־־Snakes and Amphisbsena), (4) Incedentia (= Chirotes), and (5) Predentia ( ־־ Chamseleons) was based chiefly on the modifications of the limbs, and not adopted by his successors. The greater part of his work is occupied with a synopsis of all the species of Reptiles known, each being shortly characterized by a diagnosis; but, as only a small proportion (about one hundred and seventy) were known to him from autopsy, this synopsis has all the faults of a compilation.

Latreille, who commenced the study of. Reptiles as early as 1801, had kept pace with the progress of science when he published, in 1825, his Families Nciturelles du Regne, Animal (Paris, 1825, 8vo). He separated the Batrachians as a class from the Reptiles, and the latter he divides into two sections only, Cataphracta and Squamosa ,— in the former Crocodiles being associated with the Che-lonians. He bases this view on the development of a carapace in both, on the structure of the feet, on the fixed quadrate bone, on the single organ of copulation. None of the succeeding herpetologists adopted a combination founded on such important characters except J. E. Gray, who, however, destroyed Latreille’s idea of Cataphracta by adding the Amphisbaenians as a third order.

Cuvier’s account of the genera and species of Reptiles in the Regne Animal was too succinct, and Merrem’s bore too much the character of a compilatory list, to furnish efficient aid in the arrangement of the mass of new materials which began to accumulate from all parts of the world in European museums. Among others, Spix had brought from his travels in Brazil a rich spoil to the Munich Museum, and the Bavarian Academy charged Joh. Wagler, who was engaged in working out these materials, to prepare a general system of Reptiles and Batrachians. His work, the result of ten years’ labour, is a simple but lasting monument to a young naturalist, who, endowed with an ardent imagination, only too frequently misinterpreted the evidence of facts, or forced it into the service of preconceived ideas. Cuvier had drawn attention to certain resemblances in some parts of the osseous structure of Ichthyosaurus and Pterodactylus to Dolphins, Birds, Crocodiles, «fee. Wagler, seizing upon such analogical resemblances, separated those extinct Saurians from the class of Reptiles, and formed of them and the Monotremes a distinct class of Vertebrates, intermediate between Mammals and Birds, which he called Gryphi. When we consider that the discovery of the mode of propagation of the Monotremes is probably reserved for the present decennium, and that the propagation of those extinct Reptiles may remain an unsolved mystery, we must admit that Wagler has made free use of his imagination by defining his class of Gryphi as “vertebrates with lungs lying free in the pectoral cavity; oviparous; development of the embryo (within or) without the parent; the young fed (or suckled!) by the parents.” By the last character this Waglerian class is distinguished from the Reptiles.

Reptiles (in which Wagler includes Batrachians) are divided into eight orders :— Testudines, Crocodili, Lacertse, Serpentes, Angues, Csecilioe, Ranse, and Ichthyodi. He has great merit in having employed, for the subdivision of the families of Lizards, the structure of the tongue and the mode of insertion of the teeth in the jaws. On the other hand, however well the genera of Snakes are defined by him—and their number has been increased to ninety-six— Wagler has entirely failed in arranging them in natural families, venomous and non-venomous types being mixed in the majority of his groups.

L. Fitzinger was Wagler’s contemporary; his first work preceded Wagler’s system by four years. As he says in the preface, his object was to arrange the Reptiles in “a natural system, a system in which the objects are arranged in accordance with their greatest similarity, with their natural affinities. Such a system is a faithful image of the gradual progress of nature, expressed in words.” Unfortunately, in order to attain this object, Fitzinger paid regard to the most superficial points of resemblance; and in the tabula affinitatum generum which he constructed to demonstrate “the progress of nature” he has been much more successful in placing closely allied generic forms in contiguity than in tracing the relationships of the higher groups. That table is prepared in the form of a genealogical tree, but Fitzinger wished to express thereby merely the amount of morphological resemblance, and there is no evidence whatever in the text that he had a clear idea of genetic affinity. The Batrachians are placed at the bottom of the scheme, leading through llyla to the Geckos (clearly on account of the digital dilatations) and through Gsecilia to Amphisbsena. At the top Draco leads through Pterodactylus to the Bats (Pieropus), Ichthyosaurus to the Cetaceans ( Delphinus ), Ernys to the Monotremes, Testudo to Manis , and the Marine Turtles to the Divers and Penguins.

In Fitzinger’s system the higher groups are, in fact, identical with those proposed by Merrem, while greater originality is shown in the subdivision of the orders. He differed also widely from Wagler in his views as to the relations of the extinct forms. The order of Loricata consists of two families, the Ichthyosauroidea and Crocodiloidea, the former comprising Iguanodon, Plesiosaurus, Saurocephalus, and Ichthyosaurus. In the order Squamata Lacer-tilians and Ophidians are combined and divided into twenty-two families, almost all based on the most conspicuous external characters: the first two, viz., the Geckos and Chamseleons, are natural enough, but in the three following Iguanoids and Agamoids are sadly mixed, Pterodactyles and Draco forming one family; Mcgalosaums, Mosasaurus, Varanus, Tcjus, he., are associated in another named Ameivoidea; the Amphisbsenidse are correctly defined; the Colubroidea are a heterogenous assemblage of thirty genera; but with his family of Bungaroidea Fitzinger makes an attempt to separate at least a part of the venomous Colubrine Snakes from the Viperines, which again are differentiated from the last family, that of Crotaloidea.

There is sufficient evidence in this early publication that Fitzinger had at that time a good eye for seizing upon those characters by which the creation of small groups, such as genera, is regulated, and if this little work had been his only performance in the field of herpetology his name would have been honourably mentioned among his fellow-workers. But the promise of his early labours was not justified by his later work, and if we take notice of the latter here it is only because his name has become attached to many a Reptile through the pedantic rules of zoological nomenclature. The labours of Wiegmann, Müller, Duméril, and Bibron exercised no influence on him, and when he commenced to publish a new system of Reptiles in 1843, of which fortunately one fasciculus only appeared, he exhibited a classification in which morphological facts are entirely superseded by fanciful ideas of the vaguest kind of physiosophy, each class of vertebrates being divided into five “sense” series, and each series into three orders, one comprising forms of superior, the second of medium, and the third of inferior development. In the generic arrangement of the species, to which Fitzinger devoted himself especially in this work, he equally failed to advance science. From a superficial study of such species as were accessible to him, but chiefly from the descriptions of other authors, he selected any characters for the establishment of genera, and, abandoning entirely the value of a genus as a systematic category, he introduced a number of names, under the cloak of which he hid the superficiality of his work; many were adopted by his successors, who, however, had to substantiate their validity by a deeper study of the taxonomic characters.

We have now arrived at a period distinguished by the appearance of a work which, by the ability of its authors, by the comprehensiveness of its scope, by the treatment of the general subject as well as of the details, superseded all its predecessors, which formed the basis for the labours of many succeeding years, and which will always remain one of the classical monuments of descriptive zoology, — the Erpétologie Générale ou Histoire Naturelle complète des Reptiles of A. M. C. Duméril and G. Bibron (Paris, 8vo). The first volume appeared in 1834, and the ninth and last in 1854. No naturalist of that time could have been better qualified for the tremendous undertaking than C. Duméril, who almost from the first year of half a century’s connexion with the then largest collection of Reptilia had chiefly devoted himself to their study. The task would have been too great for the energy of a single man; it was, therefore, fortunate for Duméril that he found a most devoted fellow-labourer in one of his assistants, G. Bibron, whose abilities equalled those of the master, but who, to the great loss of science, died (in 1848) before the completion of the work. Duméril had the full benefit of Bibron’s knowledge for the volumes containing the Snakes, but the last volume, which treats of the Tailed Batrachians, had to be prepared by Duméril alone.

The work is the first which gives a comprehensive scientific account of Reptiles generally, their structure, physiology, and literature. Nearly the whole of the first volume is devoted to these chapters. And again each of the four orders admitted by the authors is introduced by a similar general account. In the body of the work 121 Chelonians, 468 Saurians, 586 Ophidians, and 218 Batra-chians are described in detail and with the greatest precision, On the principles of arrangement of the various orders we shall have to speak subsequently, and we mention here only that, singularly enough, the authors revert to Brongniart’s arrangement, in which the Batrachians are co-ordinate with the other three orders of Reptiles. This must appear all the more strange as Von Baer in 1828, and J. Müller in 1831, had urged, besides other essential differences, the important fact that no Batrachian embryo possesses either an amnion or an allantois, like a Reptile.

4. Period of the Separation of Reptiles and Batrachiam as Distinct Classes or Subclasses. —In the chronological order which we have adopted for these historical notes, we had to refer in their proper places to two herpetologists, Blainville and Latreille, who advocated a deeper than merely ordinal separation of Reptiles from Batrachians, and who were followed by F. S. Leuckart. But this view only now began to find more general acceptance. J. Müller and Stannius were guided in their classification entirely by anatomical characters, and consequently recognized the wide gap which separates the Batrachians from the Reptiles; yet they considered them merely as subclasses of the class Amphibia. The former directed his attention particularly to those forms which seemed to occupy an intermediate position between Lacertilians and Ophidians, and definitely relegated Anguis, Pseudopus , Acontias to the former, and Typhlops, Rhinophis, Tortrix, but also the Amphisbaenoids to the latter. Stannius interpreted the characteristics of the Amphisbaenoids differently, as will be seen from the following abstract of his classification : —

Subclassis : AMPHIBIA MONOPNOA (Leuckart).

Sect. 1. STREPTOSTYLICA (Stann. ). Quadrate bone articulated to the skull; copulatory organs paired, placed outside the cloacal cavity.

Ordo 1. OPHIDIA.

Subordo 1. Eurystomata or Macrostomata (Müll. ). The facial bones are loosely connected to admit of great extension of the wide mouth.

Subordo 2 . Angiostomata or Microstomata (Müll. ). Mouth narrow, not extensile; quadrate bone attached to the skull and not to a mastoid.

Ordo 2. SAURIA.

Subordo 1. Amphisibaenoidea.

Subordo 2. Kionocrania (Stann. ) = Lizards.

Subordo 3. Chamaeleonidea. Sect. 2. MONIMOSTYLICA (Stann. ). Quadrate bone suturally united with the skull; copulatory organ simple, placed within the cloaca.

Ordo 1. CHELONIA.

Ordo 2. CROCODILIA.

This classification received the addition of a fifth Reptilian order which with many Lacertilian characters combined important Crocodilian affinities, and in certain other respects differed from both, viz., the New Zealand Hatteria, which by its first describers had been placed to the Agamoid Lizards. Günther, who pointed out the characteristics of this Reptile, considered it to be coordinate with the other four orders of Reptiles, and characterizes it thus: —

Rhynchocephalia. —Quadrate bone suturally and immovably united with the skull and pterygoid; columella present. Rami of the mandible united as in Lacertilians. Temporal region with two horizontal bars. Vertebrae amphicoelian. Copulatory organs none.

5. Period of the Recognition of a Class of Reptilia as part of the Sauropsida. —Although so far the discovery of every new morphological and developmental fact had prepared naturalists for a class separation of Reptiles and Batrachians, it was left to T. H. Huxley to demonstrate, not merely that the weight of facts demanded such a class separation, but that the Reptiles hold the same relation to Birds as the Batrachians to Fishes. In his Hunterian Lectures (1863) he divided the vertebrates into Mammals, Sauroids, and Ichthyoids, subsequently substituting for the last two the terms Sauropsida and Ichthyopsida. The

Sauropsida contain the two classes of Birds and Reptiles, the Icluhyopsida those of Batrachians and Fishes. The position thus assigned to Reptiles in the system is now adopted by the majority of zoologists.

R. Owen, while fully appreciating the value of the osteological characters on which Huxley based his division, yet admitted into his consideration those taken from the organs of circulation and respiration, and reverted to Latreille’s division of warm-and cold-blooded (haematothermal and haematocryal) vertebrates, thus approximating the Batrachians to Reptiles, and separating them from Birds. He says —

“Although the Arcs and Mammalia agree as hot-blooded vertebrates in their higher cerebral development and in the more complex heart and lungs, Birds, by genetic and developmental characters as well as by the general plan of their organization, are more intimately and naturally allied to the Oviparous Saurian s than to the Viviparous Mammals. In their generation and development modern Batrachians differ from other cold-blooded air-breathers, and agree with Fishes. Present knowledge of extinct forms more clearly exposes the artificial nature of the primary groups of the oviparous vertebrates. An important link, the Ptcrosauria, or Flying Reptiles, with wings and air-sacs, more closely connecting Birds with the actual remnant of the Reptilian class, has passed away. Other extinct orders (Ganoeephala and Labyrintliodontia) have demonstrated the artificial nature of the distinction between Fishes and Reptiles, and the close transitions that connect together ail the cold-blooded Vertebrates.”

The Reptiles (or Monopnoa , Leuck.), then, form the highest of the five sub-classes into which, after several previous classifications, Owen finally divides the Hxmatocrya. The sub-class is composed of the following nine orders :—

a. Ichtiiyo pterygia (extinct)—Ichthyosaurus.

b. Sauropterygia (extinct)— Plesiosaurus, Pliosaurus, Notho- saurus, Placodus. c. Anomodontia (extinct) — Dicynodon, llhynchosaurus, Oudcn- odon. d. Chelonia.

e. Lacertilia (with the extinct Mosasaurus).

f. Ophidia.

g. Crocodilia (with the extinct Teleosaurus and Streptospon-

dylus). h. Dinosauria (extinct) — Iguanodon, Scelidosaurus, and Megalo· saurus. i. Pterosauria (extinct) — JDimorphodon, Rhamphorhynchus, and Ptcrodactylus.

As this ordinal arrangement deals in a uniform measure with extinct as well as living Reptiles, it is more complete than, and marks as great a progress in the history of herpetology as, any of the classifications recorded hitherto.

The study of fossil Reptiles had been continued after Cuvier by many workers, as Goldfuss, E. Geoffroy St Hilaire, Harlan, Mantell, G. F. Jäger, Phillips, Leidy, Falconer, Cautley, Alton, Bronn, Kaup, Quenstedt, and especially H. von Meyer, who devoted the whole of his extra-official time to drawing with his own hand numerous treasures preserved in Continental collections. But none contributed more to the knowledge of fossil Reptiles than Owen himself. Indefatigable in collecting materials, and able to bring to bear upon the subject an unsurpassed knowledge ranging over the whole field of comparative anatomy, he was unrivalled in elucidating the affinities of fossil remains as well as in the production of graphic descriptions. He showed that the number of living Reptilian types bears but a small proportion to that of extinct forms, and, therefore, that a systematic arrangement of the entire class must be chiefly based upon dental and osteological characters.

In this he was followed by Huxley and CorE who, however, have restricted still more the selection of classi-ficatory characters by relying for the purposes of arrangement on a few parts of the skeleton only. This is a matter of necessity in dealing with fossil remains, but a tendency has thereby been fostered in our times of applying the same principles in the subdivision of living Reptiles to the greater or less exclusion of the consideration of other parts of their organization.

Huxley and Cope attempted a further grouping of the orders which in Owen’s system were merely serially enumerated as cosubordinate groups. Huxley used for 1 this purpose almost exclusively the position and character of the rib-articulations to the vertebral centre, the orders themselves being the same as in Owen’s system :—

A. PLEUR.OSPONDYLIA. Dorsal vertebrae devoid of transverse processes and not movable upon one another, nor are the ribs movable upon the vertebrae. A plastron. Order 1, Chelonia.

B. The dorsal vertebrae (which have either complete or rudiment ary transverse processes) are movable upon one another, and the ribs upon them. No plastron.

a. The dorsal vertebrae have transverse processes which are either entire or very imperfectly divided into terminal facets (Erpetospoxdylia).

a. Transverse processes long; limbs, well developed, paddles; sternum and sternal ribs absent or rudimentary. Order 2, Flesiosauria (= Sauropterygia, Ow.).

p. Transverse processes short.

aa. A pectoral arch and urinary bladder. Order 3, Lacertilia. bb. No pectoral arch and no urinary bladder. Order 4, Opiiidia. ־ b. The dorsal vertebrae have double tubercles in place of trans verse processes (Perospondylia). Limbs paddle-sliaped.

Order 5, Ichthyosauria ( = Ichthyoptcrygia, Ow.).

c. The anterior dorsal vertebrae have elongated and divided transverse processes, the tubercular being longer than the capitular division (Suchospondylia).

a. Only two vertebrae in the sacrum. Order 6, Crocodilia.

p. More than two vertebrae in the sacrum.

aa. Manus without a prolonged ulnar digit.

aa. Hind-limb Saurian. Order 7, Dicynodon-tia ( = Anomodontia, Ow.).

PP. Hind-limb Ornithic. Order 8, Ornitho-scelida ( — Dinosauria, Ow.). bb. Manus with an extremely long ulnar digit. Order 9, Pterosauria.

Finally, Cope, by combining the modifications of the quadrate and supporting bones with the characters used by Huxley further developed Owen’s classification, separating the Pythonomorpha and Rhynchocephalia as distinct orders from the Lacertilia. Whenever practicable he was guided in his nomenclature by priority. The following is an abstract of his classification :—

I. Extremities beyond proximal segment not differentiated to form.

Order 1. Iciithyopterygia (Ow.).

II. Extremities differentiated.

A. Streptostylica(Stann.).

Order 2. Lacertilia.

Order 3. Pythonomorpha (Cope).

Order 4. Opiiidia.

B. Synaptosauria(Cope).

Order 5. Rhynchocephalia (Gtln־.).

Order 6. Testudinata.

Order 7. Sauropterygia (Ow.).

C. Archosauria(Cope).

Order 8. Anomodontia (Ow.).

Order 9. Dinosauria (Ow.).

Order 10. Crocodilia (Ow.).

Order 11. Ornitiiosauria (Fitz.).

The most recent general work on Reptiles is from the pen of Dr C. K. Hoffmann, and appears since the year 1879 in Brown’s Klassen und Ordnungen des Thierreichs. The author treats with predilection the parts which relate to the anatomy of Reptiles, and which will prove to be of the greatest help to the student; each chapter is preceded by a list of the most important publications. The systematic part is composed with less critical discernment, and its usefulness for scientific purposes will scarcely be commensurate with the amount of labour bestowed on its compilation.

b. Special Systematic Works.

After having followed the general history of herpetology to the present period, we have to mention the works by which our knowledge of certain orders or of the various Reptilian faunas has been specially advanced.

Crocodilia and Lacertilia. —We have already shown that the animals of these two orders were by the earlier authors thrown together in one group, of which a natural subdivision into families was attempted by Oppel and Cuvier, that Merrem (1820) was the first to recognize in the Crocodiles a separate group for which he proposed the name of Loricata, being followed therein by Blainville, who named the group Emydo-sauriens, and that Latreille actually recognized their affinities to the Chelonians, uniting them under the name of Cataphracta. In Wagler’s and Fitzinger’s systems a distinct advance is manifested by the employment of the tongue and also of the dentition as important characters. These, combined with the scutellation, the form of the toes, and the entire habitus, were also the characters on which the subsequent classifications by Wiegmann, Dumeril and Bibron, Gray, and Stannius were based, the classifications varying according to the manner in which those characters are subordinated to one another. But, while the German and English herpetologists assign to the Amphisbsenians, Chamoeleons, and Crocodiles a rank more or less above, and distant from, the Lacertilian families, Dumeril and Bibron take a singularly retrograde step in dividing Lizards into eight equivalent families, of which the first comprises the Crocodiles, and the second the Chanrue-leons, the Amphisbsenians forming part of the family Chalcididae. Gray was the last who dared to place the narrow-mouthed Snakes such as Typhlops and Rhinophis among Lizai’ds.

In the two most recent classifications of the families of Lizards osteological (or rather craniological) characters supersede almost entirely those previously employed. Cope, wdio had led the way in this direction, still allows subordinal value to the dentition as well as to the form of the tongue, as may be seen from the following scheme:—

Suborder 1. Rhiptoglossa.

Fain. 1. Chamxleontidx.

Suborder 2. Pachyglossa.

Fam. 2. Agamidx.

Suborder 3. Nyctisaura.

Fam. 3. Gccconidx.

Suborder 4. Pleurodonta. a. Iguania.

Fam. 4, A nolidx ; 5, Iguanidx. b. Diploglossa.

Fam. 6, Anguidx ; 7, Gerrhonotidx ; 8, Xcnosauridx ; 9, Ilclodcrrnidx. c. Thecaglossa.

Fam. 10. Varanidx. d. Leptoglossa.

Fam. 11, Teiidx ; 12, Lacertidx ; 13, Zonuridx ; 14, Chal-cididx ; 15, Scincidx; 16, Sepsidx. e. Typhlophthalnii.

Fam. 17, Anelytropidx ; 18, Acontiidx ; 19, Aniellid¿e.

Suborder 5. Ophiosauri.

Fam. 20, Amphisbxnidx ; 21, Trogonophidx.

Finally, whilst adopting in principle Cope’s classification, G. A. Boulenger, partly by extending his examination on types not seen by Cope, partly by differently valuing the various craniological characters, introduced considerable modifications:—

Suborder 1. Lacertilia vera.

A. Tongue smooth or with villose papillae; clavicle dilated, loop-shaped proximally; no postorbital or postfronto-

sqtiamosal arches.

Fam. 1, Geckonidx ; 2, Eublcpliaridx.

B. Tongue smooth or with villose papillae; clavicle not dilated proximally.

Fam. 3, Uroplatidx ; 4, Pygopodidx ; 5, Agamidx ; 6, Iguanidx ; 7, Xcnosauridx; 8, Zonuridx ; 9, Anguidx; 10, Aniellidx ; 11, Ileloderrnatidx ; 12, Varanidx.

C. Tongue covered with imbricate, scale-like papillae or with oblique plicae; clavicle dilated proximally, frequently loop-shaped.

Fam. 13, Xantusiidx ; 14, Tciidx; 15, Amphisbxnidx ; 16, Lacertidx, 17, Gerrhosauridx ; 18, Scincidx; 19, Anelytropidx ; 20, Dibamidx.

Suborder 2. Rhiptoglossa.

Fam. 21. Chamxleontidx.

The principal works to be consulted by the student of recent Crocodilians are the following :—

Cuvier, Ossemens fossiles, vol. v. part 2 (1824); Geoffroy St Hilaire, “Descriptions des Crocodiles du Nil,” in Mém. deVInstitut d'Égypte (1813); Dumeril and Bibron, Erpétologie générale, Paris, 8vo, vols. ii., iii. (1835-36); Huxley, “On the dermal armour of Jacare and Caiman, with notes on the generic and specific characters of recent Crocodilia,” in Jour. Proc. Linn. Soc., Zoology, vol. iv. pp. 1-28 (1860); Brühl, Das Skelett der Krokodiliner, dargestellt in 20 Tafeln (1862); Strauch, “Synopsis der gegenwärtig lebenden Crocodiliden,” in Mém. Acad. St Pétersburg, vol. x. (1866); Rathke, Untersuchungen über die Entwickelung und den Körperbau der Crocodile, Brunswick, 4to (1866); Gray, Catalogue of Shield-Reptiles in the Collection of the British Museum,—part ii., Emydo-saurians, lihynchoceplialia, and Amphisbsenians, London, 4to (1872); Parker, On the Structure and Development of the Sktill in the Crocodiles, London, 4to (1883).

The principal special works to be consulted by the student of recent Lacertilians are the following :—

Wiegmann, Hcrpetologia mexicana,—Pars 1, Saurorum species amplectens, Berlin, fol. (1834); Dumeril and Bibron, Erpétologie générale, Paris, 8vo, vols. 2-5 (1836-39); Gray, Catalogue of the Specimens of Lizards in tlx Collection of the British Museum, London, 16mo (1845); Brücke, Beiträge zur vergleichenden Anatomie und Physiologie des Gefäss-Systems der Amphibien, Vienna, 4to (1852); Rathke, Ucbcr den Bau und die Entwicklung des Brustbeins der Saurier (1854); Fritsch, Zur vergleichenden Anatomie des Amphibien-Herzens, Berlin, 8vo (1869); Fürbringer, Die Knochen icnd Muskeln der Extremitäten bei den schlangenähnlichen Sauriern, Leipsie, 4to (1870); Braun, Das Urogenitalsystem der einheimischen Reptilien, Würzburg, 8vo (1877); Parker, On the Structure and Development of the Skull in the Lacertilia, (1879); Boulenger, Catalogue of the Lizards in the British Museum, 2d edition, London, 8vo (vol. i. in progress, 1885).

In a short sketch like the present it would be impossible to refer even to a small part only of the immense number of contributions by ־which our knowledge of Lizards has been advanced within the last forty years, either by adding to that of species previously imperfectly known, or by describing new generic and specific forms. But an idea of this increase may be formed by a comparison of Gray’s and Boulenger’s catalogues; whilst the former enumerated 186 species out of the families Geckonidx and Agamidx, Boulenger describes not less than 490 belonging to the same groups.

Ophidia. —We have already mentioned that in Oppel’s system (1811) the first step is taken towards a natural classification of Snakes. Neither C. Duméril nor Merrem, Fitzinger nor Wagler, indicated the way towards a more natural arrangement; it seemed almost as if with the increase of the number of distinct genera their arrangement became more and more hopeless. In the meantime the Rijks Museum of Leyden had enriched itself under the able direction of Temminck, through the efforts of traveller-naturalists like Reinwardt, Kuhl, Van Hasselt, Boie, and Siebold from the Dutch colonies in the East and West Indies, with materials fairly rivalling those accumulated in Paris. They were at first studied by the brothers Friederich Boie and Heinrich Boie, who well characterized a number of genera but failed in the attempt to arrange them in a natural or logical system. All the more remarkable, therefore, is the production by H. Schlegel of an Essai surla Physionomie des Serpens (Leyden, 1837; 2 vols. 8vo, with atlas in fol.). In this classical work the whole of the subject is treated throughout in a scientific manner; the species are described with a clear discernment of really distinctive characters, the description being generally accompanied with a faithful outline figure of the head, and with a critical examination of the literature. Schlegel, besides, has the merit of having recognized the great importance of exactness with regard to localities, and of giving a general account of the geographical distribution of Snakes. The principle of classification adopted by Schlegel, indeed, is not one which will be recognized as final or even as legitimate at the present time, but it is one which is preferable to that employed by Müller, Duméril, and Bibron, which led, as we shall see presently, to the most artificial grouping of species. He divided the Snakes into families according to their “physiognomy,” that is “l'impression totale que fait sur nous l’ensemble d’un être quelconque, impression que l'on peut sentir, mais qu’il est impossible de rendre au moyen de paroles; elle est le résultat de l’harmonie de toutes les parties isolées, dont on embrasse la confirmation d’un coup d’oeil, et dans leurs rapports mutuels.” Schlegel had no training in, or knowledge of, anatomy; he, therefore, ignored Müller’s researches which appeared a few years before his work; yet it is noteworthy that his classification stands in the main, and has not yet been superseded. He divides Snakes as follows :—

I. Non-venomous Snakes.

Fam. 1. Burrowing.

Gen. Tortrix.

Fam. 2. Worm-like.

Gen. Calamaria.

Fam. 3. Terrestrial.

Gen. Coronella, Xenodon, Heterodon, Lycodon, Coluber, Herpetodryas, Psammophis.

Fam. 4. Arboreal.

Gen. Dendrophis, Dryophis, Divisas.

Fam. 5. Freshwater.

Gen. Tropidonotus, Homalopsis.

Fam. 6. Boas.

Gen. Boa, Python, Acrochordus.

II. Venomous Snakes.

Fam. 7. Colubriform.

Gen. Εlaps, Bungamis, Naja.

Fam. 8. Marine.

Gen. Hydrophis.

Fam. 9. Venomous Snakes proper.

Gen. Trigonocephalus, Crotalus, Vipera.

Already in 1832 J. Müller had proposed “a natural classification of Snakes on anatomical principles,” in which he paid particular attention to the osteology of the hitherto dubious forms of Ophidians, but in the end based his arrangement entirely on the structure of the jaws and on the dentition. As he did not extend his examination into other parts of the organization of the various genera, it may suffice here to state that he divided all Snakes into two sections, the first of which (Ophidia microstomata) comprised the four families Amphisbaenoidea, Typhlopina, Uropeltacea, and Tortricina, and the second (Ophidia macrostomata) all the other Snakes, which he referred to seven families.

The direction thus indicated by Müller was followed by Dumeril and Bibron, who, however, by their much more detailed knowledge of Snakes, were enabled to subdivide the unwieldy categories formed by Müller; also the genera which in Schlegel's system comprised Snakes with very different dentition had to be subdivided, and were defined with greater precision than had been done by any previous herpetologist. They divide Snakes into five equivalent sections :—

1. Opotérodontes. Teeth in one of .the jaws only: 2 families and 8 genera.

2. Aglyphodontes. Teeth in both jaws, none grooved: 12 families and 86 genera.

3. Opisthoglyphes. Posterior maxillary teeth grooved: 6 families and 37 genera.

4. ProtéRogLYPHES. Anterior maxillary tooth grooved and fol lowed by other smooth teeth: 2 families and 16 genera.

5. Solénoglyphes. Anterior maxillary teeth perforated and iso lated: 2 families and 13 genera.

The progress made in ophiology from the time of the appearance of this work down to the present period consists rather in the increase of our knowledge of the great variety of species and genera than in the further development of the system. Gray, Reinhardt, Peters, Günther, Cope, Bocage, Jan, Krefft, and others described a large number of forms, so that the number of those known to Duméril and Bibron has now been perhaps trebled or quadrupled. Unfortunately, no general work corresponding to the present state of science exists. But two works published subsequently to the Erpétologie générale are indispensable to the student.

The first is the Catalogue of the Specimens of Snakes in the Collection of the British Museum, of which the first part, containing the Viperine Snakes, Water-Snakes, and Boas, by J. E. Gray, appeared in 1849, and the second, containing the Colubrines, by A. Günther in 1858. The classification, which was much behind its time, was fixed by the former of the two authors, so that the latter had to accommodate the arrangement of his part to that of his predecessor. However, he strongly opposed the application of the character of grooved posterior teeth to the formation of large sections, and generally adopted the principle advocated by Schlegel, whose generic groups were raised into families. A great number of Snakes unknown to Duméril are described in these catalogues, whilst others which happened not to be represented in the British Museum are omitted.

G. Jan in his Elenco Sistematico degli Ofidi descritti e disegnati per l'Iconografia generale (Milan, 1863, 8vo) generally adopts the families created by Günther, but institutes under each two divisions, Aglyphodonta and Glyphodonta. Jan’s great merit is the publication of his Iconographie générale des Ophidiens (Milan, 1860-76 ), in which he figures all species which were in the Milan Museum or lent to him by other institutions, and which thus forms an invaluable aid in the determination of species. The author died during the progress of the work, but it was continued by his artist, Sordelli. No descriptive letter-press worthy of the name accompanies this work.

The anatomy of Ophidians has hitherto received less attention than that of the other Reptilian orders. Besides the information contained in general works, we refer here only to two important special treatises :—

Ratlike, Entwicklungsgeschichte der Natter, Königsberg, 1839, 4to; and Parker, On the Structure and Development of the Skull in the Common Snake (Tropidonotus natrix), London, 1879, 4to.

Chelonians.— Of ante-Cuvierian authors who paid special attention to this suborder the following deserve special mention :—J. G. Walbaum, J. G. Schneider, J. D. Schoepf, and A. F. Schweigger. Five or six

4to (left incomplete by the death of the author).

distinct types of Chelonians were soon recognized, and appear also in Cuvier’s Règne Animal, viz., Testudo, Emys, Chelys, Trionyx, Chelonia with Sphargis. These types were at first recognized as genera, and raised by the subsequent authors to the rank of families, in which many more genera were distinguished, the arrangements merely differing in the various methods of subordination of the different families.

The anatomy of Tortoises was investigated chiefly by C. Perrault, who gave a detailed description of one of the Gigantic Land Tortoises in Mem. Ac. Sc. Paris, iii. (1666-69); by Cuvier in the Ossemens fossiles; by Wiedemann in Arch. f. Zool. und Zoot, 1802; by Geoffroy St Hilaire in Ann. Mus., xiv.; and especially by L. H. Bojanus, who published an anatomical monograph of Emys europaea, in which all parts are illustrated in detail, the plates being accompanied by an explanatory text. H. Rathke studied their development, and L. Agassiz and W. K. Parker that of the Turtles.

The most complete systematic and descriptive work is that by J. E. Gray. He engaged in the study of Tortoises at various times, subdividing the principal groups, as the materials grew under his hands, at first principally on the ground of external characters, and afterwards of such Craniological features as seemed to him of generic value. Alexander Strauch contributed two painstaking memoirs, the second of which is especially valuable as it contains a collection of all the published facts concerning the distribution of Tortoises over the globe. The authors mentioned associated Sphargis with Chelonia, the later ones generally as the type of a distinct family, all the marine Turtles being comprised in a section Pinnata or Euereta (Stannius); and it was only Cope who recognized in the want of specialization of the skeleton of the Leathery Turtle sufficient grounds for separating it into a distinct section, Athecae. c. Faunistic Works.

In noticing the principal faunistic works, we omit the majority of the older and antiquated publications, and almost all treatises which appeared in periodicals, as their existence can be readily ascertained by reference to works of more modern date or of a more general scope.

Europe.—(1) T. Bell, A History of British Reptiles; 2d ed., London, 1849, 8vo. (2) S. Nilsson, Scandinavisk Fauna,, pt. iii.; Amfibierne, 2d ed., London, 1860, 8vo. (3) A. Strauch, “Die Schlangen des Russischen Reichs,” Mém. Ac. Se. St Rétersburg, xxi. 1873, 4to. (4) H. Schlegel, De Dieren van Nederland: Kruipende Dieren, Haarlem, 1862, 8vo. (5) F. Leydig, Die in Deutschland lebenden Arten der Saurier, Tübingen, 1872, 4to; and Ueber die einheimischen Schlangen, Frankfort, 1883, 8vo. (6) E. Schreiber, Herpetologia Europaea, Brunswick, 1875, 8vo. (7) V. Fatio, Faune des Vertèbres de la Suisse, vol. iii. of Hist. nat. des Reptiles et des Batraciens, Geneva, 1872, 8vo. (8) C. L. Bonaparte, Iconografia della Fauna italien, νol. ii., "Amfibi,” Rome, 1832-41, fol. (9) E. de Betta, Erpetologia delle provincie Venete e del Tirolo meridionale, Verona, 1857, 8vo. (10) A. Strauch,Essai d’une Erpétologie de l’Algérie,” Mém. Acad. Sci. St Pétersburg, 1862, 4to. (11) F. Lataste, Essai d'une Faune Herpétologique de la Gironde, Bordeaux, 1876, 8vo. (12) J. von Bedriaga, Die Amphibien und Reptilien Griechenlands, Moscow, 1882, 8vo.

Persia.—W. T. Blanford, Eastern Persia, vol. ii., London, 1876, 8vo.

Catalogue, Ac., 1872.

and 1865.

kröten über den Erdball,” in Mémoires de l'Acad, de St Petersb., 1862

Japan.—H. Schlegel, Fauna Japonica—Reptiles, Leyden, fol.

East Indies.—(1) P. Russel, Account of Indian Serpents, collected on the coast of Coromandel, containing Descriptions and Drawings of each Species, London, 1796, fol., and A Continuation of an Account of Indian Serpents, London, 1801-3, fol. (2) H. Schlegel, Abbildungen neuer oder unvollständig bekannter Amphibien, Düsseldorf, 1837-44, text 8vo, atlas fol. (3) J. E. Gray and Hardwicke, Illustrations of Indian Zoology, London, 1830-32, fol. (4) T. Cantor, Catalogue of Reptiles inhabiting the Malayan Peninsula and Islands, Calcutta, 1847, 8vo. (5) A. Gunther, Reptiles of British India, London, 1864, fol. (6) W. Theobald, Catalogue of the Reptiles of British India, Calcutta, 1876, 8vo. (7) J. Fayrer, The Thanatophidia of India, London, 1874, fol. (8) J. Anderson, Anatomical and Zoological Researches, comprising an account of the Zoological Results of the two Expeditions to Western Yunnan, London, 1878, 4to.

Africa.—(1) Description de IEgypte—Histoire naturelle—Reptiles, Paris, fol., 1809, &c. (2) A. Smith, Hhistrations of the Zoology of

South Africa, London, 8vo, 1849. (3) W. Peters, Naturwissen schaftliche Reise nach Mossambique—Zoologie, iii., “Amphibien,” Berlin, 1882, 4to.

North America.—(1) R. Harlan, American Herpetology, or Genera of the North American Reptilia, with a Synopsis of the Species, Philadelphia, 1827, 8vo. (2) J. E. Holbrook, North American Herpetology, or a Description of the Reptiles inhabiting the United States, 5 vols., with numerous col. plates, Philadelphia, 1836-43, 4to. (3) D. H. Storer, “Report on the Reptiles of Massachusetts,” in Boston Jour. Nat. Hist., iii., 1841, pp. 1-65. (4) J. E. De Kay, Zoology of New York, vol. iii., “Reptiles and Amphibia,” Albany, 1842, 4to. (5) S. F. Baird and S. Girard, Catalogue of North American Reptiles in the Museum of the Smithsonian Institution, pt. i. “Serpents,” Washington, 1853, 8vo. (6) Id., Reports upon Reptiles in Reports of Explorations for a Railroad from the Mississippi to the Pacific Ocean, Washington, 1859, 4to. (7) L. Agassiz, Contributions to the Natural History of the United States of America, vol. ii., “North American Teshidisiata,'' Boston, 1857, 4to. (8) S. Garman, “On the Reptiles and Batrachians,” Mem. Mus. Comp. Zool., Cambridge, 1883, 4to. (9) H. C. Yarrow, Check-List of the North American Reptiles and Batrachians, with Catalogue of the Specimens in the U. S. National Museum, Washington, 1883, 8vo. (10) E. D. Cope is the author of numerous memoirs and papers in the various North American periodicals.

Tropical America. —(1) Prince Maximilian von Wied, Abbildungen zur Naturgeschichte Brasiliesis, Weimar, 1822-31, fol., and Beiträge zur Naturgeschichte von Brasilien, i. “Amphibien,” Weimar, 1825, 8vo. (2) J. B. Spix, Serpesitum Brasiliesisium species novae, Munich, 1824, fol.; Id., Ranae et Testudinis Brasiliensis species siovae, Munich, 1825, fol.; Id., Asiimalia siova sive species novae Lacertarum quas in itinere per Brasiliam ansiis 1817-20, jussu et auspiciis Maxisniliani Josephi I., Bavariae regis, suscepto collegit et deseripsit, &c., Munich, 1825, fol. (3) A. F. A. Wiegmann, Herpeto-logia mexicasιa, pars i., Saurorum species amplectens, Berlin, 1834, fol. (4) J. J. v. Tschudi, Untersuchungen über die Faunaperuasia auf eisier Reise in Peru während der Jahre 1838-42, St Gall, 1846, fol. (5) Guichenot, in C. Gay’s Historia fisica y politica de Chile, ii., “Reptiles,” Paris, 1848, 8vo, atlas fol. (6) Cocteau and Bibron, in Ramon de la Sagra’s Histoire physique, politique, et naturelle de l'ile de Cuba—Reptiles, Paris, text 8vo, atlas fol. (7) F. de Castelnau’s Expédition dans les parties centrales de l'Amérique du Sud—Zoologie—Reptiles, by A. Guichenot, Paris, 1855, 4to. (8) C. Girard, Reptiles (from Chili) in U. S. Naval Astronomical Expedition to the Southern Hesnisphere, vol. ii., Washington, 1855, 4to. (9) S. F. Baird, U. S. Exploring Expedition, vol. xx., “Herpetology,” Philadelphia, 1858, atlas fol. (10) Duméril and Bocourt, Mission scientifique au Mexique et dans l'Amérique Centrale—Études sur les Reptiles et les Batraeiesis, Paris, 1870, 4to (in progress). (11) A. Günther, in Salvin and Godman’s Biologia Centrali-Americana— Reptiles, London, 1885, 4to (in progress). (12) E. D. Cope, numerous papers in the various North American periodicals.

Australia.—(1) J. E. Gray and A. Günther treat of the Lizards in Zoology of the Voyage of H.M.S. “Erebus” and “Terror," London, 1844, 1875, 4to. (2) G. Krefft, The Snakes of Australia, Sydney, 1869, 4to. (3) W. Peters and J. Doria, in Ann. Mus. Genov., xiii., 1878, 8vo.

General Characters of the Class Reptiliα.

Reptiles are vertebrate animals, the skin of which is covered with horny or bony plates (scales or scutes). The heart has two auricles, but with the ventricular chamber generally incompletely divided; two arterial trunks emerge from the right portion of the ventricle; the blood of the arterial and venous systems mixes either in the heart or at the origin of the aortic arches. Respiration takes place by lungs, never by bronchiae; portions of the lungs are simple without minute subdivision of the cavity; and the respira-

Supplement to the Catalogue, Ac., 1870, and by Appendix to the tory movements are slow and irregular. In consequence, Reptiles are cold-blooded animals. Their blood-corpuscles are red and nucleated. The thoracic and abdominal viscera are never separated by a complete diaphragm. The intestinal tract and the urogenital organs open into a common cloaca; the oviducts are developed from the Müllerian ducts, and dilated in their lower course for the reception of the ova; all Reptiles are oviparous or ovoviviparous.

The vertebral column articulates with the skull almost invariably by means of a single convex occipital condyle. The mandible consists of several distinct pieces, of which the articular bone articulates with a quadrate bone, interposed between skull and mandible. When the appendicular parts of the skeleton are present, the sternum is never replaced by membrane bone, and the posterior sternal ribs are attached to a median prolongation of the sternum. The ilia are prolonged farther behind the acetabulum than in front of it; the pubic bones directed downward and forward, and, like the ischia, forming a median symphysis. The metatarsal bones are not anchylosed among themselves or with the distal tarsal bones.

As in Birds and Mammals, the foetus of Reptiles is enclosed in an amnion and allantois (Amniota), and nourished from the vitellus of the egg.

In some of the most important characters mentioned above Reptiles agree with Birds, as in the presence of a single occipital condyle, a complex lower jaw articulated to the skull by a quadrate bone, and nucleated blood-corpuscles. The majority of naturalists, therefore, consider the two classes to constitute one of the main divisions of Vertebrates, the Sauropsida. At the present epoch, indeed, Birds are strikingly differentiated from Reptiles, but the discoveries within recent years of a number of extinct Birds with Reptilian characters offer ample evidence that Birds are the descendants of some branch or branches of the Reptilian type, in which the power of flight was developed, and with it other anatomical peculiarities by which Birds are now distinguished from living Reptiles.

plates. A pair of clavicles rest upon an interclavicle and pass laterally to the scapulae; a pair of broad not overlapping coracoids form the posterior part of the pectoral arch. A sternum is replaced by a series of abdominal splints.

Fam. a. Sauranodontidae. Edentulous. Genus: Sauranodon, from the Jurassic formations of the Eocky Mountain region.

Fam. b. Ichthyosauridae. Teeth numerous, implanted in a common alveolar groove. Genus: Ichthyosaurus, from Mesozoic strata up to the Chalk.

Order 2. Axomodontia (extinct). Lacertiform Reptiles, the skull and four limbs of which are Lacertilian in most of their characters. Vertebrae biconcave, four or five of them anchylosed together and forming a sacrum. The tubercular and capitular articulations are separated, the former and longer being on the diapophysis, the latter and shorter on the centrum; ribs movable, the anterior with a bifurcate head. Os quadratum suturally connected with the skull. A foramen parietale is present. Jaws Chelonian and probably cased in horny sheaths; either The division of Reptilia into Orders.

Of the various modifications that have been proposed in the classification of Reptiles the more important are mentioned in the historical part of this article. We adopt here a serial arrangement of those orders which seem to be well established, having already referred to the attempts that have been made to arrange these orders into higher groups.

Order 1. Ichtiiyopterygia (extinct). Marine Reptiles with a Cetacean-like naked body and with four limbs formed into paddles, the parts of which after the humerus are not differentiated as to form or function. Tail long. Vertebrce numerous, biconcave; no sacrum. Dorsal vertebrae with double tubercles; ribs movable, the anterior with bifurcate heads. Head large, with long powerful snout, joined to the trunk without neck. Quadrate bone immovably articulated to squamosal. A foramen parietale is present. Orbits very large with a circle of sclerotic edentulous or each maxillary bone was armed with a long evergrowing tusk, which sometimes was accompanied by other smaller teeth. The pectoral arch consisted of scapula and coracoid, but a clavicle seems to have been absent. Pelvis very strong, with continuous ischio-pubic symphysis.

Genera: Dicynodon, Galesaurus.

Order 3. Dinosauria (extinct). This comprises Reptiles of a great diversity of form and size, some adapted for a terrestrial, others for an aquatic life, some carnivorous, the majority herbivorous, but all distinguished by characters leading more or less closely from the Reptilian up to the Avian type. The majority of trunk vertebrae have fiat or slightly concave articular ends, sometimes a few of the anterior are convex in front; cervical vertebrae numerous; a sacrum is formed by more than two coalesced vertebrae. Neural arches united to the centra by sutures. Thoracic ribs movable, with a bifurcate head; cervical ribs united to the vertebrae either by suture or anchylosed.

Os quadratum suturally connected with the skull. The premaxillary bones are separate, and the rami of the lower jaw united in front by cartilage only. Form of the teeth variable; they are not anchylosed to the bone. Two pairs of limbs are present, of which the hinder pair is the longer and larger, and generally ambulatory. The structure of the pelvis and hind limbs partly Ornithic; the pelvic bones are not coalesced with each other or with the sacrum; the pubis enters into the formation of the acetabulum, and the ilium is prolonged forwards in front of the acetabulum; ischia united in a median ventral symphysis. The head of the femur is placed at a right angle to the condyles; tibia with a procnemial crest, and a ridge for the fibula, which is complete. The proximal row of tarsals is formed by the astragalus and calcanéum only, and the former sometimes anchylosed with the tibia, thus forming the upper portion of the ankle-joint. In the case of no other group of Reptiles has knowledge, within the last few years, advanced so much as in that of Diuosaurians. It has supplied, on the part of the Reptilian type, the remarkable forms by which the chasm between living Birds and Reptiles is bridged over. Huxley’s interpretation as to the affinities of these fossils, which was at first based on very imperfect materials, but on sufficient evidence to lead him to substitute the name of Ornithoscelida for the older one of Dinosauria, has been fully verified by the astonishing discoveries of most perfect remains at Beruissart in Belgium and in Jurassic formations of the United States. Compared with these recent discoveries, the materials upon which Von Meyer, Owen, Leidy, Hulke, and Seeley based their researches must appear very fragmentary. The specimens found in the Wealden of Bernissart were those of different species of Iguanodon, the skeletons of which were almost complete, the bones being preserved in their natural position and connexion; they have formed the subject of a series of memoirs by L. Dollo (Bulk Mas. R. d'Hisk Nat. Belg., 1882-84). But these materials are far surpassed, as regards number and diversity of forms, by the discoveries in America, which have been made known by Cope and especially by O. C. Marsh.

All the Dinosaurian remains known at present belong to the Mesozoic age; they appear first in the Triassic, but the majority from these formations are so fragmentary that their classification is subject to much uncertainty. Some at least of the celebrated three-toed footprints which were discovered some fifty years ago in the United States, and about the origin of which much uncertainty existed, are evidently those of Dinosaurs. In the Jurassic these Reptiles attained their greatest development, Marsh distinguishing among the fossils of this period four orders with numerous families. The largest exceeded auy other land animal in size, and measured from 50 to 80 feet. Dinosaurs continued to the end of the Cretaceous period, and some genera became highly specialized, although none attained to the same large size as some of the Jurassic forms.

The disproportion in length and strength between the fore and hind limbs clearly shows that the mode of progression differed widely from that of ordinary Reptiles, and was bipedal at least in some of the genera. In assuming an erect position, their long tail assisted them in balancing the body. Some possessed a dermal armour, the scutes being sometimes produced into enormous spines; others were provided with defensive weapons in the shape of spines attached to the fore-feet. The teeth vary exceedingly: in some of the carnivorous genera they are sharp, pointed, serrated, and recurved, in others flat, in others broad and molar-like; in some the preniaxillae are toothed, in others toothless and beak-like.

Marsh compares the Dinosaurs, as regards diversity of form, with the Marsupials, and thinks that, like these latter, they should take the rank of a subclass rather than order. The following is an abstract of his latest classification of the proposed subclass Dino-sauria :—

Order 1. Sauropoda. Feet plantigrade, ungulate; five digits in manus and pes; second row of tarsals and carpals unossified. Pubes united distally by cartilage; no post-pubis. Anterior vertebrae Opisthoccelian. Presacral vertebrae hollow. Fore and hind limbs nearly equal; limb bones solid. Sternal bones paired. Premaxillaries with teeth. Anterior nares at top of the skull.—Herbivorous.

Fam. a. Atlantosauridae. Ischia directed downwards, with expanded extremities meeting on median line. Anterior caudal vertebrae with lateral cavities. Genera: Atlantosaurus, Apatosaurus, Brontosaurus. Gigantic Dinosaurians from Upper Jurassic deposits of Colorado, species of the first genus having attained to the enormous length of 80 feet. They are the least specialized forms of the subclass, and approach in some respects Mesozoic Crocodilians.

Fam. b. Diplodocidae. Ischia with a straight shaft, not expanded distally, directed downward and backward, with the ends meeting in the median line. Caudal vertebrae deeply excavated below.—One genus:

Order 4. Ornithosauria (extinct). Reptiles with the fore limb adapted to support a flying membrane, and

All the Dinosaurian remains known at present belong to the Mesozoic age; they appear first in the Triassic, but the majority from these formations are so fragmentary that their classification is subject to much uncertainty. Some at least of the celebrated three-toed footprints which were discovered some fifty years ago in the United States, and about the origin of which much uncertainty existed, are evidently those of Dinosaurs. In the Jurassic these Reptiles attained their greatest development, Marsh distinguishing among the fossils of this period four orders with numerous families. The largest exceeded atιy other land animal in size, and measured from 50 to 80 feet. Dinosaurs continued to the end of the Cretaceous period, and some genera became highly specialized, although none attained to the same large size as some of the Jurassic forms.

The disproportion in length and strength between the fore and hind limbs clearly shows that the mode of progression differed widely from that of ordinary Reptiles, and was bipedal at least in some of the genera. In assuming an erect position, their long tail assisted them in balancing the body. Some possessed a dermal armour, the scutes being sometimes produced into enormous spines; others were provided with defensive weapons in the shape of spines attached to the fore-feet. The teeth vary exceedingly: in some of the carnivorous genera they are sharp, pointed, serrated, and recurved, in others flat, in others broad and molar-like; in some the preniaxillae are toothed, in others toothless and beak-like.

Marsh compares the Dinosaurs, as regards diversity of form, with the Marsupials, and thinks that, like these latter, they should take the rank of a subclass rather than order. The following is an abstract of his latest classification of the proposed subclass Dino-sauria :—

Order 1. Sauropoda. Feet plantigrade, ungulate; five digits in manus and pes; second row of tarsals and carpals unossified. Pubes united distally by cartilage; no post-pubis. Anterior vertebrae Opisthoccelian. Presacral vertebrae hollow. Fore and hind limbs nearly equal; limb bones solid. Sternal bones paired. Premaxillaries with teeth. Anterior nares at top of the skull.—Herbivorous.

Fam. a. Atlantosauridae. Ischia directed downwards, with expanded extremities meeting on median line. Anterior caudal vertebrae with lateral cavities. Genera: Attantosaurus, Apatosaums, Brontosaurus. Gigantic Dinosaurians from Upper Jurassic deposits of Colorado, species of the first genus having attained to the enormous length of 80 feet. They are the least specialized forms of the subclass, and approach in some respects Mesozoic Crocodilians.

Fam. b. Diplodocidae. Ischia with a straight shaft, not expanded distally, directed downward and backward, with the ends meeting in the median line. Caudal vertebrae deeply excavated below.—One genus:

Diplodocus, from the same formation as the preceding, with very-weak dentition, limited to the fore part of the jaws.

Fam. c . Morosauridae. Ischia slender, with twisted shaft, directed backward, and with the sides meeting in the median line. Anterior caudal vertebrae solid. Genera, occurring in Europe as well as America: Bothriospondylus, Cetiosaurus, Chondrosteosaurus, Euca-merotus, Ornithopsis, Pelorosaurus.

Order 2. Stegosauria. Feet plantigrade, ungulate; five digits in manus and pes; second row of carpals unossified. Post-pubis present. Fore limbs very small; locomotion mainly on hind limbs. Vertebrae and limb bones solid. An osseous dermal armour.—Herbivorous.

Fam. a. Stegosauridae. Vertebrae biconcave. Ischia directed backward, with the sides meeting in the median line. Astragalus coalesced with tibia. Metatarsal short. Genera: Stegosaurus Oiypsirhophus), some 30 feet long, from the Jurassic beds of the Rocky Mountain region, well armed with enormous bucklers, some of which bore spines; Diracodon; Amosaums, from British formations (Kimme-ridge Clay).

Fam. b. Scelidosauridae. Astragalus not coalesced with tibia; metatarsals elongate. Genera European: Scelidosaurus, from the Lias; Acanthopholis, from the Chalk; Crataeomus; Hylaeosaurus, from the Wealden; and Polacanthus.

Order 3. Ornithopoda. Feet digitigrade with five functional digits in manus and three or four in pes. Post-pubis present. Vertebrae solid. Fore limbs small; hind-limbs hollow. Premaxil-Iaries edentulous in front.—Herbivorous.

Fam. a. Hadrosauridae. Several series of teeth, forming with use a tessellated grinding surface. Anterior vertebrae opisthoccelous. GeneraAmerican: Hadrosaums, Agathaumas(I), Cionodon.

Fam. b. Hypsilophodontidae. A single series of teeth. Four functional digits in pes. A single rhomboidal sternal ossification. Genus: Hypsilophodon, from the Wealden of the Isle of Wight.

Fam. c. Iguanodontidae. A single row of teeth. Three functional digits in pes. Two symmetrical sternal ossifications. Two genera from Europe: Iguanodon and Vectisaums ; and three comparatively small forms from the Dinosaurian deposits in North America: Camptonotus, Laosaums, Kanosaurus. Of these Iguanodon is the one which was first discovered (1825), and of which skeletons have been obtained as complete as we can ever hope to see of these creatures. The remains occur in formations from the Kimmeridge Clay to the Upper Greensand, and have been referred to three species, varying in size from 10 to 35 feet in length. They most probably were aquatic in their habits, using their powerful tail as a propelling organ, like the Crocodiles; but they differed from them in their mode of locomotion on shore, walking on their hind legs like a Struthious Bird. (See fig. 1.)

Order 4. Theropoda. Feet digitigrade; digits with prehensile claws. Pubes distally coalesced. Vertebrae more or less cavernous. Fore limbs very small; limb bones hollow. Premaxillaries with teeth.—Carnivorous. This order, although on the whole comprising less gigantic fossils than the preceding, includes some very large forms which are believed to have preyed upon the weaker herbivorous members of Dinosaurians.

Fam. a. Megalosauridae. Vertebrae biconcave. Pubes slender and united distally. Astragalus with ascending process. Five digits in manus and four in pes. Genera: Megalosaums (European); Allosaurus, Caelosaurus, Creosaurus, Dryptosaums (Laelaps) (American).

Fam. b. Zanclodontidae. Vertebrae biconcave. Pubes broad, elongate plates with anterior margins united. Astragalus without ascending process. Five digits in manus and pes. Genera: Zanclodon, Teratosaurus (?) from the European Trias.

Fam. c. Amphisauridae. Vertebrae biconcave. Pubes rod-like; five digits in manus and three in pes. Genera: A mphisaums (Mega-dactylus), Bathygnathus(?), Clepsysaurus(?) (American); Palaeosaurus and Thecodontosaurus, European Trias.

Fam. d. Labrosauridae. Anterior vertebrae opisthoccelous and cavernous. Metatarsals much elongated. Pubes slender, with anterior margins united. Genus: Labrosaurus, from America.

Fam. e. (or suborder) Caeluria. Bones pneumatic or hollow. Anterior cervical vertebrae opisthoccelous, the other biconcave. Metatarsals very long and slender. Genus: Coelurus, from America. Very imperfectly known; the remains indicate animals not larger than a wolf, and possibly of arboreal habits.

Fam. f. (or suborder) Compsognatha. Anterior vertebrae opisthocoelous. Three functional digits in manus and pes. Ischia with a long symphysis in the median line. One genus: Compsognathus, from Solenhofen; a small form, with long neck, lightly built head, strongly toothed jaws, small fore and very long hind limbs; its femur was shorter than the tibia.

Order 5. Hallopoda. Feet digitigrade, unguiculate; three digits in pes; metatarsals much elongate; calcanéum much produced backwards. Fore limbs very small; vertebrae and limb bones hollow; vertebrae biconcave. Genus: Hallopus. Its pertinence to the Dino-saurians is doubtful. The hind feet were adapted for leaping.

with the remainder of the skeleton secondarily modified for aerial progression. Vertebrae not numerous, precoelous; from three to six forming a sacrum; cervical vertebrae exceeding in size the others. No neuro-central suture. Anterior ribs with bifurcate heads. Skull large, bird-like, with long jaws. Os quadratum suturally connected with the skull. Orbits very large, with a ring of sclerotic plates. Sternum broad, completely ossified, with a median crest anteriorly. Scapula and coracoid slender, Bird-like; no clavicle. Phalanges of the ulnar digit exceedingly elongate. Pelvis weak; hind limb smaller than fore limb. Bones generally hollow, many with pneumatic foramina.

Fam. a. Pterosauria. Jaws toothed; scapula and coracoid separate. Genera: Pterodactylus, Rhamphorhynchus, Dimorphodon, from Jurassic formations of Europe; of small or moderate size.

Fam. b. Pteranodontia. Edentulous; scapula and coracoid solidly united, the former articulating with the common neural spine of the vertebrae. Genus: Pteranodon, from Cretaceous strata of Kansas; specimens with a spread of wing of some 20 feet.

Order 5. Ckocodilia. Reptiles with Lizard-like body, and long powerful tail adapted for swimming. Limbs short, especially the anterior; five digits in manus and four in pes; only three of the digits are clawed. A dermal armour, consisting of flattened bony scutes, covers the back, and in some genera the abdomen. Teeth in a single row, implanted in distinct sockets. Nostrils generally at present; but a system of free abdominal ribs is developed. The pectoral arch consists of a pair of large coracoids, meeting in the median line, and clavicular elements extending from one scapula to the other. Pelvis large, with the ilia, pubes, and ischia not coalesced, and all sharing in the formation of the acetabulum.

These characters may not fully apply to all the genera which have been referred to this order, as some are known from their skulls or other fragments only.

The best known are the Plesiosaurians (q.v.) proper Neusti-cosaurus, from the Trias, with paddles in front and ordinary limbs behind; gigantic forms from the Trias, as Nothosaunis, Simo-saurus, Pistosaurus, or post-Triassic, as Plesiosaurus, and Plio-saurus, Polycotylus, and Elasmosaurus (or Discosaurus) from the Liasand Chalk.

Order 7. Rhynciiocephalia. Lacertiform Reptiles, with four limbs. Vertebrae with flat ends; two in the sacrum; the tubercular and articular surfaces are united; ribs single-headed. Os quadratum suturally united with the skull and pterygoid; an osseous infra-temporal bar. Foramen parietale present. Sternum and a system of abdominal ribs well developed. Copulatory organs absent; urinary bladder present.

One recent genus: Hatteria. Represented in the Upper Cretaceous or near the end of the snout Vertebrae with the neurocentral suture persistent. Two sacral vertebrae only. The majority of the cervical and trunk ribs double-headed, attached to the diapophysis and centrum of the vertebrae. From seven to nine of the anterior dorsal ribs are united with the sternum by sternal ribs. Bones of the skull very solid, firmly united by sutures, as is also the quadrate bone. Heart with a double ventricle. Copulatory organ single, situated in the cloaca.

Fam. a. (or suborder) Procoelia. With procoelous vertebrae. All living genera and the extinct forms down to the Chalk belong to this division.

Fam. b. (or suborder) Amphicoelia. With amphiccelous vertebrae. All the genera are pre-Cretaceous: Teleosaurus, Goniopholis, Strep-tospondylus, Steganolepis, Galesaurus (?), Belodom.

Order C. Sauropterygia (extinct). Marine Reptiles with long neck, small head, long tail, natatory limbs, and a naked skin. Hind and fore limbs identical in structure and form, transformed into Cetacean-like paddles with five digits, which were composed of numerous phalanges and enclosed in a common skin. Teeth in a single row in both jaws, implanted in distinct sockets. Vertebrae amphicoel-ous, with the neuro-central suture persistent; singleheaded ribs are attached to the long diapophyses of the dorsal vertebrae. Sacral vertebrae two. Quadrate bone Suturally united with the skull. A parietal foramen. No sclerotic ring. Neither sternal ribs nor sternum are and Lower Eocene by Champsosaurus, in the Trias by Rhyncho-saurus, Hyperodapcdon, and in the Permian by Protcrosaurus, Sphenosaurus, Telerpeton (?), Saurosternum (?).

Order 8. Lacertilia. Lizards. Vertebrae generally proccelous, with short or rudimentary transverse processes; sacral vertebrae not exceeding two; ribs single-headed. Os quadratum articulated with the skull. Parts of the ali-and orbito-sphenoid regions fibro-cartilaginous. Temporal region without, or with only one, osseous bar. Limbs four, two, or absent; when they are present, a sternum with sternal ribs and a pelvis are developed. Copulatory organs paired; urinary bladder present. Integuments with horny or sometimes bony scutes.

For the numerous recent genera see Lizards. Distinguidiable representatives of the order appear first in Jurassic formations and thence downward to our period: Acrosaums, Ardeosaunis, Pleuro-saurus, Saphdosaurus, Atoposaunis, and Homoeosaurus from the Oolite; Nuthetes, Saurillus, Macellodon from the Wealden; Dolicho-saurus, Acteosaurus, Coniosaurus, Rhaphiosaunis from the Chalk. From Tertiary formations in Europe numerous small remains are known, whilst those described from Australia belonged to much larger forms, showing more or less affinities to the Lizards of the present Australian fauna.

A distinct division of this order includes the extinct Mosasaurians, which arc, in fact, the Pinnipedes among Lacertilians. Their limbs, of which they had two pairs, are transformed into paddles; by their long Snake-like body and large size the marine Reptiles form the nearest approach in nature to the modern creature of imagination, the “Sea-Snake.” There is no question that they deviate more from the Lacertilian type than any of the other fossil forms mentioned above, especially in some of their cranial characters, which are more Ophidian. Hence Cope placed them into a distinct order of Reptiles, Pythonomorpha. Their body was covered with osseous scutes.

Besides Mosasaurus, remains of which have been known and described since the year 1766, a number of other genera from Cretaceous rocks of Europe and North America have been distinguished by Owen, Cope, Marsh, and Dollo: Liodon, Clidastes (fig. 2), Sironectes, Platecarpus, Baptosaurus, Diplotomodon, Edestosmmis, Holosaums, Lestosaurus, Tylosaurus, Pteryeollasaunis, Plioplatecarpus.

Order 9. Ophidia. Snakes. Vertebrae procoelous, extremely numerous; no sacrum; ribs single-headed. No chevron bones on any of the vertebrae. Not only the quadrate bone is movably articulated to the skull, but also the Suspensorium and the bones of the palatal maxillary apparatus are movable; brain capsule entirely osseous. No quadrato-jugal arch. No foramen parietale. Rami of the mandible united by ligament. No trace of anterior extremities, and posterior only sometimes rudi-mentally indicated. Copulatory organs paired; urinary bladder absent. Integuments folded into regularly arranged scales.

For the numerous recent genera see Snakes. Fossil forms are scarce, and do not appear before the Eocene (Laophis, Ralaeophis, Raleryx).

Order 10. Chelonia. Tortoises and Turtles. Cervical and dorsal vertebrae not numerous. The dorsal vertebrae and expanded ribs (with the exception of Sphargis) are united into a carapace, the elements of which are immovable, and which is completed ventrally by a number of dermal bones, a true sternum being absent and replaced by a plastron. All the bones of the skull are suturally united, with the exception of the mandible and hyoid; the dentary portion of the mandible consists of one bone only. Pectoral arch consisting of the scapula, with which the precoracoid is united, and the coracoid. Clavicles are represented by the anterior elements of the plastron. The pelvis consists of the usual bones, but is not attached to a sacrum. Two pairs of limbs. No teeth, these being replaced by horny sheaths of the jaws. Copulatory organ single. Integuments consisting of horny scutes covering the carapace, and of scales and tubercles on the soft parts.

For the numerous living genera see Tortoises. Remains of extinct Tortoises are found from the Trias downwards, but they do not show any approximation to some other Reptilian type, or indicate a successive development. The most generalized type, Sphargis, is not older (according to present evidence) than some of the more specialized genera, its earliest representative being the remarkable Rrotostega from North-American Cretacean formations. Some of the Tertiary fossils exceeded in size the largest of living forms, suchasthe Himalayan Colossochelys, the German Macrochelys, the North-American Atlantochelys. (A. C. G. )

The Anatomy of Reptiles.

As the principal features known of the anatomy of extinct Reptiles have been sufficiently noticed in the several separate articles devoted to them, this chapter will deal almost exclusively with the general structure of living forms.

Inasmuch as the class of Reptiles is one of the classes which make up that great primary zoological division known as “vertebrate animals,” they of course possess all those structural characters which are common to that division (see Vertebrata). They also possess in common a certain number of structures which they share with

Birds (see Sauropsida), and which will be indicated in our notice of the different sets, or systems, of organs which compose the bodies of the animals of which this article treats.

Every Reptile has a body made up of a head, a trunk, and a tail, though, as in some Lacertilia and many Ophidia, these regions are not marked off one from another by any constriction or noticeable alteration of diameter. The posterior aperture of the alimentary tube always marks the termination of the trunk and the commencement of the tail. In some kinds of Reptiles—as, e.g., in the genera Anguis and Amphisbaena amongst the Lacertilia, and in such forms as Typhlops and Uropeltis amongst the Ophidia —the whole body consists of little more than a very elongated trunk with a small head at one end and a short or even quite rudimentary tail at the other. A neck may be interposed between the head and the trunk; this, however, is generally short, as in the Lacertilia and Crocodilia, but may be more or much elongated, as in the Chelonia. It was extraordinarily long in the extinct Sauropterygia— like that of a Swan.

The head may be very large, as in the Crocodilia and extinct Ichthyopterygia, or small, as in the Sauropterygia, or very small indeed, as in Typhlops and Uropeltis. It always contains the organs of taste, smell, hearing, and sight, but there may be, as in many Lizards and all Snakes, no external indication of an ear, and the eyes are almost hidden by the skin in Snakes such as Typhlops, and certain Lizards such as Amphisbaenians and some Skinks. The mouth may be very large, as in the Crocodiles, or very small, as in Typhlops.

The trunk may be exceedingly elongated, as in the instances just above referred to, or relatively very short and broad, as in the Chelonia.

The tail may vary in development from its rudimentary condition in Typhlops to a length which exceeds that of the body several times, as in not a few Lacertilia. Its distal end may be prehensile and form an important grasping organ, as in almost all Chamaeleons.

Besides these regions, there are generally two pairs of limbs,—one pectoral, the other pelvic,—though these may be altogether wanting as far as regards any external manifestation, as in all Ophidians and certain Lacertilians like Anguis and Ophisaurus. Internal rudiments of limbs may, however, be present when there is no external indication of them, as will be pointed out when describing the appendicular skeleton.

There may be but one pair of limbs, and these pectoral, as in the Lizard Chirotes; or there may be but one pair, which are pelvic, as in the Lizards Pseudopus, Lialis, and Ophiodes.

The pectoral and pelvic limbs are, as a rule, pretty equal in development, and they may be very much so, as in Chelonians and the Sauropterygia. Both may be exceedingly small, as in many Lizards, such as a number of the Seincidae, or both may be relatively large, as in Cheloni-ans. In no existing Reptile with four limbs does either pair very greatly exceed the other in length and size, but in extinct Pinosauria the pelvic limbs were greatly in excess, while the reverse was the case with the extinct Ornithosauria.

The extremities never terminate in more than five distinct digits, and the number may be reduced to one in front, as in Rhodona, or one behind, as in Pibamus. The extremities may end bluntly and be undivided, as in land and marine Chelonians, and as in the extinct Ichthyop-terygia and Sauropterygia. The pectoral and pelvic limbs are generally not very divergent in form and structure, and they may be wonderfully alike, as in the existing Tortoises and in the extinct Ichthyopterygia and Sauro-

pterygia. They were, on the contrary, extremely divergent in certain Dinosauria, and still more in the Ornithosauria.

Every Reptile has a body composed of organs of nutrition, circulation, respiration, secretion, reproduction, sensation, and motion, supported internally by a solid framework, the internal skeleton or endoskeleton, and enclosed in a firm investment, constituting the external skeleton or exoskeleton.

The External Skeleton.

The external investment of the body consists of two layers. The outer of these, the epidermal layer, or epidermis, is of an epithelial horny nature and never becomes bony. The deeper or dermal layer, the dermis, is a fibrous structure which may become bony. Neither hairs nor feathers are developed.

The exoskeleton is characterized in this class of animals by being composed of distinct superficial thickenings placed side by side and separated one from another by thinner interspaces. According to the size and form of these thickenings they are known by different names. If they are very small and rounded they are called “tubercles,” and such we see on the body of the Chamseleons and Geckos. If they are large, flat, and not overlapping, they are called shields, and such we see, e.g., on the head of the true Lizards. If the hinder part of each thickening is more or less prolonged over the anterior part of one or more next behind it, structures of this kind are called scales, such as we find dorsally clothing the bodies of most Lizards and many Serpents. If the median part of each such scale is still more thickened longitudinally, then such a scale is said to be carinate. In most of these cases the epidermis itself is also more or less thickened locally, as well as the subjacent dermis, remaining thin in the folds or interspaces. The dermis may be ossified, forming dense bony plates, or scutes, beneath the epidermal investment. The whole body may be thus clothed, as in the Lizard Cyclodus and others, or the bony plates may be confined to parts of the back, as in some Crocodilians. The development of the exoskeleton is carried to the highest degree in Chelonians, when large osseous plates form, in the Land Tortoises and Terrapins, a complete and continuous bony case for the body, invested externally by a rich corneous epidermis, and becoming internally anchylosed with the endoskeleton itself.

In most Ophidians the body is clothed with scales above and with large transversely elongated shields beneath (single or double beneath the tail), though the body may be entirely invested by small scales except the head, as in Typhlops, or by tubercles, as in Aerochorclus.

Sometimes, as in Cerastes and the River Jack, two horny appendages are erectly developed over the nose and sometimes, as in Herpeton tentaculatum, cutaneous appendages project from the snout, or the snout may be exceptionally produced. The skin of the side of the body just behind the head may form a distensible fold, as in Naja, and there may be, as in Python, a claw on each side of the vent, which claw is a rudiment of the pelvic limb, as will be explained in describing the appendicular skeleton. A peculiar cutaneous depression exists between the nostril and the eye in Crotalus and the other Pit-Vipers. For full details on these subjects see the separate articles on the orders.

In the Lacertilia we find a number of different cutaneous conditions which have been already noticed in describing the various groups systematically. It will then suffice here to remind the reader that the Amphis-baenians have quadrate shields over the entire body except the head, arranged in transverse rings, and that in such forms as Chaleis the scales are also verticillate, while in the Scincoidea and Anguidae they are imbricate, and on the Chamaeleons granulate. Tho head may be covered with large shields, as in the Lacertidse, or with small scales like those of the body, as in the Monitors, and there are often long sharp spines on the head and body, as in Grammatophora, Phrynosoma, and Moloch. The integument may also extend out from the body along the back and tail, as in Basiliscus and Lophura, or from beneath the throat, as in Iguana, or largely across the neck, as in Chlamydosaurus, or on cither side of the tail, as in Ptychozoon, or from each side of the body so as to be distensible and to serve as a parachute, as in Draco ; while in the Ornithosauria it passed from the elongated hand to the body and leg as in the wing of the existing Bats. It has also been before stated that in certain cases different genera are distinguished by pores, Le., the apertures of small cutaneous sacs placed on the inner side of each thigh or in front of the cloacal aperture. Folds of skin may invest the digits and constitute webbed feet, as in some Geckos, as well as in Crocodiles and Terrapins, or may bind the digits in two opposite bundles, as in each extremity of the Chamaeleons. Normally each digit is terminated by a claw.

In Grocodilia the epidermal thickenings do not overlap as in some Lizards, but form conspicuous prominences in the dorsal region, w , hich serve as specific characters, and which have bony plates beneath,—which plates may, as in Alligators, exist on the belly as well as the back, and may form continuous rings round the tail, those of each anterior row overlapping those of the row next behind. Not all the digits are provided with claws. The feet are webbed.

The Chelonia present considerable differences as to the exoskeleton. The Mud Tortoises, Trionyx, have a soft epidermis, and Sphargis has a coriaceous outer layer of integument covering a carapace divided into small sub-hexagonal shields. In the other Chelonians there are large epidermal shields, which may overlap, as in the Tortoiseshell Turtle ( C. imbricata) and others, or may be conterminous, as in Testudo and Emys. These shields form a mid-dorsal series and two lateral rows on either side, while there are two longitudinal series on the ventral side of the body.

Beneath the epidermal layer of the integument osseous plates are found, which plates do not coincide either in number, size, or shape with the epidermal shields which (save in Trionyx and Sphargis) cover them. Their condition in Sphargis is quite peculiar. In the skin of its back there are imbedded a great number of small plates flexibly united in a mosaic-like pattern. Seven longitudinal rows of these plates (one median, six lateral) differ from the rest by their large size and raised surfaces. On the ventral surface of the body there is one large thin median [)late—the epister-mini, together with other very slender ossifications forming a very imperfect bony framework. All these latter bony plates, however, are very imperfectly ossified, with numerous vacuities. In the Land Tortoises and Terrapins, on the other hand, we have the exoskeleton in its greatest perfec-tion. On the back there is a series of ten median plates, the first one of which is called nuchal and the last one pygal. On each side of these series and suturally connected therewith is a series of large lateral plates also suturally united together and with the median plates. Finally, a series of marginal plates suturally connected together and with the foregoing complete a bony investment of the back which is complete and continuous, and which is known as the carapace. On the ventral surface of the body nine other bony plates form another continuous shield termed the plastron. The most anterior pair correspond with the bones known as clavicles in Man and many other animals. The azygous plate between and behind them answers to the episternum of many animals. The carapace and plastron are united at the sides of the body, but are separated medianly in front and behind to allow the protrusion and retraction of the head and the four limbs and tail. In Chelonia similar plates exist, but they are less developed, and merely form an imperfect species of investment, with many vacuities between the plates. The same is the case in Trionyx, wherein the marginal plates are also wanting.

The skin of the neck and limbs is covered with scales. The skin of the neck may develop fimbriated processes and caruncles, as in Chelys, and the nose may be produced into a short proboscis, as in Trionyx. True claws may be absent, as in Sphargis, or there may be but one on each foot, as in Chelone, or two, as in Caretta, or three, as in Trionyx, or four or five, as in Testudo and Emys. The claws may approximate in form to hoofs in some of the large Land Tortoises. There may be a web between the digits, as in Emys, or the whole extremity may be united into a solid paddle, as in Chelone.

In all cases the skin of the jaws is found thickened and condensed so as to form a horny beak with a cutting edge.

In many Chelonians there are two pairs of glands on each side just in front of the junction of the plastron and carapace, while in the Mud Tortoises, Trionyx, there is yet another gland on each side in front of the margin of the plastron.

The Internal Skeleton.

The endoskeleton of Reptiles, as of most Vertebrate animals, consists of parts which are divisible into two categories :—(a) those which form the skeleton of the head and trunk, i.e., the axial skeleton; (6) the parts which form the skeleton of the limbs, i.e., the appendi-cular skeleton.

The Axial Skeleton.—In describing the axial skeleton it will be well to begin with that part of it which belongs to the trunk, leaving the more complex skeleton of the head, f.e., the skull, for subsequent consideration. Skeleton of the Trunk.— The backbone, spinal column, or spine consists in all adult Reptiles of a series of ossi-fied vertebrae, many, almost all, of which are separate and not anchylosed one to another. Nevertheless the spinal or vertebral column varies in its structure much more in the class of Reptiles than even in the Mamma, lia, and very much more than in the class of Birds, with which the Reptiles are so much allied. This variation consists in differences not only as regards the number of regions or vertebral categories and the extent and struc-ture of each region, but also as regards the form of the individual vertebrae and notably the form of the vertebral centra.

There may or may not be distinct cervical vertebrae with or without movable ribs. The first two vertebrae are differentiated as axis and atlas, and in front of the latter there may be a rudiment of another vertebra, which has been distinguished as the proatlas. There are always dorsal vertebrae, some of the ribs of which may not, but more generally do, join a sternum. These dorsal ribs are generally movable, and may be, as in Serpents, organs of locomotion. They may, on the contrary, be firmly fixed by suture one to another as in Chelonians. There may or may not be lumbar vertebrae, and two or more (in some extinct forms many) vertebrae may unite to form a sacrum. There are always caudal vertebrae, and these generally have chevron bones beneath them. Sometimes vertebrae which are not sacral become anchylosed together, as in the dorsal vertebrae of Chelonians. Articular processes always connect together adjacent vertebrae which are not thus anchylosed, and there may be accessory articular processes peculiar to the class, and which will be shortly described later. As to the form of the vertebral centra, they may bo flat in front and behind, or biconcave (amphicoelous), or biconvex, or with a ball behind and a cup in front (pro-coelous), or with a ball in front and a cup behind (opistho-coelous).

In the Crocodilia all the above-mentioned regions are distinct, there being usually 9 cervical, 11 to 12 dorsal, 2 to 3 sacral, and about 40 caudal vertebrae. In existing species all the vertebrae are procoelous except the atlas, axis, sacral, and first caudal vertebrae. The adjacent sur-faces of the centra of the sacral vertebrae are flat, and the centrum of the first caudal is biconvex. The atlas consists of five pieces, and the odontoid bone is not anchylosed to the axis. The caudal vertebrae are elongated and com-pressed, and, except the most anterior and posterior, support chevron bones. Ribs are very generally present. Those attached to the atlas and axis are single in origin. Each rib of the other cervical vertebrae bifurcates at its upper end into a tubercular and a capitular process, which respec-tively articulate with the neural arch and centrum of their supporting vertebra, and the interval thus left in the succeeding vertebrae forms a canalis centralis. The ribs of the middle five cervical vertebrae so expand distally as to impede the lateral flexion of the neck. The neural arches articulate by suture with the vertebral bodies. The dorsal ribs become attached to processes which pass out from each vertebra to the tubercular and capitular processes of the ribs respectively, and their situation with respect to the neuro-central suture changes by degrees, through the vertebral series, till in the twelfth dorsal one long trans-verse process, passing out above the neural central suture, supports both processes. Thence backwards these arti-culating surfaces approximate till at last there is but a single articular surface between each rib and its sup-porting vertebra, as was the case in those of the atlas and axis.

The dorsal ribs consist of two pieces—the distal piece remaining cartilaginous; and most ribs support an imper-fectly ossified processus uncinatus, nearly as in Birds, which extends backwards from the distal portion of its ossified piece (fig 4). From seven to nine of these ribs have ossified sternal ribs which serve to connect them with the sternum. The lumbar vertebrae have only long transverse processes which arise above the neuro-central suture. The sacral vertebrae support very stout transverse processes, each of which includes a rib element and becomes anchylosed to the centra only at a late period of life, as do the comparatively long and slender caudal transverse processes. Inferior processes, hypapo- physes, which are azygous, descend one from beneath the centrum of each of the more posterior cervical and anterior dorsal vertebrae.

The sternum consists of an ossified rhomboidal plate, with the hinder side of which two pairs of costal cartilages articulate. A narrower piece extends backwards from this plate (connected with it by ligament), and ends in two diverging processes. With this the other sternal ribs articulate. A long slender bone, the interclavicle, or episternum, lies in a median groove of the sternal plate, and extends forwards beyond it.

There is a so-called abdominal sternum made up of a series of seven or eight slender bones which lie in the aponeurosis of the external oblique muscle of the abdomen behind the true sternum and in front of the pelvis. It lies at a lower level than the sternum, and has no direct connexion with the vertebral column.

In Hatteria, the only living member of the order Rhynchocephalia, as well as in the extinct species, the vertebral bodies have flat or concave surfaces in front and behind. There are 8 cervical, 14 dorsal, 3 lumbar, 2 sacral, and 36 caudal vertebrae. There is no persistent neurocentral suture in Hatteria, though there may be in some extinct forms of the order. Rudiments of the proatlas are sometimes present. The atlas consists but of three pieces, and the odontoid bone is anchylosed with the atlas, and is concave anteriorly. An autogenous hypapophysis is wedged into the inferior interspace between the centrum of the axis and the third vertebrae, and similar parts are developed thence backwards to beneath the seventh and eighth vertebrae. Hatteria has the faculty of reproducing its tail after mutilation. When the tail is broken the fracture takes place in the middle of one of its centra and not between two adjacent centra. This is owing to the fact that each caudal vertebra is divided into an anterior and a posterior part (fig. 5), and is weakest at this line of junction which passes behind the transverse process.

The first rib is attached to the fourth vertebra. Those of the ninth and the following vertebrae attain the sternum.

The more posterior ribs become connected with the abdominal sternum. All the ribs are single at their proximal ends, a bifurcation being scarcely indicated even at the most anterior one. Processus uncinati are fully developed.

The sternum is a rhomboidal, semi-cartilaginous plate, with a medianly situated long and slender episternum which unites with a pair of clavicles. An abdominal sternum is more fully developed than in any other living Reptile. It consists of about twenty-five transverse rods, each of which is composed of three pieces. These rods are connected and disconnected with the ribs in an alternate manner, every other rod being suspended from a pair of the true ribs.

Lacertilia.— In this extensive order of living Reptiles, the vertebrae are procoelous except in the Geckotidae and Uropeltidae, where they are biconcave. There may or may not be distinct cervical, lumbar, and sacral regions, and the number of vertebrae, generally considerable, may be very large. The distinctness of the vertebral regions depends on the development of the anterior and posterior limbs. When a cervical region can be distinguished, there are never more than nine such vertebrae. Only in rare instances are there distinct lumbar vertebrae. The sacral vertebrae are never more than two. The neural arch is always anchylosed to the centrum in adults. The atlas consists of three parts, and the axis may or may not have the odontoid bone anchylosed to it and convex in front. Ribs are attached to most of the cervical as well as to the dorsal vertebrae; but the former are not expanded distally as in the Crocodile, and thus the latter do not support uncinate processes. The more anterior ribs show two proximal articular surfaces, but these never diverge into distinct capitular and tubercular processes as in the Crocodiles, nor, as in the latter, do any of the dorsal vertebrae develop double, superimposed transverse processes. The more anterior (usually the first three or four) dorsal ribs are connected with the sternum by sternal cartilages. Those behind may be similarly connected with the diverging backward prolongations of the sternum, or may be directly connected with their fellows of the opposite side, as in the Chamaeleon, a median cartilage being joined on either side by the sternal cartilage continuous with an ossified rib. In Acontias and other limbless Lacertilians which have but a rudimentary sternum, or none, the corresponding ribs of the right and left sides are connected across the mid-ventral line as they are in Chamaeleo. In Draco the more posterior ribs are greatly prolonged, and their distal cartilages are bent backwards. This is to enable them to support the wing-like membrane which extends from either side of the body to serve as a parachute. In those Lizards which have a lumbar region, transverse processes are there developed. The caudal vertebrae (except the most anterior and the small posterior ones) have chevron bones, which are not generally anchylosed to the vertebrae which support them.

In addition to the ordinary articular processes, there are in Iguana certain accessory articulating structures such as are commonly found in the vertebrae of Serpents; these will be described in the next section.

The sternum consists of a rhomboidal semi-ossified or cartilaginous plate, which is sometimes continued backwards into a pair of long diverging processes. There is generally an episternum, which is often T-shaped, but it may be absent, as in Chamaeleons. In the limbless Lizards the sternum is cartilaginous, and there is none whatever in some forms, as, e.g., in Amphisbaena and Typhline.

In many Lizards, notably in the commonest English Lizard, the tail if broken off can be reproduced. In them the centra of the caudal vertebrae have a vertical median division similar to that already described in Hatteria.

In Ophidians the number of vertebrae is generally very large, and may exceed four hundred. They are all procoelous, and the ball behind each is nearly hemispherical. There is no distinction of cervical, lumbar, or sacral vertebrae; but all the vertebrae after the atlas may be considered as either dorsal or caudal. The mode of articulation between the vertebrae is more complex than in almost any Lizards.

In addition to the ordinary articular processes (or zygapo-physes), which are here broad and flattened, often with an accessory process, there are two noteworthy structures. The first of these is called the zygosphene, and consists of a wedge-shaped process with two articular surfaces, which projects forward from the anterior surface of each neural arch. The other is called the zyg- antrum, and is a corresponding excavation with two articular sur faces on the hinder side of the neural arch, and receives the zygo-

Sphene of the vertebra next behind it. It was structures such as these that were referred to in the last paragraph as existing so exception ally amongst Lacertilians in Iguana.

The atlas and axis have a form similar to that already described as existing in the Lacertilia. Long azygous hypapophyses nearly always depend from the centre of the anterior trunk vertebrae, or even from the whole of them, being especially large and numerous in some of the most poisonous Serpents, e.g., Crotalus and Naja. In Dasypeltis scaber some of these processes in the anterior dorsal region are made to minister to alimentation,—their tips being coated with tooth substance, and penetrating within the alimentary canal, as will be again mentioned further on.

The ribs assume the function of locomotion, and are therefore very movably articulated to short transverse processes. Each has two proximal articular surfaces, but they are close to gether, there being no diverging articular and tubercular processes.

Each rib terminates in a short car tilage. The caudal vertebrae may, in rare instances, be very few, and they may be very numerous—from five to two hundred. They do not possess chevron bones, but bifold depending hypapophyses, and they have transverse processes which also are generally bent downwards.

Sometimes, at the limit between the body and the tail, the transverse process, or the rib, as the case may be, bifurcates or develops an ascending process, as, e.g ., in Boa, Naja, and Echidna.

No Ophidian has any sternum.

Chelonia.— The Tortoises and Turtles present a spinal structure remarkably divergent from that of all other Reptiles, and especially divergent from that of Ophidians. Nevertheless the Chelonia agree with the Ophidia in having no sternum, and in having at least a portion of the vertebral column formed for extreme mobility, in spite of the excessive rigidity and immobility of the trunk. Only in Sphargis do we find a structure generally resembling that of other Reptiles and diverging from that common to other Chelonians. With the exception of Sphargis, the structure of the vertebral column of which will be subsequently noticed, the Chelonians present the following characters. The endoskeleton of the dorsal region is intimately united with those ossified exoskeletal plates which have been already described (supra, p. 447) as investing both dorsally and ventrally the entire trunk. The median series of plates are united with the neural spines and arches, and the lateral plates are similarly united with the ribs, so that the carapace is formed both of endoskeletal and exoskeletal elements intimately united. The constancy of the number of vertebrae is very exceptional, as is also the very small number of those of the body. There are always 8 cervical, 12 dorsal, and 2 sacral vertebrae. The number of caudal vertebrae varies, but is never great. The cervical vertebrae have very small processes, whereby they are better fitted for great mobility. They vary greatly as to the form of their centra, some being opisthocoelous, others procoelous, others biconvex, while one at least is flattened both in front and behind— the arrangement differing even in different species of the same genus. The atlas consists of three pieces, and the os odontoideum is separate. The neuro-central suture persists. The centra of the first ten dorsal vertebrae are amphicoelous, and but loosely connected with twin neural arches, each neural arch being superimposed over the posterior half of one vertebra and the anterior half of the vertebra next behind. The sacral vertebrae have either stout ribs Suturally attached or transverse processes anchy-losed to the vertebrae. The caudal vertebrae are procoelous, and generally have a pair of separate descending processes, which may (as in Ghelydra) unite distally and form chevron bones.

In Sphargis the endoskeleton is quite distinct from the exoskeleton. Its neural arches are very loosely united to the centra, so that they can be separated with the greatest ease. The trans verse processes of the caudal vertebrae also remain unan-

chylosed to their centra. The dorsal vertebrae pass so gradually into the caudal that the boundary can only be determined by the somewhat in creased thickness of the transverse process of the two sacral vertebrae. The summits of the neural arches are somewhat dilated (as if from superincumbent pressure) or obtusely keeled. The ribs are not much expanded, their heads fitting into a hollow formed by the centra of two vertebrae together with the neural arch superimposed upon the two. They become shorter and narrower behind, that of the tenth dorsal vertebra being even smaller than the sacral ribs.

The Skull.— The anterior portion of the axial skeleton, or cranium, differs markedly from that of every other class of Vertebrates, while it presents a much greater diversity of structure than does the cranium of Mammals or of Birds. It differs from the cranium of the lower Vertebrate classes by its more complete Ossificationand by a greater prolongation backwards of the nasal cavity, which causes a greater expanse and density of the palatal structure. The skull, however, is not so much ossified as in Mammals, and the bones do not become anchylosed together so quickly and certainly as in Birds. The occipital region always consists of four occipital elements, and there is an ossified basisphenoid in front of a well-developed basioccipital. The skull almost always articulates with the atlas by a single occipital condyle. The lower jaw is always suspended to the skull by the intervention of a quadrate bone with which the os articulare of the mandible articulates. Besides the last-mentioned bone the mandible consists of as many bones as in Fishes, with the addition of a supra-angular and a complementary bone.

The bones of the cranium may form a very solid and very continuous open case, with no mobility save that of the lower jaw; or it may consist of bones several of which are so conditioned as to allow much mobility to several other parts. In all cases, however, the side wall of the anterior part of the cranial cavity is very imperfectly ossified.

The skull of the Crocodilia is distinguished from that of all other Reptiles by its very extensive bony palate, which exceeds in completeness that of even any Mammal save the Anteaters and Cetaceans, for not only the maxillae and palatines but also the pterygoids—all as expanded bony plates suturally united—concur in its composition in all existing Crocodilians (though not in the extinct Teleosaurus or Belodon), and the pterygoids surround the posterior nares. The skull forms a solid whole composed of bones united by suture except at the anterolateral and median boundaries of the cranial cavity, where it is cartilaginous or membranous. There is an interorbital septum. The quadrate bone is immovably fixed and of large size, and unites with the pterygoid, but by its upper and inner surface only. The alisphenoid is a large broad bone. The tympanic cavity is completely enclosed by the prootic and opisthotic (the latter being united with the exoccipital), the squamosal, the postfrontal, and the basioc-cipital and basisphenoid. It opens into the mouth by three apertures, one median and two lateral, which terminate complex canals having communications among each other. There are two lateral, quasi-zygomatic arches to the skull —an upper one formed by the postfrontal and squamosal, and a lower one by the maxilla, jugal, quadrato-jugal, and quadrate. There is no foramen in the parietal region of the skull, and there is an azygous parietal bone and frontal. On either side of the hinder region of the skull the periotic and exoccipital bones form large parotic processes. There is a distinct perforated lachrymal. There are two vomers, which are generally hidden in the palate by the junction of the extensive inaxillae and palatines. There are a pair of nasal bones. Various cranial bones are pneumatic, including the os articulare of the mandible. The hyoid is very simple, and consists only of a broad cartilaginous or partly osseous basihyal, with two bony cornua, not directly connected with the skull. There is a very small cartilaginous stylohyal on the upper hinder part of the quadrate.

Hatteria.— The skull of this living type of an extinct order resembles that of the Crocodilia in that there is a lower zygomatic arcade formed by the quadrato-jugal bone interposed between the malar and the quadrate, as well as a superior zygomatic arcade formed by the squamosal and postfrontal, and in that the quadrate bone is immovably fixed between the pterygoid, squamosal, and quadrato-jugal. The palate is pretty complete with wide plate-like ossifications, still it is much less so than in the Crocodiles; but the posterior nares are much more anteriorly situated —very near the anterior end of the palate—and are on each side, being each bounded by the premaxilla in front, the vomer internally, the maxilla externally, and the palatine behind. At the side of the skull we find a bone distinguished as the “columella,” which passes upwards from above the suture between the pterygoid and quadrate to the parietal, to which it is attached by a slip of cartilage. It is a flattened bone, somewhat expanded above and below, and constricted towards its middle. The lateral wall of the skull at the part which in the Crocodile is occupied by the alisphenoid, and in front of that part is not osseous but fibro-cartilaginous. There is an interorbital septum. The postero-lateral region of the skull consists, as in the

Crocodiles, of two outstanding “parotic processes,” made up of the cxoccipital, prootic, and opisthotic bones,— beneath which is the “columella auris.” The basisphenoid sends down two processes to abut against the pterygoids. The parietal is perforated by a small median fontanelle. The premaxillae are separate, and together form a sort of beak, their large teeth becoming thoroughly anchylosed and united with the bones supporting them. The nasals are double, and each sends forth a process (somewhat as in Birds) from its outer anterior angle.

The Lacertilian skull is formed mainly upon one of two diverging types of structure—(1) that of ordinary Lizards, and (2) that of Charmeleons. In both the quadrate bone is almost always movable and the inferior zygomatic arcade is wanting, though generally represented by a ligament; the palate is incompletely ossified, and the rather anteriorly situated posterior nares bounded internally by the bifold vomers. In the ordinary Lizard type the skull has the appearance of consisting of a system of osseous bars connecting the solid occipital parts (with its pair of parotic processes) with a flattened cranial roof and the more or less well ossified snout. The skull has an interorbital septum. The lateral walls of the cranium are, as in Hatteria, fibro-cartilaginous, though they may contain some insignificant ossifications; and a “columella,” as in Hatteria, generally ascends from the pterygoid to the parietal. The last-named bone sends a backward prolongation to the parotic process and squamosal, and is movably united to the occipital; and thus, through the imperfect ossification of the cranial parietes, the facial part of the skull is capable of more or less flexion upon the occipital part There is generally a superior zygomatic arcade formed by the junction of the postfrontal with the squamosal; and, very generally, the orbit is enclosed posteriorly by a junction of this postfrontal with the malar. The basi-sphenoid sends down (as in Hatteria) two processes to abut against the pterygoids, which again join the quadrate bones. An os transversum unites the pterygoid, palatine, and maxilla of either side. The maxilla is thus a fixed bone; the premaxilla is generally single, and sends a median process backwards. The nasals, frontale, and parietals may be single or double. There is generally a parietal fontanelle.

By very rare exception, as in Monopeltis, there may be two occipital condyles, that (median) portion which is formed from the basioccipital aborting.

The hyoid consists of two pairs of cornua, whereof the anterior is generally the longer, attached to a median portion from which azygous a bifold process may proceed both anteriorly and poste riorly.

In the Amphisbaenians the skull is more solidly and continuously ossified than is usual in Lizards, though there is no columella and though the low ali-and orbito-sphenoidal regions are membranous. The parietal is not movably articulated to the exoccipital, and the facial part is solidly ossified and not movable upon the hinder portion of the skull.

The orbits are not enclosed behind, and there is no superior zygomatic arcade.

The skull of Heloderma is very remarkable in that it has no zygomatic arch whatever, and in that the pre-and postfrontal bones unite and exclude the frontal bone from the margin of the orbit.

The skull of the Chamaeleons has even more the aspect of an osseous scafffolding than has that of ordinary Lizards in spite of the absence of a columella. This is owing to the presence of a long supraoccipital arcade formed by a long posteriorly and inwardly extending process of the squamosal, which joins the adjacent side of the singularly prolonged and upwardly and backwardly extending process of the parietal, which itself is solid ly united to an up wardly extending process of the supra-

occipital. Thus the facial part of the skull is not movable upon its occipital portion. The orbits are enclosed by bone, and there is a superior zygomatic arcade, the post frontal joining the squamosal behind and the malar in front. The frontal bone is small and single. There are a pair of narrow nasals, but these do not form the boundary of any part of the anterior nares, but are excluded therefrom by the junction of the prefrontals with the maxilla, and these two bones may be prolonged so as to form great horn-like processes. The pterygoids do not articulate with the quadrates, and there is no interorbital septum. The hyoid has its posterior cornua much the longer, and a bony median basihyal.;

The Ophidians, like the Lizards, have skulls which are formed on more than one type:—(1) those of the ordinary wide-mouthed Serpents; and (2) those of the Serpents with a very narrow gape, such as we find, e.g., in Typhlops and Uropeltis.

The wide-mouthed Serpents, or Eurystomata, have a skull which in some respects is much less completely ossified and more movable than in ordinary Lizards, while in other respects it is more ossified and less movable. Thus the lateral walls of the anterior parts of the cranial cavity are well ossified, so that the anterior part-of the skull is no longer movable on the occipital segment, while on the contrary the total absence of both zygomatic arcades, the non-union directly of the palatine with the vomer, the laxity of union of the premaxilla and maxilla, and especially the movable condition not only of the quadrate but also of the squamosal (often an elongated bone) from which it is suspended, all give an excessive mobility to the facial part of the skull. To this it may be added that, at the symphysis, the rami of the mandible are only united by soft, very extensible tissue. There is usually but one premaxilla, and that is edentulous. The palatines are usually connected with the maxilla by transverse bones, while the pterygoids connect them with the quadrate bones. There is no interorbital septum, and no fontanelle in die cranial roof. The basisphenoid is prolonged forwards into a long bony rostrum, on the upper surface of which the cartilaginous rods (the per sistent trabecu- lae cranii) ex tend forwards to blend with the median cartilage of the ethmoi dal region. The supraoccipital is excluded from the margin of the foramen magnum by the exoccipital. The frontal bones descend laterally to the dorsum of this basi-sphenoidal rostrum and then turn inwards to meet together in the median lines on the floor of the cranial cavity. The parietals also descend laterally but unite with the basisphenoid by suture. There are a pair of nasals, and also lachrymals and postfrontals, but there is no jugal or quadrate jugal. The palatines do not bound the posterior nares behind. They are widely separated, and their long axes are longitudinal. The maxillae may be long and may support a number of teeth, as in most non-venomous Snakes, or maybe very short and support a single large fang, as, e.g., in Vipers.

The small-mouthed Serpents, or Angiostomata, have the pterygoids separated from the quadrates. The squamosal is small or absent, the quadrate being attached directly to the cranium. They have no postfrontal and no transverse bone, while the palatine bones have their long axis transverse, and meet, or nearly meet, on the under surface of the skull. The two rami of the mandible are also closely united together. In other details of cranial structure they agree generally with the Eurystomata.

The hyoid is rudimentary, and only consists of a pair of cartilaginous threads, medianly united and lying side by side beneath the trachea.

In the Chclonians the skull presents certain resemblances to that of the Crocodil-ians. Thus the quadrate is immovably fixed and its upper part is joined by the pterygoid, and there is a quadrato-jugal bone. The pterygoids and palatines unite by suture and form horizontal plates beneath the basis cranii.

Nevertheless these bones differ widely from their homologues in the Crocodiles inasmuch as the posterior nares open in front of the pterygoids and are bounded by the palatines and the azygous vomer. The epiotic bone is generally quite distinct from the exoccipital. There are large parietals, which send down a process that serves the purpose of the absent alisphenoid. In front of this, the sides and front of the cranial cavity are unossified.

There are a pair of frontals, and in front of them a pair of bones which bound the anterior nares above. There may be one or two premaxillae. Sometimes, as e.g., in Chelone, the parietal, postfrontal, jugal, and squamosal send out plate-like processes which unite and form a sort of false outer skull covering in the temporal fossa, and quite external to the real outer wall of the cranial cavity. Thus the cranium of these Reptiles is, as it were, at the opposite extreme to that of the Serpents as regards massiveness, solidity, and the immovability of its several parts one on another.

It maybe excessively flat and depressed, as in Chelydra.

The dentary bone of the mandible is azygous, as in Birds.

The hyoid consists of two pairs of cornua, whereof the anterior may or may not be the larger, attached to a broad, more or less cartilaginous, or variously ossified median portion.

The Appendicular Skeleton.—The appendicular skeleton of Reptiles, like that of Vertebrates generally, consists of a pair of limb girdles (pectoral and pelvic), with a pair of skeletal appendages proceeding from either girdle. Each such skeletal appendage has also, normally, the typical differentiation into (1) a single upper limb bone, (2) a pair of lower limb bones, (3) a group of small foot-root bones or cartilages (carpus or tarsus), (4) a series of middle foot bones (metacarpus or metatarsus), and (5)

a group of small bones (phalanges) arranged in series according to the number of digits, but the number in each digit varying in different digits and in different groups of Reptiles.

Every trace of an appendicular skeleton may, however, be wanting, as is the case in most Ophidians.

There may be a pectoral limb girdle without any rudiment of a fore-limb skeleton, as in Anguis, Acontias, and Amphisbaena. There may be a pelvic girdle without any rudiment of a hind-limb skeleton, as in at least some, if not all, Typhlopidae. Very rarely there may be both rudimentary pectoral and pelvic girdles without any trace of limb skeleton, as in Amphisbaena. Thus, of the two categories, (1) limb girdles, and (2) girdle appendages or limbs, the former is the more constant, as we never find rudimentary extremities and limbs without any trace of a girdle, while the contrary we do find here and there. The Limb Girdles.— Each girdle consists of two lateral halves, and each such lateral half further consists of two divisions which diverge from the articular surface offered to the limb by such lateral half. From that articular surface one division descends dorsally and does not connect itself with its fellow of the opposite side. The other ventral division passes inwards and somewhat downwards and normally does connect itself, directly or indirectly, with its fellow of the opposite side. The dorsal ascending division is generally single, and consists of two parts in serial succession. The ventral division consists normally of two or more parts, which, though diverging, pass ven-trally side by side, or one in front of the other. Each girdle normally connects itself with the axial skeleton either towards the dorsal or ventral aspect of the latter.

The Pectoral Girdle.— This girdle only becomes connected (except in Chelonians) with the ventral part of the appendicular skeleton,—to wit, where it abuts against either side of the sternum. In its most complex condition —that found in some Saurians, e.g., Iguana— the dorsal division consists of a scapula (with a forwardly extending process—the mesoscapular), and is continued upwards into a suprascapular; while the ventral division consists of a coracoid, which abuts against the sternum, and from which three parts (the precoracoid, the epicoracoid, and the meso-

coracoid) diverge forwards and inwards, and also of a clavicle, between which and its fellow of the opposite side an interclavicle is interposed. This girdle normally in Reptiles, as in all other Vertebrates, embraces more or less of the axial skeleton externally; only in adult Chelonians it becomes drawn in within the circuit of the ribs.

In the Ophidia , as has been said, there is no pectoral girdle.

In certain Sauria it is in its simplest possible form, as, e.g., in Acontias and Typhlosaurus, where each lateral half consists of a minute ossification representing the clavicle and coracoid, which is not connected with its fellow of the opposite side by any hard structure, as both sternum and interclavicle are wanting. It is also quite rudimentary in Amphisbaena, but it is fairly developed in Chirotes. Its most complex condition in Saurians has been already described. The Chamaelcons have a simple girdle consisting of a long and narrow scapula with suprascapula and a long and narrow coracoid, the anterior part of which envelops (or is overlapped by) its fellow of the opposite side, while its hinder part joins the sternum. There is no clavicle or interclavicle.

Hatteria has both a scapula with a mesoscapular process and a cartilaginous suprascapula, also a coracoid with a large cartilaginous epicoracoid. There is an interclavicle, the diverging anterior arms of which, as clavicles, are connected by ligament with the scapula.

The Crocodilia have a simple girdle, consisting only of a scapula with a cartilaginous suprascapula and a coracoid without processes or epicoracoid, nor are there any clavicles but only a median anteroposteriorly directed interclavicle.

In the Chelonia the girdle lies between the dorsal and ventral shields. The dorsal division is a columnar scapula, which ascends to be connected by ligament or cartilage, which sometimes contains points of ossification, with the transverse process of the first thoracic vertebra. Of the bifold ventral division, the anterior bone is a direct continuation of the scapula, and connects itself with the interclavicle of the plastron, whilst the posterior bone is a coracoid and ends freely (there being no sternum). In Sphargis the end of the right coracoid underlies that of the left coracoid.

The Pelvic Girdle.— This girdle only becomes connected with the dorsal part of the appendicular skeleton—to wit, where it abuts against the sacral vertebrae.

In general each of its halves consists of a dorsal division more or less simple and columnar, the ilium, united to the vertebral column by cartilage, and of a bifold ventral division, the parts of which, pubis and ischium, unite in the middle line by the intervention of a median longitudinal cartilage or ligament, a process extending forwards from the front margin of the more anterior part—the pubis—while an azygous bone, the os cloacae, extends backwards from behind the symphysis formed by the junction of the more posterior part, the ischium, with its fellow of the opposite side. The ilium, pubis, and ischium form the acetabulum.

Although it has been elsewhere already described, it may be well again to mention here that in certain extinct Reptiles not only is the ilium greatly expanded above antero-ρosteriorly but the pubis sends back a long slender post-pubis nearly parallel with the ischium and closely resembling the so-called pubis of Birds.

In the Ophidia the pelvic girdle is generally entirely absent, and, when a rudiment is present, that rudiment is never united with the axial skeleton. It may consist merely of a pair of subparallel slender pubic spicules or cartilages, as in Typhlops, or of a rudimentary ilium, pubis, and ischium on each side, as in Cylindrophis, Ilysia, Stenostoma, and Boa . A rudimentary pelvis also exists in Python, Eryx, and Tortrix.

In Saurians the girdle may also be detached from the axial skeleton and most rudimentary, as in Lepidostenon, where it consists of no more than in Typh- lops, and in Anguis, where each half of it consists of an elon-

gated ossicle with three processes correspond-

ing to the three nor-

mal pelvic bones. It may be even more simple and yet attached to the vertebral column, as in Acontias, Pseudopus, and Ophisaurus.

In all Saurians with ordinary hind limbs the pelvic girdle is fully developed.

The Chelonians have long ilia nearly vertical in position and with a cartilaginous margin. The pubis and ischium form an acute angle, and are only connected with their fellows of the opposite side by ligament. There is no os cloacae.

Hatteria has a la-certilian pelvis. The pubis has a small forwardly extending process, and the ischium a much more prominent backwardly extending one.

In the Crocodilia the acetabulum is formed by the ilium and ischium only, and is imperfectly ossified internally. The two ischia are united by synchondrosis, and each develops a forwardly extending process contributing to close the acetabulum, from which the pubic bone extends forwards, downwards, and inwards. The two pubic bones are only united together by membrane.

The Chelonia have the pelvic girdle, like the pectoral one, enclosed between the carapace and plastron. In most forms it is not united with either shield, the ilium being merely attached to the transverse processes of the sacral vertebrae. In some forms, however, as in Chelys, Chelodina, Pelomedusa, and others, the ilia firmly unite with the posterior plates of the carapace, while the ischia and pubes unite with the plastron. The three bones concur to form the acetabulum, and the two pubes and the two ischia respectively unite in ventral symphyses. The space between the pubis and ischium of either side, the obturator foramen, is in Chelone and Sphargis separated from that of the other side by a ligament only, which proceeds from the ischiatic symphysis forwards to the pubic symphysis. In the Land Tortoises, however, the pubes and ischia so expand entrally that the obturator foramen is (on each side) enclosed by the junction of the pubis and ischium of either side at their distal ends. Each pubis has ordinarily a downwardly bent spinous process at its anterior margin, and the ischium often has a process projecting from its hinder margin. The pubes are generally widely expanded bones, very much larger than either the ischia or the ilia.

The Pectoral Limb.— The skeleton of this limb in its full and normal differentiation resembles in its main features that of Mammals; it may, however, be simplified to a greater extent than in any other air-breathing Vertebrate class, and this according to two modes of simplification. Thus it may be a relatively minute member ending in what is (at least practically) but a single digit, as in Rhodona. It may, on the contrary, be simplified by being made up of parts all so exceedingly similar that the typical differentiation of the limb can be with difficulty traced, while the digital elements seem to indicate more than pentadactylism, as in the extinct Ichthyosauri.

A peculiar complexity and extreme differentiation of this limb, however, exists, as is well known, in another extinct group, the Pterodactyles, wherein the outermost or ulnar digit is enormously elongated so as to support the wing membrane as do the four digits of existing Bats.

The following are the main conditions of the limb met with in the existing Reptilian orders. In most Lacertilia there is an elongated humerus, the proximal end of which is compressed and furnished with two tuberosities. Of the lower arm bones, the ulna is stronger than the radius, and its olecranon forms a short projection. The carpus consists of nine bones, one at the end of each lower limb, one at the base of each metacarpal, one—the os centrale—between these five and the two at the end of the midlimb bones, and one—the pisiforme—outside these latter two. There are five metacarpals and five digits, the latter composed of phalanges, which for the most part number two for the innermost digit or pollex, three for the next or index, four for the third digit, five for the fourth (generally the longest) digit, and three for the outermost or ulnar digit. In the Chamaeleons the five proximal carpals coalesce with the metacarpals, and the phalanges are 2, 3, 4, 4, and 3 respectively; the digits, moreover, are very exceptionally disposed, the three inner or radial digits being opposed to the two outer or ulnar ones. The digits may be but four in number, as in Saurophis, Gymnophthalmus, Tetradactylus, and others; or but three, as in Chalcis, Seρs, and others; or but two, as in Heteromeles, Chelomeles, and others; or, finally, but one, as in Rhodona, &c., as we have already seen. The limb may be entirely wanting, as in Pygopus, Delma, Lialis, Anguis, Acontias, and others.

In the Ophidiα the pectoral limb is entirely absent, not even a rudiment of it being found.

In Hatteria the limb is Lacertilian in form but has ten carpals.

The Crocodilia have the long limb bones well developed. The carpus has two large long ossicles articulated with the radius and ulna respectively, and a pisiforme; and an oblong bone and disk of cartilage lie between the large carpals and the five metacarpals. The third digit is the longest, and the number of phalanges of the digit from within outwards (as before) is 2, 3, 4, 4, 3.

In the Chelonia the humerus may be nearly straight, as in Chelone, or very much curved, as in Testudo. The radius and ulna, which, though susceptible of very little motion, are generally distinct, may become anchylosed together towards their distal ends, as in Chelone. The carpus has generally nine ossicles. The pisiforme may be very large, as in Chelone. There are always five digits, which —both their metacarpals and phalanges—may be very long, as in Chelone, or exceedingly short, as in Testudo. The number of the phalanges may be but two to each digit, as in Testudo, but generally it is 2, 3, 3, 3, 2, from pollex to the ulnar digit.

The Pelvic Limb.— The skeleton of this limb, like that of the pectoral one, is in its main features normally conditioned as is that of Mammals, save as to the mobility of the tarsus, as will be shortly explained. It may, however, be simplified in two ways like the pectoral limb—namely, by the great similarity and want of differentiation of its numerous parts, as in Ichthyosaurus, or by excessive reduction in the number of its parts, as in certain Ophidians, and in Saurians such as Pseudopus and Lialis.

Its resemblance to the pectoral limb, which, as we have seen, is so exceedingly close in Ichthyosaurus and Plesiosaurus, may be, in other conditions, hardly less complete in some Chelonians, such, e.g., as Chelydra. When all four limbs are fairly developed, the pelvic ones are in no existing forms so inferior in size to the pelvic ones as in the extinct Ornithosauria, or so superior in size to the latter as in some of the extinct Dinosauria, as, e.g ., in Compsognathus.

Amongst existing Reptiles the Lacertilians present us with very varied conditions. Generally there is an elongated femur furnished proximally with a trochanter on its inner side. Of the lower limb bones the tibia is larger than the fibula. A knee-pan bone, or patella, is placed in front of the junction of the upper and lower limb bones. The tarsus consists of a proximal segment made up of two large ossicles more or less firmly and immovably united by fibrous tissue to the tibia and fibula and of a distal segment, which consists of a cuboid bone and which is capable of motion upon the proximal segment, while it is firmly connected with the five metatarsals. Thus the flexion of the foot upon the leg takes place, not as in Mammals between the whole tarsus and the leg-bone, but between the distal and proximal segments of the tarsus itself. The outermost or peroneal metatarsal is more or less bent toward its proximal end. The fourth digit is the longest, and the number of the phalanges of the digits, from within outwards, is 2, 3, 4, 5, 4. In the Chamaeleons the distal tarsals coalesce with the metatarsals, and two inner or tibial digits are opposed to the three outer or peroneal ones. The foot may have but four digits, as in Cαmp>sodactylus, Tekrαdαctylus, and others; or but three digits, as in Sep>s, Heteromeles, and others; or only two, as in Chelomeles, Rhodona, and others; or but a single one, as in Chalcis. There may be but a very small and slender femur, to which a still smaller tibia unites a rudiment of a tarsal ossicle at its distal end, as in or but a rudiment of a femur and tibia only, as in Pseudo-pus∙, or the limb may be entirely wanting, as in Anguis, Acontias, Chirotes, Amphisbaena, and Lepidosternon.

In the Op>hidia the limb is generally wanting, and there is never any rudiment of the tarsus or digits, but there may be a rudiment of a femur, as in Stenostoma, or of a tibia as well as a femur, the tibia ending in a hooked process, as in Cylindrophis, Ilysiα, and Boa.

In Hatteria the limb is as it normally is in Lacertilians.

In the Crocodilia there is a well-developed femur, and also a tibia and a fibula. The tarsus has two proximal bones (less closely united than in Lizards), whereof that adjoining the fibula has a large calcaneal process. The distal segment of the tarsus consists of two rounded ossicles on the peroneal side and a thin plate of cartilage on the tibial side. There are four long tibial metatarsals supporting digits and a rudimentary fifth one to which no rudiment of a digit is attached. Of the four digits the third is generally the longest, and, like the fourth digit, has four phalanges. The second digit has three, and the innermost, or hallux, but two.

In Chelonians the femur has a strong, rounded articular head, which forms a marked angle with the body of the bone. Sometimes, as in Emys and Trionyx, there are two trochanters separated by a groove. The lower limb bones are always distinct. They are longest in the Land Tortoises, and shortest in the Marine Turtles. There is no patella. The tarsal bones vary by coalescence from eight to six in number. They are exceptionally flattened in Chelone. In Testudo the metatarsals are short, but are longer than are the metacarpals, whereas the reverse is the case in Chelone. There are always five digits, except in Testudo, where the fifth is only represented by a rudimentary metatarsal. The metatarsals are shortest,in Tcsiudo and its allies, though they are not so short as are the digits of the hand. They are longest in the aquatic forms, though they are not so long in Chelone as are the digits of its hand. The number of phalanges, counting from within outwards, may be 2, 2, 2, 2, as in Testτιdo, or 2, 3 3 3, 2, as in Trwnyx, or 2, 3, 3, 3, 3, as in Chelone. Myology.

The muscles of four-footed Reptiles other than the Chelonians are arranged in a general way on the same fundamental plan as in the Mammals, though the determination of the true homology of many of them is more or less difficult if not impossible now to determine. The muscular masses are thus arranged in a similar longitudinal manner on the dorsum of the trunk, and expand into large continuous horizontal sheets of fibres in the ventral region, while for a greater or less extent longitudinal bundles of fibres underlie the vertebral bodies in different parts of the neck and trunk, and prolongations backwards of the dorsal and ventral muscles clothe the skeleton of the caudal region. Muscles like the temporal, masseter, pterygoid, and digastric of Mammals help to open and shut the jaws of Reptiles. Others descend from the dorsal region of the spine to the pectoral and pelvic girdles and to the limb bones, which latter are furnished with flexors and extensors, abductors and adductors, in essentially the same way as are the limbs of birds.

There are two special deviations from this more normal type of structure. We find one of these in the Serpents, which, being limbless and without a neck, and requiring an extraordinary mobility in the parts of the axial skeleton, have the muscles which clothe the trunk raised to their highest degree of multiplication and differentiation. The other exceptional type is furnished us by the Chelonians, which, having a perfectly rigid body and long neck and limbs singularly situated, have the muscles of the trunk atrophied to an extreme degree, the neck richly supplied with muscles, and also the limbs, while the limb muscles are so strangely different, in either origin or insertion, from those of other animals that their true nature and correct designations do not seem as yet to admit of precise and accurate determination.

The Muscles of the Trunk and Tail.—In Saurians the caudal muscles often take the form of a series of hollow cones successively enclosed one within the other, while their continuations forward in the trunk become the longissimus dorsi, sacro-lumbalis, spinalis, levatores costarum, and the other muscles familiar to anatomists. Subvertebral continuations form muscles which proceed from the vertebral bodies to the inner surfaces of the ribs, which they tend to pull back—retrahentes costarum—and further forwards, such muscles as answer to the longus colli, rectus capitis, &e., of Mammals. Ventral muscles take the form of the two obliques and transversalis, but the differentiation may be greater than in Mammals, as e.g., in Iguana, where the obliquus externus consists of three distinct layers. Tendinous or harder structures may produce a segmentation in the abdominal muscles, which, under special names, are prolonged to the hyoidian cornua and mandible.

In Serpents the dorsal muscles are essentially the same as in Lizards, but are more developed, while small superficial muscles run from the ribs to the inside of the abdominal shields which are agents of locomotion. The limbless Serpent is practically somewhat like a Centipede, and moves by the successive protrusion and retraction of each pair of ribs, which serve as two feet. For each pair is attached to a ventral shield the edge of which is applied to and removed from the ground by the ribs attached to it, according as these are protruded or retracted—the shields thus serving as a number of small levers to propel the body along. The subvertebral muscle may also be very largely developed, as in Naja and Crotalus, the long hypapophyses of which have been already noted, and which serve for the attachment of such muscles. By their contraction the force of the downward flow of the poison fangs is greatly increased. That subvertebral series already mentioned as the retrahentes costarum is very extensively developed in the Ophidia.

In the Crocodilia arrangement is substantially as in Saurians, but the so-called abdominal ribs induce certain differences. Some muscles lie above, some below, and some between these “ribs.” Subvertebral muscles extend beneath the cervical and anterior dorsal vertebrae, and farther back there are retrahentes costarum.

Hatteria has special muscles inserted into the distal expansions of its ribs, which may sometimes aid its motions in a very subordinate degree, as those of Serpents are so helped in the highest degree.

In the Chelonians the dorsal muscles are well developed in the neck and tail. Bifold muscles pass from within the hindmost lateral plates of the carapace to the dorsum of the caudal vertebrae. Other muscles extend between the articular and transverse processes of the caudal vertebrae. Dorsal muscles are entirely wanting in the thorax of Testudo, butin Emys and Chelydra a longitudinal muscle lies upon the transverse processes of the trunk vertebrae. In the neck there are a number of muscles extending with various degrees of complexity between the transverse and articular processes. The neck is retracted partly by a muscle passing from it to the procoracoid and partly by a long muscle passing to the head and neck from a greater or less number of the spines and neural arches of the more posterior trunk vertebrae. Pyramidal muscles pass from the pelvis to the plastron, and oblique muscles arise from inside the costal marginal plates of the carapace and pass to the pelvis and plastron, and a transversalis extends from within the costal plates and also passes to the plastron. Λ diaphragm springs from the bodies of certain dorsal vertebrae and one or more ribs, and invests the surface of the lungs.

The Muscles of the Head.—In ordinary Saurians, the temporal muscle is embraced by the upper (in them the only) zygomatic arch, and descends from the side of the head to the coronoid process of the mandible. The masseter takes origin from the quadrate and columella. Of the two pterygoid muscles one arises from the upper surface of the pterygoid bone and the other from the os transversum. The digastric descends from the hinder part of the cranium to the posterior end of the mandible.

In the Ophidia the muscular apparatus is much more complex, as might be predicted from the great mobility of their jaws. There are on each side three elevators and several depressors of the lower jaw, and sometimes, as, e.g., in Trigonoeephahis, a muscular belly connected with one of the elevators is so arranged as to be able to compress the poison gland. In poisonous Serpents also a tendon goes from the external pterygoid to the short maxilla, so that the latter can be erected by its intervention. The Suspensorium is drawn upwards and backwards by a muscle arising from the neural spines of the anterior trunk vertebrae, and downwards and forwards by another arising from the basisphenoid. Four other muscles on either side of the head are devoted to moving the palatine apparatus.

The Crocodilia have a temporalis, an internal and external pterygoid, and a digastric. There are also a pair of sternomandi-bular muscles, and of hyomandibulars (from the cornua of the hyoid), a pair of genioglossi, and a superficial mylohyoid.

The Chelonia have only an internal pterygoid, besides the temporal and digastric. But they have also a geniohyoid and genioglossus as well as a mylohyoid.

The Muscles of the Pectoral Girdle and Limb.—In ordinary Saurians and in Crocodiles the scapula is drawn forwards and upwards by a trapezius and levator, and there are also a serratus magnus and a sternoscapular muscle, a cleidomastoid or sterno-mastoid, and generally an omohyoid. In the Chelonia the shoulder-girdle muscles are very reduced and peculiar, and no muscle draws it towards the skull, but a muscle arises from the sides of the cervical vertebrae and is inserted into the scapula. Another (smaller) passes from the second dorsal transverse process and the part of the carapace therewith connected to the scapula, which it draws backwards. Another muscle goes from the coracoid to the hyoid, and yet another—a sort of sternomastoid— from the plastron to the skull.

Lacertilians have an ordinary pectoralis and generally a subjacent small muscle passing from the coracoid to the great tuberosity ol the humerus. There is a latissimus dorsi going to the lesser tuberosity and a large subscapularis. A triceps ends by a tendon inserted into the olecranon, often containing an ossicle analogous to a patella. There is also a biceps, coracobrachial is and brachialis, anticus, with other Mammalian muscles, flexors, and extensors of the digits, with even lumbrieal muscles, but not with that perfect arrangement of perforating and perforated tendons which characterizes the highest class.

The muscles of the pectoral limb of Crocodiles, though showing many minor differences from those of Saurians, yet present a fundamental general resemblance to the latter.

It is otherwise with Chelonians. In them the pectoralis major is represented by two muscles, one a muscle extending from the median plastron plate and external border of the carapace to the inner of the two tuberosities of the humerus, and another muscle inserted beside the former and taking rise from the most anterior plate of the plastron. There is also a superior pectoralis, which arises from the coracoid and coracoacromial ligaments, and which is partly inserted into the same tuberosity and partly extends beyond it. There are also a coracobrachialis and a deltoid, but no suprascapular. All the muscles which arise from the scapula are inserted into the external tuberosity of the humerus. There is a muscle which represents the latissimus dorsi. It arises beneath the most anterior plate of the carapace, and is inserted into the external tuberosity. The muscles of the forearm and extremity are less exceptional.

Muscles of the Pelvic Girdle and Limb.—In Lacertilians there are several hind-limb muscles which have a subcaudal origin; some of these end at the thigh, while others extend to the feet. There are numerous flexors of the leg. A powerful muscle arises beneath the tail, and is inserted hy a broad tendon into the femur. From the inferior margin of that tendon another slender tendon arises, sometimes ending (as, e.g., in Iguana) in the interarticular cartilage of the knee-joint. The muscles of the thigh, leg, and foot have a general similarity to those of Mammals generally, as have those of the arm and hand, but those which represent the ham-string muscles have generally much complexity and intricacy of arrangement of their tendons and much connexion with other muscles in the popliteal space.

The Crocodilia have an adductor femoris, which arises from beneath the transverse processes of the lumbar region and is inserted by a broad tendon into the femur. An iliacus arises from the inner side of the ilium and ischium, and goes to the inner side of the femur. Several adductors proceed to the femur from the ischium. A long muscle arises from the chevron bones and transverse processes of the anterior third of the tail, and is inserted by a strong tendon into the trochanter; thence descends another tendon along the flexor side of the femur to join the tendon of origin of the gastrocnemius, which springs from the external condyle.

The Chelοnia possess an abductor femoris, which passes from beneath the transverse processes of the thoracic vertebra, and also a sort of psoas extending from their transverse processes to the ilium. Another muscle goes from the hindmost thoracic transverse processes to the femur. A muscle, attrahens pelvim, arises from within the plastron and goes to the outer process of the pubis. Another muscle which antagonizes this, the retrahens pelvim, springs from the hindermost part of the plastron and goes to the pubis. Other retractors pass from the caudal chevron bones to the front border of the obturator foramen, and another muscle with a similar origin is inserted into the ischial symphysis. The muscles of the more distal part of the limb are less peculiar, and need not be described here.

The Alimentary System.

All Reptiles agree in having an alimentary tract which begins with jaws armed mostly with teeth, rarely with horny sheaths, but never in existing Reptiles with both, though (as has been elsewhere described) such a combination is found in some fossil forms. Moreover, teeth are mostly found not only at the margins of the jaws but also on the palate.

Almost always there is a tongue, and glandular structures around the mouth pour their secretion into that cavity, which communicates, by tubular prolongation, with the ears, the eyes, and the nostrils. The mouth opens posteriorly into the commencement of a more or less prolonged alimentary canal, the anterior part of which is not, while the greater and less posterior part is, embraced by the peritoneum. At its hinder end this canal opens into a chamber called the cloaca, into which the urinary and generative ducts also open, and which itself opens beneath the hinder part of the trunk by a roundish longitudinal or transversely extended aperture. Two accessory glands aid digestion by the products they pour into the canal. These are the pancreas and the liver, and the latter is always provided with a gall-bladder. A spleen is also always found in the vicinity of the stomach or specially digestive dilatation of the alimentary canal towards its anterior end and separated from the mouth only by the oesophagus.

The several main groups of existing Reptiles present the following characters :—

The Ophidia all possess teeth, mostly well developed and anchylosed to the bones which support them. By rare exception, as in Dasyρeltis scaber, the teeth may be quite minute,—the hypapophyses of the anterior trunk vertebra penetrating the dorsal wall of the alimentary canal and being tipped with tooth substance, and taking the place of teeth, as already mentioned in describing the axial skeleton. Teeth generally exist on the palatines and pterygoids as well as on the maxillae and mandible, and in Python and Tortrix in the premaxilla. They may be absent from the palate, as in Uropeltis. But the various conditions as to the disposition of the teeth have already been given in the systematic part of this article.

In the majority of Serpents the teeth are solid or have but their pulp cavity, but in some harmless ones one or more of the hindmost teeth which are set on the maxilla are longitudinally grooved along their convex side. In poisonous Serpents each maxilla supports a poison fang or tooth so deeply grooved that the margins of the groove meet and so convert the grooved tract into a canal, down which the duct of a poison gland passes. This fang may be the only functional maxillary tooth, as in Crotalus and Vipern, or there may be other teeth behind it, also grooved, as in Naja, or entire, as in Bwιgarus. Almost all Ophidians have a row of small labial salivary glands along either margin of each jaw, their secretion escaping into the mouth by numerous small apertures. In addition to this, some apparently innocuous snakes with grooved teeth have an additional glandular mass connected with the upper labial gland and pouring its secretion by a duct into the dental groove. The truly poisonous Serpents possess a gland placed above the maxilla and os transversum and beneath and behind the ball of the eye, and of different size and extent in different genera. In Naja it may extend for about one-sixth the length of the body, but in Callophis it may be yet greater and extend throughout nearly half the length of the entire body of the animal. The poison gland has a fibrous investment, which is often contractile from the presence in it of muscular fibres, and often jaw muscles are so arranged (as already mentioned) as to exert pressure on the gland by their contraction. A nasal gland and a lachrymal gland also convey their secretion into the mouth.

The tongue is long, bifurcated anteriorly, and extremely mobile, being capable of protrusion from and retraction into a membranous sheath, placed on the floor of the mouth beneath the ventral wall of the larynx.

The oesophagus is long. The stomach begins by a well-defined limit beside the liver, and may or may not form a curve, but is always simple. A valve at its pyloric end marks the commencement of the duodenum. The small intestine varies much as to the number of its convolutions, which are connected by bands of fibrous tissue and are not followed by foldings of the mesentery. A circular protuberance generally marks its junction with the shorter large intestine, and sometimes there is a caecum, as in Tyρhloρs, Tortrix, Python, and others. The large intestine may be simple, and its internal cavity may be augmented by valves or partial partitions. The cloaca opens externally by a transverse aperture. The liver is not subdivided into conspicuous lobes. The gall-bladder lies separate from the liver and posterior to it. The ductus choledochus passes through the pancreas, which lies behind the pylorus at the right side of the duodenum and is pyramidal (or rounded), or compact, or in separate parts, as in Hydrophis. The spleen lies immediately behind the pancreas. It is rounded, small, and generally entire, not lobed.

The Lacertilia all possess teeth along the margins of the jaws and very often in the palatines also; but it is only by rare exception, as, e.g., in Iguana, that the pterygoids bear teeth. In the C’hamaeleons the teeth are very rudimentary, little more than an enamelled dentated ridge on the margin of either jaw. The teeth of most Saurians are either acrodont, i.e., anchylosed to the free margins of the jaws (as, e.g., in Psammosaurus), or pleuro-dont, i.e., anchylosed to the inner side of the jaws, their crowns projecting above the margin (as, e.g., in Iguana). Generally more or less conical, the teeth may be acutely pointed, or extremely obtuse, as the hinder teeth of Cyclodus. Sometimes, as, e.g., in Iguana, the teeth may be compressed with a median external vertical ridge and a serrated margin. By rare exception, as, e.g., in Chlamydosaurus, the teeth of either jaw may be much differentiated. Here we have a simulation, or anticipation, of that division of the teeth into incisors, canines, and molars λvhich is so general in the class Mammalia. In the genus Hcloderma the teeth are vertically grooved so as to remind us of their structure in Serpents. The teeth indeed are more grooved than in them, for one vertical groove passes down on the antero-inner side and another on the postero-outer side of each tooth. Labial salivary glands generally exist, but are small. In Hcloderma, however, and in no other known Lizard, there is a very large salivary gland on either side of the lower jaw. The quality of its saliva is distinctly poisonous, small animals bitten by Heloderma in our zoological gardens dying as if bitten by a venomous Serpent. No other such case is known to exist amongst the Lacertilia.

The tongue presents a number of variations of form which have been already referred to as diagnostic characters in the systematic part of this article. It will suffice here to remind the reader that it may be broad and flat without any sheath, and with a pair of anterior and of posterior processes, as in Amphisbaena; or short, broad, and slightly notched in front, as in Gecko; or short with a slight bifurcation in front and two long processes behind, as in Chalcis; or with a sheath, and much like that of Serpents, as in Psammosaurus; or cylindrical and wonderfully extensile, as in Chamaeleo.

The oesophagus passes into a stomach, which is generally elongated and curved. The small intestine may be hardly at all convoluted (as in Amphisbaena) or very much so, but if so the mesentery here follows its folds. Similarly the large intestine may be short and straight, or long and with internal folds. There may be a caecum, as, e.g., in Amphisbaena and some Chamaeleons. The cloaca opens externally by a transverse aperture.

The liver is but little lobed, and its gall-bladder lies in a fissure on its left side. The pancreas and spleen usually lie between the folds of the mesentery at the junction of the small intestine with the stomach. There is generally a pair of anal glands.

In Hαtteηa the large teeth in the premaxillae become completely anchylosed with those bones, reminding us of the extinct Rhyneho-saurus and Hyperodapedon. Host of the teeth which lie along the margin of the jaws and the palatines soon wear down to form mere enamelled cutting edges to the bones, with which they become immediately anchyloscd. The extinct Dicynodonts, with their large canine-like teeth, growing from permanent pulps, behind the edentulous beak-like front part of the mouth, and those Ornitho-sauria which similarly have an edentulous beak in front of the toothed parts of their jaws, may but have carried out further and more completely that process of tooth reduction which wo find to be effected with age in Hatteria.

The liver consists of two lateral lobes.

There is a pair of anal glands.

The Crocodilia have teeth in the max-

illae, premaxillae, and mandible, but none in the palatines or pterygoids. They are implanted in distinct alveoli. The tongue is so flat and closely attached to the floor of the mouth that it can hardly be con sidered as having a distinct existence. A

transverse fold of membrane extends along its hinder border and another similar fold descends in front of the posterior nares.

There are no salivary glands.

The oesophagus is wide, and the stomach nearly circular and gizzard-like, having thick muscular walls formed of fibres radiating from central tendons. The small intestine consists of two parts,—an anterior part much convoluted, thin-walled, and lined with villi, which is succeeded by a thicker-walled part with internal zig-zag folds. There is no caecum, but a circular prominence marks the commencement of the large intestine, which is short and wide with a smooth lining. It is funnel-shaped, and opens by a very narrow aperture into a very elongated cloaca, the external opening of which is rather longitudinal.

The liver, like that of Hatteria, is in two lobes, and the gallbladder is beside the right lobe. The spleen lies behind the pancreas between the folds of the duodenum. The various viscera of the abdominal cavity lie, as in Birds, in separate serous sacs.

In the Chelonia there are horny sheaths to the jaws but no teeth, though numerous rudiments of teeth have been found in the embryo of Triοηyx. The tongue is not extensible, but is differently conditioned in different genera. There appears to be only a sublingual salivary gland, though the palate of the Land Tortoise exhibits the apertures of numerous cutaneous follicles.

The oesophagus leads to the left part of the transversely placed stomach. The extent of both the small and the large intestine varies; the latter is at its shortest in Trionyx. The cloaca opens externally by a somewhat rounded aperture.

The liver is mostly large, and in two lobes connected by one or more transverse bands of its substance. The gall-bladder lies on its right and may be sunk within its substance. The pancreas has often several excretory ducts, and the spleen is generally of large size.

The Respiratory System.

All the Reptilia breathe air from the first moment of their separate existence, and are never furnished with anything in the shape of gills. The apparatus by which their respiration is effected is always a pair of sacs or lungs —whereof one sometimes aborts—into and from which air is introduced and removed by the intervention of an azygous tube, the trachea, which, passing forwards ventrally to the oesophagus, or beside it, opens in the floor of the mouth behind the tongue. The more or less dilated most anterior portion of the azygous tube is the larynx, which may become a vocal organ.

In the Laeertilia the external opening of the larynx may, by rare exception, as in Phryηosoma, be placed in front of the hind-most margin of the tongue, so that the larynx seems to perforate that organ, but is in fact merely enclosed by the posterior, exterior, and median junction of two lingual processes. A membranous or cartilaginous epiglottis may protect the entrance to the larynx as in Mammals. The larynx may be composed of one cartilage, which is produced anteriorly into two arytenoid processes, but generally these latter are distinct cartilages. Folds of membrane or vocal cords may exist, as in the Geckos and Chamaeleons, and the latter have also a wide membranous sac connected with the larynx. The trachea is generally short, but may be long, as in Amphisbaena and Lepidosternon. It is never convoluted, and its cartilages may or may not form complete rings. It ends posteriorly by dividing into two bronchi, which are usually very short, but may be of moderate length, as in Psamrnosaurιιs. The lungs are generally of about equal size, but in the Snake-like Lizards the right lung is the longer, and sometimes, as in Typhline and Acοntias, the left lung may be quite rudimentary. The lungs may be simple bags or may give out lateral processes or pouches of varying extent. In the Chamaeleons their hinder halves are prolonged into narrow tubular processes. Each lung is enclosed in a fold of peritoneum.

The Ophidia have the opening of the larynx behind the tongue rather prominent, with only a rudimentary epiglottis. The nature of their prey and their mode of eating do not readily expose them to the danger of small particles of food finding their way into the trachea. The cartilaginous framework of the larynx is very elongated. The trachea has its more anterior cartilages in the form of complete rings. The lungs are unsymmetrical in all the genera, but much more so in some than in others—one lung entirely aborting in Typhlops, Aeroelwrdus, and Viρera amongst others. The two lungs are both of tolerable size in Python, Boa, and Eryx, which have the bronchi leading from the trachea to the two pulmonary sacs. These sacs may or may not be divided into subordinate cells towards the hinder end of each. Sometimes part of the trachea itself may be dilated dorsally into cellular prominences like an accessory lung, as in Hydroplds, or ventrally, as in Aerochordus. A pulmonary sac may extend not only far backwards but also forwards to the hyoidean region, as in Heterodon.

In the Chelonia the opening of the larynx or glottis is longitudinal. It may be furnished with a membranous epiglottis, or may have none, as in Testudo. There may be cricoid and arytenoid cartilages in addition to main cartilages, but the details of structure differ in different genera. There are no vocal cords. The trachea and bronchi vary in length, the former being long in most forms, the latter in Testudo. In Cinixys the trachea and bronchi arc contorted. The lungs arc invested anteriorly and on their ventral side by peritoneum, and also by the diaphragm as they lie between it and the carapace, and therefore they do not project freely into the abdominal cavity.

The Crocodilia have no epiglottis, but the larynx is attached by tendinous fibres to the front part of the shield-like basihyal. The larynx consists of a ring-shaped principal cartilage and arytenoid cartilages. There are folds which serve for vocal cords. The trachea is long, with two short bronchi. The former is generally straight, but may be contorted. The more anterior tracheal cartilages are incomplete dorsally; those of the hinder part and of the bronchi are generally complete. Each lung consists of pouches or cells, the cavities of which open into each other, and communicate with the cavity of the bronchus by the lateral openings just mentioned. The lungs are enclosed in pouches of peritoneum, and lie, freely suspended, in the body cavity.

The Vascular System.

The vascular system of Reptiles consists of a sanguineous and a lymphatic system, and the former is further subdivided into an arterial and a venous system, as in the higher Vertebrates, though the latter two are less completely differentiated. In all there is a heart, which consists of at least three distinct cavities, namely, two auricles (which are almost always distinct) and a ventricle, which latter may or may not be completely subdivided into two distinct chambers, a right and a left ventricle. Reptiles differ from the higher Vertebrates in the heart always giving rise to at least two great vessels, which ultimately join to form a single vessel, and from these all the arteries are given off. Most of the blood of the hind limbs and tail passes either through a portal system in the liver, or else in the kidney, on its road to the heart. That which goes to the liver goes to it for the most part through the anterior abdominal veins or vein. The venous blood is conveyed to the right ventricle through a rhythmically contractile sinus venosus. The lymphatic system is well developed, with large reservoirs, and communicates freely with the venous system by a pair of rhythmically contractile so-called “lymphatic hearts.”

The Heart and Arterial System.—In all the existing Reptiles except the Crocodilia—that is to say, in the Rhynchocephaliα, Laccrtilia, Oqjhidia, and Chclonia—the two auricles are divided by a complete septum (except in some Chelonians), but the ventricle is only imperfectly divided into aright and left chamber. Of these the latter is the narrower, the more dorsal in position, and mostly has thicker walls, and communicates directly with the left auricle. The right chamber of the ventricle is broader, more ventral, and posterior, and mostly with thinner walls, and communicates directly with the right auricle. No arteries proceed from the left chamber, but three proceed from the right chamber, one of which, the pulmonary artery, goes to the lungs, and the other two constitute the trunk roots of the whole systemic set of arteries or the two aortae. Between the mouths of their trunk root and that of the pulmonary artery a muscular ridge or valve extends, which imperfectly divides the right chamber of the ventricle into two cavities, which, during the latter part of the ventricle’s contraction, become completely divided by it so as to shut off’ the contained blood from any further access to the pulmonary artery. These great arterial vessels thus leaving the heart are at first closely connected together and are invested with the pericardium, and sometimes, in Chelonians, their investment has been observed to contain striated muscular fibres, thus reminding us of the “bulbus arteriosus” of Amphibians. Afterwards the great arteries proceed in diverging and opposite directions, one aorta arching over to the right and the other to the left, and then meeting and uniting on the dorsal side of the heart to form by their junction the single great dorsal aorta.

Amongst the Lαccrtilia, the Monitors are remarkable for the almost complete septum between their ventricular chambers. In many Lizards the great arteries going to the head may be so connected with the two primitive arterial roots as to form two arches called aortic arches on either side, but in 1he Monitors, Cliamaeleons, and Amphisbaena these complications are wanting, there being but a single aortic arch on cither side. Generally the right trunk root, or right fundamental aortic arch, after sup]dying small arteries to the heart itself, gives off’ a common carotid artery, which divides into a right and a left carotid, and these subdivide to supply the head and neck. It also gives off the subclavian arteries for the fore limbs - and arteries to the trunk. The left trunk root, or left fundamental aortic arch, gives off arteries to the viscera, and then anastomoses with the right trunk root, the two anastomosing to form the single dorsal aorta, which passes backwards beneath the bodies of the vertebrae, and gives off branches to the'stomach and the viscera, and to the kidneys, sexual glands, hind limbs, and tail.

In the Op>hidia the heart is elongated and very distant from the head, and there are of course no limb arteries given off from the aortae.

The heart is also distant from the head in the Chelonia, but it is broad in shape and lies above the coracoids. Striated muscular fibres invest the aortic roots in Emys.

In the Crocodilia the ventricle is subdivided by a complete septum into two thoroughly distinct chambers, and a trunk root or fundamental aorta proceeds forth from each,—the left aorta and the pulmonary artery proceeding from the right chamber, and the right aorta from the left ventricle. Nevertheless, though there is here no communication between the chambers whence these two aortae arise, there is a communication between these two aortae themselves, and that not only when they anastomose after arching different ways, as in all other Reptiles, but also by a direct communication between them. When they cross one another, as the aorta from the right chamber arches to the left and that from the left chamber arches to the right, a small aperture places their cavities in communication just outside the heart and close to their respective origins.

The Venous System.—The systemic veins arising in all parts of the body collect together and anastomose till their three finally formed trunks open into a more or less capacious contractile cavity, the sinus venosus, which communicates with the right auricle. The anterior two of these three final trunks are called venae anonymae, and the single posterior one is called the vena cava. The former are formed by the gradual junction of the veins of the head, neck, fore limbs, and vertebral region (jugular veins, subclavian azygous veins, &c.), and the vena cava is formed by the junction of the iliac veins or those of the hind limbs, together with the veins of the rest of the body.

The veins of the alimentary canal, spleen, and pancreas, and the abdominal veins (running between the peritoneum and the abdominal muscles) or vein—there being one in the Ophidia— commonly collect and unite to enter the liver to form a portal system.

In the Ophidia the veins of the alimentary canal, generative organs, fatty appendages, pancreas, and spleen thus unite, while the caudal vein with some veins of the generative organs and intestine go to form a subordinate secondary circulation in the kidney or reni-portal system. In the Faeertilia the veins of the hind limbs collect in part to form a reni-portal system, and also communicate with the abdominal veins, which join the ordinary visceral veins to form the true portal system. In the Chelonia the veins of the tail and hind limbs join the abdominal veins above the plastron, and there with others from the bladder and viscera go to form the portal system, while small branches from the abdominal veins join others from the generative organs and vertebral veins to form a reni-portal system. In the Crocodilia the caudal vein divides on entering the trank and joins the posterior limb and body veins, and goes on to form, with the visceral veins, a portal system, giving off in this way veiυs to the kidneys to form the reni-portal system.

In all Reptiles the veins of the lungs collect together and empty themselves into the left auricle as they do in all other air-breathing Vertebrates.

The Lymphatic System and Vascular Glands.—In Reptilia generally there is a pair of lymphatic hearts placed over the transverse processes of the vertebrae at the junction of the tail with the trank. Each usually opens with a small vein which communicates with the iliac vein. Besides these bodies, more or less considerable lymphatic canals follow the course of the great arterial tranks in the body and tail, and, when there are limbs, communicate with the iliac veins. Other canals accompany the aortic arches and approach and open into the venae anonymae, and others extend backwards towards these from the head and anterior limbs.

A pair of bodies which answer to the thymus gland of Mammals lie close to the jugular veins and lymphatics at the anterior part· of the thoracic cavity. They are elongated in Ophidians and roundish in other Reptiles, and they are much larger in young than in old individuals.

A thyroid exists in front of the pericardium on the ventral side of the great arterial trunks. It is bilobed in the Crocodiles.

The supra-renal capsules are yellowish bodies which lie more in connexion with the generative glands than the kidneys. They are very elongated in the Ophidia, flattened in the Chelonia, and roundish in the Crocodilia.

The Nervous System and Organs of Sense.

Reptiles, in common with other Vertebrates, have a nervous system divisible into an axial portion or neural axis made up of brain and spinal marrow, and a peripheral portion made up of the multitude of nerves which proceed from or are connected with this, and one portion of which is more or less distinctly separable and known as the sympathetic system. Reptiles also generally possess three distinct organs of sense—(1) ears, (2) eyes, and (3) nasal organs—though one or more of them may be exceptionally rudimentary and defective.

The Neural Axis.— The spinal marrow extends through nearly the whole length of the neural canal of the skeleton in the form of a long nervous cylinder with a small central cavity, with a deep furrow along the middle of its dorsal and a shallow one on the middle of its ventral aspect. It becomes more or less augmented in volume about the region of the shoulders and loins, where the nerves of the limbs are given off from it. Even where most enlarged, however, the tracts on either side of the dorsal furrow do not diverge and leave a space or sinus as they do in the lumbar enlargement of Birds. Where the spinal marrow comes to join the brain it enlarges considerably. At the medulla oblongata it is bent down at a marked angle with the more posterior part of the neural axis. The two halves of its dorsal portion also diverge so as to expose the dorsal surface of the more ventral portion in a space which is known as the fourth ventricle or ventricle of the medulla. This medulla advances forward, expanding and becoming locally differentiated to form the brain, its ventricle being continued on into a more anterior and more completely enclosed cavity known as the third ventricle. The nervous roof of the hinder part of this latter ventricle is produced into two smooth prominences placed side by side and called the optic globes or corpora bigemina (which may themselves contain a cavity), immediately behind which is an azygous nervous structure, the cerebellum, which more or less roofs over the hindmost or fourth ventricle. In front of the optic lobes are the larger rounded smooth neural masses—the cerebral hemispheres, each of which contains a cavity—the lateral or first and second ventricles, which both communicate with the anterior end of the third ventricle through an aperture termed the foramen of Munro. Between the hinder ends of these hemispheres an azygous structure projects upwards—the pineal gland—while from beneath the floor of the third ventricle another azygous structure projects downwards— the pituitary body. In front of the hemispheres are the other rounded and smaller neural masses, the olfactory lobes, which are generally elongated and contain cavities that are continuations forwards of the lateral ventricles. Three transverse bands of nervous tissue connect the structures which bound the third ventricle laterally; the first of these, placed just behind the lamina terminalis or the front boun dary of that ven tricle, is called the anterior com missure, and the nervous masses it joins are the cor pora striata. An other more pos teriorly situated band is called the soft commissure; and the third, a little farther back still, is the posterior commissure. The masses joined by those last two commissures are called the optic thalami. The brain is invested with membranes in the same general way as it is in Mammals.

In the Larertilia the cerebellum is a thin very small body projecting rather upwards, and may be transversely segmented, as in Platydactylus. In the Chamaeleons the optic lobes and hemispheres are of nearly equal size, and the olfactory lobes are neither separated off nor hollow. In the Ophidia the cerebellum nearly covers the fourth ventricle, the hemispheres are of considerable size, and the olfactory lobes may be immediately annexed to them. In the Chelonia the cerebellum is rather large, but it is only in the Crocodilia that it is marked by transverse grooves, as is the central part of the cerebellum or dermis in Mammals; the hemispheres also are of considerable volume.

In some extinct Reptilia, e.g., in the Dinosaurian Stegosαιmιs, the brain was exceedingly small, probably weighing but the hundredth part of that of the Alligator compared with the weight of the bodies of the two animals. Moreover, the cerebral hemispheres but little exceeded the optic lobes in size, while the transverse diameter of these lobes only slightly exceeded that of the medulla. The cerebellum also was very small. In the Omithosauria, however, the optic lobes were unlike in their situation those of any existing Reptiles, they being depressed and placed laterally instead of on the dorsum of the brain, thus resembling the optic lobes of Birds.

The Peripheral System.— As in the higher Mammals, so also in Reptiles, the neural axis gives off a series of special nerves, which in a general way correspond in number with the vertebrae they pass out between. Each also arises by a superior and inferior root, whereof the former is furnished with a ganglion. After the junction of these two roots the whole nerve thus formed divides into ascending and descending branches—the latter, in the trunk, running between the internal oblique and transverse muscles.

The cranial nerve which comes forth from the brain nearest the spinal marrow is the hypoglossal. It passes out through a condyloid foramen in the occipital bone, and goes to the tongue, hyoid, and larynx. A more anteriorly placed nerve, called the spinal accessory, exists except in Ophidia. It arises between the superior and inferior roots of the more anterior spinal nerves, and then enters the cranium, which it leaves again in company with that next to be noted. It supplies certain dorsal muscles of the neck or anterior part of the trunk. The next or pneumogastric nerve passes out into the spinal accessory. It is distributed to the lungs, stomach, and heart. To these, next in advance, succeeds the glossopharyngeal for the tongue and pharynx. Very distinct from the foregoing is the facial nerve, which passes out at a distinct foramen and turns rather backwards to supply the sides of the head. Next is to be distinguished the acoustic nerve, which goes to the internal ear, and in front of that again is the trigeminal, which is wont to make its exit at two distinct places, and diverges into three branches, which go respectively to the orbit, the upper jaw, and the lower jaw. Then come three small nerves destined to supply the muscles which move the eyeball; and foremost but one is the optic nerve; this crossing its fellow of the opposite side beneath the brain, the fibres of the tw’o nerves blend at their point of intersection and so form what is called the chiasma. Most anterior of all are the olfactory nerves, which proceed from the olfactory lobes to the nasal organs themselves.

In the Chelοnia the spinal accessory may take origin as far back as the root of the fourth cervical nerve. The pneumogastric and glosso-pharyngeal pass out from the skull separately as in Saurians, and not through one foramen as in Ophidians and Crocodilians.

Those spinal nerves which continue to supply the limbs form certain more or less complex unions with each other termed plexuses, and from each plexus the nerves of the fore or hind limbs, as the case may be, proceed. The plexus which supplies the nerves of the fore limb is called the brachial plexus. It is formed by the hlendingof about the sixth, seventh, eighth, and ninth spinal nerves in the Turtle and Crocodile, and the nerves it gives forth are the axillary, ulnar, radial, musculo-spiral. and median as in Mammals. Certain of the more posterior nerves unite to form a crural plexus and others just behind the former blend to form a sacral plexus, and from these the nerves of the leg and pelvic region proceed. Amongst these nerves are the crural, obturator, and especially tlιe great sciatic nerve, which passes to the back of the thigh and divides into the tibial nerves.

As to the particular spinal nerves which go to form these plexuses respectively, and as to the mode of their interlacement and mode of giving origin to the limb nerves, there is not only diversity between different genera of the same order and species of the same genus, but also between different individuals of the same genus, and even between the two sides of the same individual Reptile.

The Sympathetic Nervous System—nerves which copiously supply the viscera—is least marked in the Ophidia, in which this system is not distinct, in the greater part of the body, from the spinal nerves. Essentially the system consists of two antero-posteriorly extending nervous cords, which run on either side of the axial skeleton in its ventral aspect. Each of these two cords is joined by fibres from the spinal and cranial nerves adjacent to it except the nerves of the nose, eye, and ear. At the points of junction between the spinal nerves and the sympathetic cords there are ganglia, and from these sympathetic nerves proceed to the viscera, the heart, and the various blood-vessels.

The Ear.— The auditory organ may consist of three parts—the external, median, and internal ear. The external ear, however, hardly exists in Reptiles, for there is no external fold of skin representing the external ear of Mammals in any save in the Crocodiles, and in them it is little more than a rudiment.

The true internal ear always exists, and is composed of two parts—(1) a membranous labyrinth, containing fluid, enclosed in (2) a bony labyrinth, which has also fluid contents. The former consists of three membranous semicircular canals which open into a membranous sac, the vestibule, which is connected with a tubular structure, the membranous cochlea. It is to these parts that the ultimate fibres of the auditory nerve are distributed. The bony labyrinth is formed of the otic bones (prootic, epiotic, and opisthotic), which enclose it completely save at the points where openings are left called the fenestra ovalis and the fenestra rotunda. The latter is entirely surrounded by the opisthotic. The fenestra ovalis is partly enclosed by the prootic and partly by the opisthotic. The prootic specially protects and shelters the anterior vertical semicircular canal of the membranous labyrinth, and correspondingly constitutes that of the bony labyrinth. The posterior vertical semicircular canal is similarly related to the epiotic, and the external horizontal semicircular canal is sheltered by the prootic and opisthotic. The membranous cochlea helps to almost divide the bony chamber in which it lies into two parts called scalae, which communicate at the apex of the cavity.

Such being the innermost ear of Reptiles and an outermost ear existing only in rudiment in Crocodiles, there is also a median ear which may or may not exist in this class of animals. This median ear is the tympanic cavity or chamber. It is into this cavity when present that the fenestra ovalis looks, while the fenestra rotunda looks into the cochlea. Both fenestrae are closed with membrane, so that the fluid in which the membranous labyrinth is suspended cannot escape through them. The fenestra ovalis has fitted to the outer side of its closing membrane a small ossicle of similar shape to itself, which generally has projecting from its outer side a more or less elongated and slender ossicle, the stapes or columella auris. This rod may be wanting, however, as in Typhlops, Rhinophis, and Tortrix. When a middle or tympanic cavity exists, the stapes traverses it from the ossicle, closing the fenestra ovalis to become attached to a membrane, the tympanic membrane, which forms part of the external wall of the tympanum. Where there is no tympanic cavity, the stapes simply extends outwards amongst the muscles which lie external to the internal ear. In the Ophidia and Amphis-baenians and some other Snake-like Lacertilians there is no tympanic cavity, and there is none in Hatteria. Its presence is sometimes inconstant in those Lizards; thus in the Slow Worm, Anguis fragilis, it may exist in some individuals and not in others. When it exists, it may not show any external indication of its presence as in the Chamaeleons and some Chelonians, Generally, however, the tympanic membrane is covered by a scale of corresponding size, so that its presence is plainly marked externally.

The tympanic cavity communicates with the back of the mouth by a wide opening in Lacertilians; but in Chelonians this communication is contracted into a narrow passage, the Eustachian tube, which opens (one from each tympanum) by a separate aperture on the roof of the mouth. In the Crocodilia these passages become further complicated and connected so that, in addition to the aperture on either side of the mouth, there is also a median aperture which is connected with both the Eustachian tubes, that of the right ear and that of the left.

The Eye.— All Reptiles have eyes, although in some forms they are quite rudimentary and hidden beneath the skin, which is not at all or but very slightly modified in structure where it passes over them, as, e.g., in Typhlops and Typhline.

The eye consists of the same parts as in other Vertebrates, namely, of a nervous expansion at the back (the retina) derived from the optic nerve, a coloured lining (the choroid), a transparent medium (the vitreous humour) separated from one more anterior (the aqueous humour) by a sort of diaphragm (the iris), and a solid, transparent body (the crystalline lens), whilst the whole structure is enclosed by a fibrous membrane, the sclerotic, to form the “ball of the eye,” a superficial part of the sclerotic being transparent and distinguished as the cornea.

The ball may have the skin which invests it externally separated in front of it into two folds, the eyelids. When the skin is not so separated, then a closed sac of delicate transparent membrane, the conjunctiva, lies over the cornea between it and the skin, and when the skin is divided into folds or eyelids then the conjunctiva is divided also, one layer lying as before next to the cornea, and the other layer being reflected from the outer margin of the cornea into the inside of the eyelids which it lines. There is often a third eyelid, which can be drawn obliquely over the eye, and is called the nictitating membrane. A glandular structure, the lacrymal gland, lies on the outer side of the front of the eyeball, its secretion passing into the mouth by the lacrymal canal; another gland, the Harderian gland, may lie on the inner side of the eyeball. The sclerotic may be strengthened by bony plates being formed within it. A vascular coloured membrane, the pecten, may project into the vitreous humour from near the entrance of the optic nerve. The ball of the eye is moved by four straight and two oblique muscles, and may also be suspended by a funnel-shaped muscular sheath, the choanoid muscle. There are also special muscles of the eyelids.

In the Οphidia the eye is generally rather large, but very small in the Typhlopidae and Uropeltidae. In no Ophidians is the skin over the eyes divided into eyelids, so that the sac of the conjunctiva beneath it is never subdivided. In the Eurystomatous Ophidians, however, the skin, when it passes over the eyeball, is transparent. The outer (or epidermal) layer of the skin is cast with the rest of the skin of the body. The lacrymal canal is wide, but opens into the mouth by a narrow aperture on the inner side of the palatine bone. In some Trigonoeephali the lacrymal gland extends almost all round the eyeball. The sclerotic never develops bony plates in any Serpent.

Amongst the Lacertilia, many, such as the Amphisbaenians, the Geckos, and many Skinks, have the eyelids undivided, as they are in Ophidians. Most Lizards, however, have an upper and an under eyelid, and also a nictitating membrane, and there may be a cartilaginous or bony disk in the lower eyelid. Many Skinks have the lower eyelid more or less transparent. The eye of the Cliamaeleon is most peculiar. The larger eyelids have but a minute aperture, and the two eyeballs can be rotated independently, so that their axes may be differently directed simultaneously. There is a rudiment of a third eyelid, and there is a bony plate in the lower part of the large eyelid. The Harderian gland is large, but the lacrymal is small. The lacrymal canal opens below in the outer wall of the posterior nares. In most Lacertilians there are overlapping bony plates in the sclerotic, but these are wanting in Chamaeleons and Geckos. There is mostly a pecten. In some species the lacrymal gland appears to be wanting. The nictitating or third eyelid is drawn over the eye by the simultaneous action of two curiously arranged structures. One of these is a muscle which takes origin from the postero-inner orbital wall and ends by forming a fibrous loop. The other is a tendon which passes through the loop to be attached at one end to the nictitating membrane, and at the other to the inner wall of the orbit.

In Hatteria there are eyelids—the lower with a cartilaginous disk—and a nictitating membrane. The sclerotic contains osseous lamellae, and there is no pecten.

The Crocodilia have three eyelids, and no bony plate in any part of the eye. A muscle arises from the surface of the sclerotic on its inner side and ends in a tendon which passes backwards and downwards over the optic nerve to attach itself to the margin of the nictitating membrane. There is a rudimentary pecten.

In the Chelonia the sclerotic is furnished with bony plates. The Harderian gland is small, but the lacrymal is considerable. There are three eyelids, and the nictitating one has the muscle which moves it combined with the elevator muscle of the eyelids. Both arise from the inner side of the sclerotic. One arches over the optic nerve and goes to the third eyelid, and the other goes from the outer angle of the eye to the lower eyelid. The fibres of these two muscles are closely interrelated at their origin.

The Olfactory Organ.— There are two olfactory organs in every Reptile, consisting of tracts or foldings of mucous membrane richly supplied with nerves and supported and protected by cartilaginous or bony structures. In existing Reptiles they always lie at, and extend near to, the anterior end of the muzzle, though in the Ichthyosauri and Plesiosauri they opened anteriorly far back and near the orbits. The olfactory membranes are always enclosed or supported by cartilages which proceed out from an azygous septum which divides them one from the other. Each nasal organ has an anterior and posterior opening, though the anterior openings may so meet as to form but one superficial aperture, as in the Crocodilia, and the two posterior apertures may open, not directly into the mouth, but into an azygous forwardly-extending diverticulum from it, the posterior opening of which diverticulum forms practically a common posterior termination for both the organs of smell. The nasal passages are short in all existing Reptiles save the Crocodilia, and open posteriorly far forwards—as has been already noticed in describing the skull, when the prolongation backwards of the posterior nares in the Crocodiles was also described. In the Chelonia the anterior external apertures of the nostrils are distinct though near together. Sometimes, as in Chelys and Trionyx, they are tubular, and open externally at the end of a short proboscis.

A structure called the nasal gland exists and is well-developed in the Ophidia. It is a peculiar rather soft body, often shaped like a mushroom with a very short stalk. It lies immediately beneath the floor of the nasal capsule, and the membranous wall of the cavity on which it lies is covered and protected by a bone, commonly called the “turbinal,” which extends out from the median nasal septum to the maxilla. These cavities open on the palate by narrow apertures placed in front of the posterior nares.

In the Chelonians we find a soft, egg-shaped, whitish, azygous body (without any internal cavity), also placed in front of the posterior nares in the skin of the palate, behind the palatine part of the premaxillae. It is supplied with palatine nerves.

The Urogenital System.

In Reptiles the urinary and generative systems are distinct, save as regards the approximation of their posterior terminations, thus agreeing with higher Vertebrates and differing from Amphibians, in which the renal and secreting organs generally continue throughout life more or less connected.

The Urinary System.— The urinary system of the Rep-tilia always consists of a pair of renal glands or kidneys, with excretory ducts which pass down to the cloaca. There may or may not be a urinary bladder, also opening into the cloaca. Besides these parts there are also a pair of Wolffian bodies, which are more or less aborted remnants of large organs which are always developed during embryonic life.

The Kidneys.—The kidneys are more or less symmetrically placed on the dorsal side of the peritoneum, in the hinder half of the trunk. Each consists of a mass of caecal tubules into the distal end of which a tuft of minute vessels projects, thus forming what is called a glomerulus or Malpighian body.

In the Οphidia the kidneys are least symmetrical, the right one extending the farthest forwards. They are elongated and lobed, and sometimes in such a way as to appear spirally twisted. Each terminates behind considerably in front of the cloaca. The duct of each ureter begins at the anterior end of the kidney and thence proceeds along its inner border, and accessory ducts open into it from the interspaces of the lobes of the kidneys. The two ureters open into the sides of the cloaca. In the males each opens upon a papilla in close proximity to the opening of the male sexual duct or vas deferens. In the females the ureter opens beside the mouth of the female sexual duct or oviduct. There is never any urinary bladder.

In Lacertilians the kidneys are more posteriorly placed than in Serpents. They lie at the hindmost part of the body cavity above the cloaca, and they generally much approximate together. They are also more symmetrically placed; only in the Amphisbaenians the right kidney extends the more forward, thus resembling Ophidians. There is always a urinary bladder, which is a ventral diverticulum of the cloaca. The kidneys are usually transversely furrowed. The ureters run along the inner side of the kidneys, and open into the sides of the cloaca, not into the bladder.

In Chelonians the kidneys lie near the cloaca in the cavity of the pelvis. They are rather short and thick, and more or less trihedral. Their surface is marked with many shallow meandering grooves and fewer deeper furrows. The ureters proceed as usual along the inner sides of the kidneys, and several large canals successively open from them into the ureters, which extend backwards, but to a trifling extent, beyond the kidneys. They open rather anteriorly into the cloaca close to the neck of the urinary bladder, which vessel is always present and voluminous, and is often two-horned.

The Crocodilia also have posteriorly situated pelvic kidneys, but they have no urinary bladder. The kidney is concave dorsally and flatter ventrally. Its surface has meandering convolutions separated by furrows. The ureters for the greater part of their length run deeply sunk in the substance of the kidneys. The ureters leave the hinder ends of the kidneys and run freely for a short distance to the cloaca, which they enter close behind the rectum.

The Wolffian Bodies.—These bodies lie one on each side on the dorsum of the body cavity, and each consists of a series of caecal tubes with vascular balls or glomeruli like those of the kidney, the various tubes always opening at first into a common excretory duct which leads towards the cloaca. In adults they are but small organs. In a Python 10 feet long they measure but about an inch. In Serpents generally they are slender and lobed bodies which lie close to the veins in front of the kidneys.

The Generative Organs.— Reptiles, like all the higher Vertebrates, have the sexes divided, with two sets of organs which respectively characterize male and female individuals. In both sexes, as in Birds, there is a pair of sexual glands, each furnished with a passage for the exit of its product, together with, almost always, external organs destined to effect and facilitate impregnation. Unlike Mammals, however, all Reptiles have the sexual glands placed within the abdominal cavity, and, also unlike Mammals, the male external organ or agent for copulation may be either azygous or bifold according to the group to which any Reptile may belong. Unlike the more inferior Vertebrates, however, Reptiles, with the solitary exception of Hatteria, always possess such a copulating organ, and impregnation is invariably effected internally.

The male organs consist of a pair of glands, the testes, with their ducts, the vasa deferentia, and the external organs, penis or penes. The female organs consist of a pair of glands, the ovaries, with their ducts, the oviducts, together with rudimentary representatives of the external sexual organs of the males.

The Testes and Vasa Deferentia.—These are two compact and rather small glands, consisting of a mass of caecal convoluted tubes, lying in the dorsal region of the abdominal cavity and completely invested by peritoneum, and with a dense albugineal coat of their own. From the mass of tubules a certain variable number of efferent tubes, vasa efferentia, come forth and soon unite in the single excretory duct of the gland, the vas deferens.

In the Ophidia the testes are not symmetrically placed, the right one being somewhat more voluminous and also in front of the other. Consequently the right vas deferens is larger than the left one. Each testis lies in front of the kidney of its own side, and is more or less elongated in form. The vas deferens proceeds along the inner margin of the testicle, and is a convoluted tube which narrows as it proceeds backwards. The opening into the cloaca is somewhat oblique, and is situated in a somewhat funnel-shaped depression beside the opening of the ureter.

In the Lacertilia the testes are spheroidal and almost symmetrically placed. The vasa efferentia come forth from their inner side and pass into a canal lying in a fold of peritoneum. This canal, the vas deferens, begins caecally much in front of the union of the vasa efferentia with it, and this anterior portion runs along the ventral side of the kidney in a fold of peritoneum and has the appearance of a knot of tubuli or of a body transversely convoluted. The vas deferens passes backwards in numerous close-set convolutions, and often dilates towards its hinder end. It ultimately narrows, and opens on the cloaca, beside the ureter, on a small papilla.

The Chdonia have testes which lie somewhat external to the kidneys as well as behind them. The vas deferens terminates upon a small papilla in the cloaca, but its proximal end—anterior to the junction with it of the vasa efferentia—is wide, and consists of a very complicated mass of tubes, and it may have (as in Chelodina) five or six short caecal diverticula.

The testes of the Crocodilia are of an elongated oval form, and lie partly in front of and partly on the inner side of the kidneys. The testis may be divided into two portions connected together dorsally. The vasa efferentia pass from the outer border of the testis to a vas deferens, which has rather thick walls with a marked dilatation towards its hinder end. It lies above the peritoneum, and opens at its distal end into a groove at the base of the penis.

The Ovaries and Oviducts.—The ovaries are, as in the class Mammals, the glands which correspond with the testes, but which, unlike the latter, are not composed of a mass of tubules, while each does not discharge its product into a tube directly continuous with it (as does the testis into the vas deferens) but into a tube, the oviduct, the distal end of which is open and discontinuous with the ovary save for a broad fold of peritoneum which connects them. The ovaries always lie in the dorsal part of the abdominal cavity enclosed in peritoneum.

In the Ophidia the ovaries are, like the testes, elongated and placed one in advance of the other. The right ovary is more voluminous, and the right oviduct is, of course, the longer one. The ova are so arranged within them as to form a longitudinal series. The proximal end of each oviduct shows a transversely expanded wide opening. The oviduct passes backwards in convolutions which are often spirally arranged, and it is very extensible, being lined with numerous close-set effaceable folds. The oviducts open into the cloaca by a crescentic fissure behind the opening of the rectum.

In the Lacertilia, except the Ampliisbaenians and probably some other Serpentiform Lizards, the ovaries have not their contained ova serially arranged. They may or may not be symmetrically disposed. The oviducts are usually broad and spirally disposed. Unstriated muscular fibres often exist in the folds of membrane which support their convolutions.

The Chdonia have ovaries symmetrically placed, often of a broad and flattened shape. The oviduct varies much in capacity in different parts of its course. The ovaries of the Crocodilia are compact in structure and somewhat more advanced in position than in most Reptiles. The oviduct is more uniform in diameter than in the Chelonia.

The External Generative Organs. —Λs has been already mentioned, all Reptiles have such external organs with the exception of Hatteria. In the rest of the class we always find such organs connected with the cloaca, and capable of being everted for use or retracted and hidden within or behind that chamber. The whole class is thus divisible into two groups according to the bifold or azygous condition of these parts.

In the Lacertilia and Ophidia they are bifold, and consist in the males of two hollow, invertible, imperforate, cutaneous cones placed one on each side of the cloaca, containing erectile tissue and capable of being protruded or retracted by appropriate muscles. The lining of each cone is continuous both with the external skin of the adjacent parts and also with the mucous lining of the cloaca.

A.tortuous groove which begins within the cloaca, at the aperture of the vas deferens, is continued on to the apex of the cone. When erected for use the lining membrane of the cones, with its grooves, becomes the external coat of each copulatory organ. In the females there are rudimentary but quite similar organs, just as in Mammals the clitoris of the female is present as the rudimentary representative of the penis of the male. In the Ophidia these hollow penes may or may not bifurcate distally, and if they bifurcate then the groove bifurcates also. The lining membrane of the cone may be smooth, as in Python, or spiny, as in Trigoηocephαlus and Crotalus, or may have transverse rows of soft lamellae, as in Boa marina. The Lacertilia, like the Ophidia, may have each penis single to its apex or bifurcating distally with various other minor modifications as to relative size, the form of the apex, and the appendages borne upon it. The cones are exceptionally short in the Chamaeleons.

The male Chelonia and Crocodilia have an azygous penis, and a corresponding rudimentary structure exists in the females. This organ lies at the ventral wall of the cloaca; it is not hollow or evertible, but purely distensible and so erectile. It is therefore its external coat which is continuous with the lining of the cloaca. Muscles proceeding from beneath the hinder trunk vertebra are inserted into it. The penis is imperforate, but two ridges are continued on to it from the wall of the cloaca, and so form a groove, and during erection a temporary canal, which passes along it from root to apex. At its distal end there is a prominence which, though imperforate, may remind us of the “glans” of the Mammalian penis. The whole body of the organ, including this distal prominence, contains erectile tissue. In the Chelonia the penis may divide distally, and if so the groove it bears divides also. In Chelodina it has an undivided distal end and two lateral processes. In Trionyx it subdivides distally into four terminal parts. The penis of the Crocodile has a deep groove which reaches to the extreme end of the penis, a quasi-glans projecting freely beneath it.

A few Reptiles have secondary sexual characters—notably the Chamaeleons, the males of which alone have the horns and other cephalic appendages,'which characterize certain species. In most Reptiles, however, the two sexes have hardly any distinctive external characters.

Embryology.

Most of the Rep)tiliα are oviparous, but certain of the Lacertilians and many Ophidians, notably Vipers and Sea-Snakes, hatch their eggs before they are laid; that is, they are ovoviviparous. The oviduct supplies the ovum during its exit with an albuminous investment, the white of the egg, and with a shell, or testa, which may be thin and flexible, as in the Lacertilia and Ophidia, or hard and calcareous, as in the Crocodilia and Chelonia, the eggs of which animals much resemble those of Birds.

, The embryo Reptile closely resembles in its general features the embryo Bird, and, as the process of development of the chick (which can be so conveniently studied) is now comparatively thoroughly well known (see Reproduction), we cannot here make more than a cursory mention of the leading structural changes. Inasmuch as embryonic Reptiles thus resemble embryonic Birds, it of course follows that they present all those features which embryonic Birds share with Vertebrate animals generally, such as the segmentation of the yolk, the resulting formation on its surface of the blastoderm, and its division into the three germinal layers. As in Birds, the yolk segmentation is meroblastic.

The blastoderm spreads rapidly over the yolk, but before it has half enclosed it a pyriform patch, the embryonic shield, or area pellucida, appears at its centre. The head of the embyro is formed at the broader encl of the pyriform patch. Towards its hinder end a streak of the epiblast is formed, the primitive groove, and then in front of it another longitudinal indentation, the “medullary groove,” the walls of which are the “medullary plates”; and it is this groove and plates with the parts immediately subjacent which lay the foundation of the developing body. The lining of the medullary groove becomes the cerebrospinal axis, while a longitudinal cellular rod which is formed beneath it, and which is called the notochord, lays the foundation of the future axial skeleton as far forward as the hinder margin of the cranial support of the pituitary body of the brain. The anterior end of the medullary groove shows serial enlargements corresponding with the successive portions of the adult brain, while the medullary plates close over the medullary groove and convert it into a canal which ultimately persists as the central canal of the spinal cord and the ventricles into which that canal opens anteriorly. The eyes arise as outgrowths from the brain aided and modified by ingrowths from the surface of the embryo. The ears and nasal organs arise mainly from superficial ingrowths. From the tissue on either side of the notochord and medullary groove are gradually formed the axial skeleton of the trunk and the muscles and other structures adjacent to it. The sides of the medullary plates bend down on either side and form the ventral laminae which split longitudinally, or they descend—the inner layer joining with its fellow of the opposite side to form the alimentary tube. The two outer layers form the lateral walls of the trunk, the space between the two inner and the two outer layers constituting the first condition of what is subsequently the first peritoneal cavity.

The limbs first appear as outgrowths from the external layers of the ventral laminae, but no rudiment of the limbs seems ever to be developed in the apodal Ophidians. On each side of that region which subsequently becomes the head and neck a series of perforations successively appear, and for the most part disappear, known as the visceral clefts, while their intervals are known as the visceral arches. The only visceral cleft which ever persists in the Reptilia is that which becomes the passage from the inner end of the Eustachian tube to the outer surface of the tympanic cavity. The foundations of the skull are laid in a cartilaginous investment of the anterior end of the notochord and of the incipient membranous labyrinth, whence two columnar prolongations, the tra-beculae, pass forwards on either side of the support of the pituitary body. We have seen the persistent nature of these trabeculae in the cranium of Ophidians. The central part of the facial region of the skull is formed by a cartilaginous ethmoidal process at the anterior end of the trabeculae. Hence and from the side of the auditory cartilage cartilaginous processes go forth which lay the foundation of the jaws, palatine structures, and hyoid apparatus. The circulating system in its earliest condition is very different from that which ultimately exists. At first the heart is not a tubular structure, but it gradually folds and subdivides itself. The arteries proceeding from it (and the veins converging to it) at first follow the general course of the arteries (and veins) of Fishes and aquatic breathing Amphibians. The arteries ascend within the visceral arches to meet in a dorsal aorta, as they must needs do in the animals just mentioned, seeing that in them it is the visceral arches which become the gill-bearing structures wherein alone the blood is aerated.

The urinary organs are at first represented by Wolffian bodies only, which are formed from beneath the dorsal region of the body cavity, but subsequently, as has been mentioned, they become replaced by the two kidneys. The sexual glands themselves arise in connexion with the Wolffian bodies.

At a very early stage of development the embryo as it were sinks into the surface of the ovum, while a membrane arises on all sides of it meeting dorsally over it, constituting the embryonic envelope known as the amnion. From the hind part of the abdominal region of the embryo there also grows forth a vesicle which, becoming greatly enlarged and richly supplied with blood-vessels, spreads itself out on all sides just within the egg shell, and serves as the organ of respiration for the embryo. This directly respiratory structure is the allantois. The ventral surface of the embryo remains long open and connected with the ever-diminishing remains of the food yolk. As this ventral surface closes in, the remains of the yolk or vitellus become connected with the alimentary canal, but by a very narrow tube called the vitelline duct. Before the process of development is complete, however, the last remains of the yolk become absorbed and taken up, and the abdominal wall is finally closed.

Space does not here allow of more than this brief indication of some of the leading facts of bodily development. We cannot attempt to describe the complex processes of ossification by which the first foundations of the skeleton, and especially of the skull, become differentiated into its manifold component bones. For an account of this process, and of all the other details of embryonic development, the reader is referred to the valuable treatises to be found enumerated in the following list of herpetological works.

General works on the Anatomy of Reptiles.—Cuvier, Leςons cΓAnat. Comρ., 2d cd., Paris, 1835; Meckel, System d. Vergl. Anal., Halle, 1821; Duméril and Bibron, Erpétologie Générale., Paris, 1834-54; Job. Müller, “Beiträge zur Λnat. u. Naturgesch. d. Amphibien, ' in Ztschr.f. Physiologie, vol. iv. pt. 2, 1832; Rymer Jones, art. “Reptilia,’' in Todd’s Cydopxdia, vol. iv., 1852; Stannius, Amphibien, Berlin, 1S56; Owen, Anatomy of Vertebrates, vol. i., 1866; Huxley, Anatomy of Vertebrate Animals, 1871; C. K. Hoffmann, in Bronn’s Thierreich, vol. vi., div. 3; Gegenbaur, Grundriss d. Vergl. Anal., 2d ed., 1877 (Eng. tr., Elements of Comparative Anatomy, 1878).

Osteology.—Cuvier, Ossemens Eossiles, 4th cd., Paris, 1834; De Blainvillc, Osteographie—Crocodilus, <fcc., 1855; E. Hallmann, Vergp Osteolog. des Schläfenbeins, 1837; Rυstlin, Per Bau des knöchernen Kopfes, Stuttgart, 1844; Giebel, “Skelet d. Krokodile," in GiebeΓs Ztsch. f. d. Ges. Naturw., 1877; Klein, “Skull of Crocodile,” in Jahreshefte d. Vereins fur Vaterl. Katurk. in Württemberg, 19ter Jahrg.; Parker, Shoulder Girdle of Vertebrates, Ray Society, 18G8; Id., “Skull of Lacertilia,” Phil. Trans., vol. elxx., 1879; Id., “Skull of Snake," Phil. Trans., vol. clxix., pt. 2, 1878; Id., “Skull of Turtle,” Proc. Roy. Soc., vol. xxviii., 1879, and Challenger Reports, vol. i., 1880; Id., “Skull of Chamaeleo,” Trans. Zool. <Soc., vol. xi., 18S0; B. Balfour, “Skull of Mecistops,” Proc. Zool. Soc., 1857, p.57, pi. 25; C. Gegenbaur, Untersuch, z. Vergl. Anat. d. Wirbelthiere (1 lift., “Carpus und Tarsus,” 1864; 2 lift., “Schultergürtel,” 18G5); Id., “Gliedmassen d. wirbelthiere,” in Morph. Jahrb., ii., p. 397, 1876; M. Fürbringer, P. Knochen u. Muskeln v. d, schlangenähnlichen Sauriern, Leipsic, 1870; Id., Morph. Jahrb., i. p. 631, 1876; Gorski, Ueber das Becken der Saurier, Dorpat, 1852; C. H. Brühl, Skelet der Krokodiliner dargestellt in 20 Tafeln, 1862; C. Born, “Carpus und Tarsus d. Saurier,” in Morphol. Jahrb., ii., p. 1, 1876; II. Stecker, “Carpus und Tarsus v. Chameleon,” in Sitzb. d. Kaiserl. Akad. d. Il'is- sensch. Wien, lxxv., 1 Abth., 1877; P. Albrecht, “Dinosauria,” in Bull, du Mus. Roy. d Hist. Kat. de Belgique, 1883-84; P. Gervais, “Ostéol. du Spliargis,” in Kouv. Archives du Mus., 1S72, viii.; C. K. Hoffmann, “Beiträge z. Kenntniss d. Beckens bei den Reptilien," in Niederl. Archiv f. Zool., iii., 1876; H. Rathke, Ueber d. Bau u. Entwickl. d. Brustbeins d. Saurier, 1854; W. Peters, “On the Ear Bones,” in Monatsb. d. Königl. Prcuss. Akad. d. Wissench. z. Berlin, 18G8-69-70-74; Huxley, “Ear Bones,” in Proc. Zool. Soc., 1869, p. 391; Id., “Dinosauria,” in Quart. Jour. Geol. Soc., July 1870; Id., “Archaeopteryx,” Proc. Roy. Soc., No. 98,186; Id., “Malleus and Incus,” Proc. Geol. Soc., 1869, 391; Owen, A History of British Fossil Reptiles, 1849; Id., “Carapace and Plastron of Chelonians,” Phil. Trans., 1849, pt. 1; Id., Ptérodactyles (volume of Palaeonto-graphieal Society for 1869); Id., Catalogue of Fossil Reptilia of S. Africa in Brit. Mus., 1876; Id., “Tympanum and Palate of Croeodilia,” Phil. Trans., 1850; Id., “Archäopteryx,” Phil. Trans., 1863; Id., “Permian Theriodonts,” Quart. Jour. Geol. Soc., August 1876; “Mosasauridae,” ibid,, Nov. 1877; Id., “Cynodraco,” ibid,. May 1876; Id., “Dinosaurian Vertebrae,” ibid., July 1876; II. Seeley, “Limb of Ophthalmosaurus," Quart. Jour. Geol. Soc., Dec. 1874; Id., “Plesiosaurian Pectoral Arch,’ ibid., Nov. 1874; Id.. “Chelonians,” Ann. and Mag. Kat. Hist., Oct. 1871; Id., “On Dimorphodon,” ibid., Oct. 1871; A. Gaudry, “Permian Reptiles,” in Bull. Soc. Géol. France, 3 ser., vii. p. 62, 1873; Cope, “Extinct Reptilia,” Trans. Amer. Phil. Soc., 1868-69; Id., “Homologies of Cranial Bones of Reptilia,” B. Kat. Hist., p. 194; Vogt, “Archaeopteryx,” Rev. Sei., ser. 2, ix. p. 241, 1879; O. C. Marsh, “Mosasauroid Reptiles,” Amer. Jour. Sei. and Art, vol. iii., 1872, and vol. xix., Jan. 1880; Id., “Pterosauria,” ibid., April 1872; Id., “Dinosaurs,” ibid,, vol. xvi., Nov. 1878, vol. xvii., Jan. 1879, vol. xix., March and May 1880, and vol. xxi., July 1881.

Myology.—II. Buttmann, Pe MuscuHs CrocodiH (Diss. Inaug.), Halle, 1826; S. Haughton, “Muscles of Crocodile,” Proc. Roy. Irish Acad., vol. ix., 1866; G. Rolleston, “Shoulder Muscles,” Trans. Linn. Soc., vol. xxvi. p. 609, 1868; N. Fürbringer, P. Knochen u. Muskeln v. d. schlangenähnlichen Sauriern, Leipsic, 1870; Id., Morph. Jahrb., i. p. 631, 187G; Hans Gadow, “Bauchmuskeln d. Krokodile,” Morphol. Jahrb., vii. p. 57; Gorski, Ueber das Becken der Saurier, Dorpat, 1852; St G. Mivart, “Muscles of Iguana,” in Proc. Zool. Soc,, 1867, p. 766; Id., “Muscles of Chan,telco,” in Proc. Zool. Soc., 1870, p. 850; A. Sanders, “Muscles of Platydactylus,” in Proc. Zool. Soc,, 1870, p. 413; Id., “Muscles of Liolepis,” in Proc. Zoot. Soc., 1872, p. 154; Id., “Muscles of Pteryo-saura,” Proc. Zool. Soc., 1874, p. 71; Humphrey, “Muscles of Pseudopus,” in Jour, of Anal, and Physio!., vo]. vi., 1872.

Visceral Anatomy.—Hulke, “Retina of Reptiles,” Jour. Anat. and Physiol,, vol. i., 1867; C. Stewart, “Lacrymal Gland of Turtle,” Monthly Microsc. Jour., 1877, p. 241; M. Braun, "Urogenital System d. einheimischen Reptilien,” in Λrδeifeti und Zool. Jour. Inst. Würzburg, iv. 113-228, 1877; Brücke, “Mechanik d. Kreislaufes b. d. Schildkröten,” Sitzb. der Kaiserl. Akad. d. Wissensch. Wien, 416, 1850; Id., Penkschrift d. Wiener Akad., iii., 1852, p. 335; G. F∣itsch, “Amphibienherzen,” in Reichert und Pubois Reymond’s Archiv, p. 654, 1869; Jacquart, “Coeur de la Tortue,” Ann. des Sc. Kat., 4th ser., vol. xvi. p. 303, 1861; J. Müller, “Die Lymphherzen der Schildkröten,” in Abhandl. d. Königl. Akad. d. Wissensch. z. Berlin, 1839, p. 31; M. Braun, “Bau u. Entwick. d. Nebennieren b. Reptilien,” in Arb. a. d. Zool. Zoot. Institut, in Wurzburg, v. p. 1, .1879; II. Rathke, “Luftröhre und Speiseröhre v. Spliargis,” in MüUer’s Archiv, 1826, p. 292; Id., “Aortenwörzeln d. Saurier,” in Penkschr. Wiener Akad., 1867; Tiedemann, “Blinddarm d, Amphibien,” in Meckel's Archiv f. Physiol. ; P. Gervais, “Dents de TUclodcrmes et des Ophidiens,” in Archives d. Zool. Experim., 1873, pl. 6; Ch. S. Minot, “Studies on the Tongue of Reptiles and Birds,” in Annivers. Mem. Boston Soc. Kat. Hist.. 1880; Bischoff, “Bau des Crocodilhcrzens,” in MüUer's Archiv, 1836; G. Fritsch, “Vergleich. Anat. d. Amphibienherzen,” in Reichert und Pubois Reymond's Archiv, 1869; C. S. Tomes, “Development of Teeth in Reptiles,” Proc. Roy. Soc., vol. xxiii. p. 93; Id., Phil. Trans., vol. clxv., pt. 1; Id., ibid., vol. clxvi., pt. 2.

Nervous System and Organs of Sense.—R. Rückherd, “Centralnervensystem d. Alligators,” in Ztsch. f. Wissensch. Zool., xxx. p. 336, 1878; C. Vogt, “Neurologie d. Reptilien,” in Keue Penkschr. d, Allgem. Schweiz. Gesellsch. f. d, Gesammten Wissenschaften, xiv., Neuchâtel, 1840; J. G. Fischer, Qehimnerven d. Saurier, Hamburg, 1852; St G. Mivart and R. Clarke, “Sacralplexus of Lizards,” <fcc., in Trans. Linn. Soc., 2d scr., Zool., vol. i., 1877;

Deiters, “Gehörorgan d. Amphibien,” in Archiv f. Anat. und Physiol., 1862; Kuhn, “Häutige Labyrinth d. Reptilien,” Archiv f. Mikroskop. Λnat., xx., p.,271, 1881; B. Solger, “Nasen-wandung u. Nasen-Muscheln d. Reptilien,” in Morphol. Jahrb., i. p. 467, 1876; E. Clason, “Morphol. d. Gehörorgans d. Eidechsen,” in C. Hasse's Anat. Studien, p. 300, 1879; C. Hasse, in bis Anat. Studien, p. 679, 1873.

Embryology.—F. Balfour, Comparative Embryology, vol. ίί. pp. 167-176; Id., “Development of Lacertilia,” Quart. Jour. Micr. Sei., vol. xix., 1879 ⅛Eimer, “Unters, d. Eier der Reptilien,” Archiv f. Mikros. Anat., viii., 1872; Kupffer and Benecke, "Die Erste Entwicklung am Ei d, Reptilien, Königsberg, 1878; Emmert and Hochstetter, “Unters, üb. d. Entwiek. d. Eidechsen,” Reil's Archiv, vol. x., 1811; Lereboullet, “Embryologie du Lézard,” Ann. Sc. Nat., ser. 4, vol. xxvii., 1862; H. Rathke, Entwickl. d. Natter, Königsberg, 1839; Id., Ueberd. Entwickelung d. Schildkröten, Brunswick, 1848; Id., Ueber d. Entwickelung d. Krokodile, Brunswick, 1866; Id., Die Entwickelung u. Körperbau d. Crocodile, Brunswick, 1866; L. Agassiz, “Embryology of the Turtle,” in Contrib. Nat. Hist. United States, vol. ii., 1857.

Monographs.—Bojanus, Anatome Testudinis Europaeae, 1819; Tiedemann, Anat. u. Naturgescħ. des Drachens, Nuremberg, 1811; Günther, “Hatteria,” Phil. Trans., 1867, pt. 2; Id., “Gigantic Land Tortoises,” Phil. Trans., clxv., pt. 1; Id., Gigantic Land Tortoises in British Museum, 1877; A, Fritsch, “Anat. d. Elephanten-Schildkröte,” in Abhand. d. Königl. Böhm. Gesellsch. d. Wissenschaften ; M. Salverda, Vergel. Ontleedk. Aanteekeningen over Calotes, 1863; J. H. Troschel, “Heloderma horridura,” in Archiv f. Naturg., Jahrg. 19,1853, p. 294; Peters, De Serpentum Familia Uropeltaceorum, Berlin, 1861. (ST G. M.)

Distribution of Reptiles in Time.

The first appearance of Reptiles on the surface of the globe is indicated by very fragmentary remains. Specimens of deeply biconcave vertebrae of Carboniferous age from Nova Scotia are believed to be those of a marine Saurian (Eosaums acadianus); if this view is correct, this oldest of Reptiles would bear the stamp of one of the most Fish-like of the class.

Formations of Permian age in North America as well as in Europe contain fossils with undoubtedly Reptilian characters; they are still associated with true Labyrintho-donts, and with remains which are too fragmentary to be assigned with certainty either to Labyrinthodonts or Reptiles. The vertebrae of all are amphicoelous. These Reptiles are Rhynchocephalians,—the oldest and best preserved being Proterosaumιs from the Copper-Slate of Thuringia, a Reptile about six feet in length, with a comparatively long neck (which, however, was composed of seven or nine vertebrae only), with numerous abdominal splints, a long tail, and well developed and differentiated limbs.

In the Mesozoic times the Reptilian type appears in such variety and in such a high state of development that this era has been distinguished as the “Reptilian age.” Yet we know chiefly such forms only as possessed bones of a size and solidity sufficient to ensure their preservation. Of small Reptiles, animals under or scarcely exceeding two feet in length, comparatively few have been discovered, although they too must have existed in abundance. In the Trias there appear first of the marine Saurians large Sauropterygians with narrow ossifications between the vacuities of the skull, such as Simosaurus, Hothοsaurus, and Pistosaurus from the German Muschelkalk. The highly interesting genus Heusticosaurus, the smallest of the group, with the four limbs modified into paddles, but with the hind limbs retaining the structure of those of a terrestrial animal, seems to afford evidence of this order having been developed from a terrestrial type. Fragments of true Plesiosaurus and Ichthyosaurus begin to appear in the Rhaetic bone beds of England. Also the Placodonts, the systematic affinities of which are not yet satisfactorily understood, are contemporaries of these early Enalio-saurians. The precursors of our Crocodiles were two genera, Belοdon and Steganolepis, with dorsal scutes, but with amphicoelian vertebrae and anterior choanae, neither palatines nor pterygoids being dilated into the osseous palate which is characteristic of later Crocodiles. Another order, the Anomοdontia, flourished and died in this epoch; some fifteen genera have been distinguished, all from the South-African Trias; however, this type is probably also represented in Russian formations of the same age. Rhynchocephalians continue in several genera in European and American strata. But the largest of terrestrial

Reptiles belonged to the Dinosaurs, whose presence in numerous species belonging to distinct groups, some with three, others with five toes to the hind feet, is testified by their osseous remains as well as by the tracks of their hind feet, which they left during their bipedal progression over stiff mud. These Triassic Dinosaurs were chiefly herbivorous, and already much more numerous in North America than in Europe ^Zanclodon).

This Reptilian fauna continued to flourish in the Jurassic period; the types of the Trias increased in variety; still more gigantic forms were developed; and new orders which were absent in the preceding period were added. Of the marine Saurians alone some fifty species are known from European formations: the Ichthyosauri inhabited chiefly the northern seas of the eastern hemisphere, and were replaced in the western by Reptiles of similar structure and size, but without teeth {Sauranodon) ; the Sauropterygians have considerably advanced beyond their Triassic precursors in having more solidly ossified skulls, and are also represented by a greater number of genera in America as well as Europe; of Plesiosaurus alone some twelve species are known from the Lias and seven from the Oolite. Ptérodactyles make their first appearance. Crocodilians have developed into the “Mesosuchian” type, their palatine bones being prolonged, pushing the choanae backwards to the middle of the under surface of their skull, but their vertebrae are still amphicoelian; they appear in numerous genera CPeleosaumιs) and species. Terrestrial Reptiles keep pace in development with the marine and freshwater types; the giants of the order of Dinosaurs have left their remains in a more or less perfect condition in the Jurassic strata of both hemispheres (Cetiοsaurus, Atlantosaurus, Iguanodon, Morosaurus, Apatosaurus) ; forms with three toes on the hind feet lived simultaneously with four-or five-toed ones; carnivorous types (Megalosawnts, Creosaurus, Ac.) represent in habit as well as relative size Mammalian Carnivora; they preyed upon the gigantic but weaker members of the order. The Dinosaurian type extended also into the southern hemisphere, as is testified by the West-Australian genus Deuterosaurus. The Chelonians, which appear first in the Upper Keuper, are in the Lias of highly advanced types, and not essentially different from recent families; they occur in many localities of Europe as Freshwater Turtles, chiefly Chelydidae ; but Emydidae are also represented, showing, however, a less solid ossification of the carapace than the recent forms. No distinct evidence of the presence of Marine Turtles and Trwηyx has been found hitherto in Jurassic formations.

This abundance of Reptilian life not only continues in the Cretaceous period, but is still more increased in variety and reaches its highest point of culmination. Ich-thyopterygians and Sauropterygians reached an enormous size; Discosaurus, with a neck 22 feet long and composed of sixty vertebrae, must have been the most formidable enemy to the Fishes of the sea. Moreover these large Saurians which survived from the preceding period were now joined by a new type of marine monsters with a Snake-like body and very short extremities, the Mosa-saurians, which attained to a length of from 10 to 80 feet and veritably filled the place of Sea-Serpents. Although their skull exhibits not a few Ophidian characters, their genetic relation to that order is not by any means proved. They were most numerous in the western hemisphere, some forty American species referable to many genera having been described by North-American authors; in Europe they are comparatively scarce. On the other hand no less than fifteen species of Ptérodactyles are known from European formations, all armed with formidable teeth, whilst the gigantic Ptérodactyles of North America are, with one exception, toothless. Together with the surviving Mesosuchian Crocodiles of the Jurassic period Gavial-like forms existed, and genera with posterior choanae and procoelous vertebrae (Eusuchians),—among them a true Crocodile from the Cambridge Upper Greensand. The western hemisphere exceeded the eastern as regards the abundance of Dinosaurians in this period still more than in the preceding, although it should be remembered that of the latter part of the globe in fact only a small portion has been opened up, and that the little we know of the geology of Central Asia and western China points to the probability of vast palaeontological treasures being reserved for the study of future generations. Rhynchoce-phalian genera continue in considerable variety, whilst other small-sized forms are referred to the Lacertilians. The types of Freshwater Turtles which lived in the Jurassic period pass into the Cretaceous. They appear now also in North-American strata: Chelydifilae first, accompanied or immediately followed by Ernydidx, a few Trionyx and Chelonia, and the remarkable Protostega, a precursor of Sphargis. Towards the end of the Cretaceous period its abundant Reptilian life is swept away, and not only every species but almost every Mesozoic genus disappears, a wide gap being left in our knowledge of the succession of Reptilian life between this period and the Tertiary era.

In the lowermost strata of Tertiary age a few isolated remains remind us still of the extinct Mesozoic fauna; such are one or two genera allied to the Dinosaurians (Agathαu-rnas) from the Laramie beds of North America. In other respects the Tertiary Reptiles bear already the character of the present fauna; although families or genera which are distinct from the living predominate in the Eocene, from the Miocene Reptiles gradually approach more and more the specific forms of our time. True Crocodiles (of which one species occurred already in the Cretaceous period), Gavials, Alligators have now entirely superseded the “Mesosuchian” type. The remains of Lacertilians are fragmentary and generally indistinct, so as to offer a wide field for generic distinctions. Anguidae have been distinctly traced back to the Miocene of North America. With a single exception, that of a poisonous Serpent, apparently a Vipera, the remains of which have been found in Miocene deposits at Sansan (south of France), Snakes do not appear before the Eocene, in England as well as North America; they are mostly large species, with uncertain affinities, but all innocuous (Palaevphis, Dinophis, Boctcus, Lithσphis). Their remains are scarce, and even those of the later Tertiary formations show a greater resemblance to genera which are now-a-days locally far removed than to those living in the same geographical district. Chelonian remains are numerous throughout, probably on account of the resistance which their solid carapaces offered to destructive agencies. Chelydidae, Emydddae, and Trwnycidae and also Marine Turtles continue to exist in an almost uninterrupted series, and approach so much the modern genera that, for instance, in Trwnyχ, if specific distinctions existed between Miocene and recent species, they cannot be determined in those parts of their skeleton which have been preserved. A peculiar type intermediate between the Marine Turtles and Emys existed in the English Eocene (Chelone). Land Tortoises, the most specialized type of the order, probably did not appear before the Miocene. A number of smaller forms are referable to the genus Testudo, but gigantic forms existed then as now in isolated localities, and exceeded in size the living, like the Colossoehelys of the Siwalik Hills, with a carapace computed to be 20 feet long, and the smaller Macrochelys from the German Molasse. It is extremely singular that the existence of these colossal Chelonians would seem to coincide with the period of the first appearance of the type of Land Tortoises.

Of the first appearance of most of the families of the recent fauna, and of their distribution in the Quaternary period, 1 we know next to nothing. With few exceptions the Reptilian type had dwindled to forms of such small size that their remains, if preserved, escape observation or are too indistinct for determination.

The Distribution of Existing Reptiles over the Earth’s Surface.

Serious obstacles present themselves at the present time to a satisfactory treatment of the geographical distribution of Reptiles. We have mentioned at the end of the preceding section that the geological record is much too incomplete to permit a comparison to be drawn between their distribution in the present and next preceding periods, and that we are therefore ignorant as to the modes in which their dispersal was brought about, and unable to account otherwise than hypothetically for the numerous instances of apparently anomalous distribution. And, when we limit ourselves merely to the task of describing the facts of their distribution at the present day, it is necessary for such an attempt that the whole class should have previously undergone a thorough rearrangement in accordance with the present state of science, and that the scattered contributions to the various faunae should have been critically examined and treated by the same uniform method. This is unfortunately not the case with the class of Reptilia. The systems and lists of Lαcertiliα and Ophidia which formed the bases for the treatises on the geographical distribution of these orders by Schlegel, Günther, and Wallace are buried under an accumulation of an immense number of additions of very different value, which require a uniform critical revision before they can be used in an inquiry of a general biological scope. 2

In the following notes we have been able to include the majority of the genera of Chelonians and Ophidians, with an approximate estimate of the species of each that are known at present. As regards the former Strauch 3 has done much to clear the way, although the small amount of materials known to him from autopsy interfered much with his critical judgment. Not many additions have been made to this order since the time of the publication of his memoirs. Of the numerous Ophidian genera and species we have eliminated all which are based on trivial distinctions, or are named by authors without special acquaintance with the subject. We have not entered into a full consideration of Lacertilian genera, as this would have been useless at a time when they are undergoing a revision, but have restricted ourselves to the families recently proposed by Boulenger.

One of the most important results obtained by this inquiry is that the same arrangement of the so-called primary zoological regions is not applicable to all orders of Reptiles, and that the differences in their distribution are so fundamental that they can be accounted for only on the assumption of the various orders and families having appeared and spread over the globe at very distant periods, when land and water were differently distributed over the surface of the globe. At the end of this section we shall show in a short résumé the mutual relations between the various regions with respect to the several orders of Reptiles.

The means of dispersal of Reptiles are very limited.

1 An important memoir on Indian Cheloηia is published whilst this article is passing through the press, “Siwalik and Narbada Chelσniafi by R. Lydekker, in Palaeontol. lnd., vol. iii. ser. x., 1885.

2 Whilst this article is being written, the Lacertilia are undergoing the much-needed arrangement by Boulenger (as mentioned at p. 439), who also has recently published preliminary notes on the distribution of the families of Lacertilians, which have been of great use to the present writer (Ann. and Mag. Nat. Hish, August 1885, p. 77).

3 “Chelonologische Studien,” and “Die Verbreitung der Schildkröten über den Erdball,” in Mémoires de l’Acad. de St Pétersb., 1862 and 1865.

They are much specialized in their mode of life and propagation, and ill adapted to accommodate themselves to a change of external conditions. As air-breathing coldblooded animals they are unable to withstand prolonged cold; they are therefore entirely absent in the arctic and antarctic zones; and such as escape the effect of the winter months in temperate zones by passing them in a torpid condition in well-sheltered places are not peculiarly organized forms, but offshoots from those inhabiting warmer climes. The tropical and subtropical zones are the real home of the Reptilian type, which there has reached its greatest development as regards size and variety of forms. In the north Chelonians advance only to 50° lat. in the western and to 56° in the eastern hemisphere, Lizards to about 56° in British Columbia, and close to the Arctic Circle in Europe, whilst Snakes disappear some degrees before the Lizards. Also in the south Lizards extend into higher latitudes than Snakes, viz., to the Straits of Magellan, whilst the latter do not seem to have advanced beyond 40° S. lat. and Chelonians only to 36°.

We exclude from our account of the distribution of terrestrial Reptiles those few forms which pass almost the whole of their life in the sea, and therefore belong to the marine faunae, viz., the Marine Turtles and Sea-Snakes.

1. The shores of the continents and islands of the equatorial zone are the home of the Marine Turtles. Endowed with a wonderful power of locomotion, the several species are now distributed over the greater part of this zone, occurring in the Atlantic as well as the Indo-Pacifιc; and, although some of them are common in certain districts and scarcer or even absent in others, it is probable that in the course of time their distribution will be still more general and uniform, as far as other conditions (such as access to a suitable locality for the successful propagation of their kind) will permit. Frequently Marine Turtles stray far into the temperate zones, and it thus happens that one and the same species G3phargis coriαxeα) has been found on the south coast of England, near Cape Cod in North America, and on the coast of Chili. In short the geographical distribution of these Reptiles is that of pelagic animals generally, although by their mode of propagation they are compelled to sojourn near land during a certain period of the year.

2. The Sea-Snakes are restricted to, and highly characteristic of, the fauna of the tropical Indo-Pacific Ocean, and more especially of parts between Arabia and North Australia. They prefer the vicinity of laud, but never leave the water, with, perhaps, the single exception of Platums. Their distribution is not erratic; only one species, Pelamys bieolor, a Sea-Snake which more than any other is organized for a marine life, has spread far beyond the original home of its kindred, viz., westwards to the coasts of Madagascar and south-eastern Africa, and eastwards to the furthermost limits of the region, viz., to the coasts of central and northern South America.

All other Reptiles are terrestrial, and, as they are chiefly developed in the tropics, we begin our account with the regions of the equatorial zone. The scope of this article does not allow us to enter into an examination of the subregions which have been proposed by various authors.

1. The Indian Region.— Of the four principal groups of terrestrial Chelonians, the Emydidae and Trionycidae (Freshwater Tortoises and Freshwater Turtles) predominate over the Testudinidae, which are scarce and restricted, the fourth (Chelydidae) being absent altogether. We know fifty-seven species from this region :— [table]

Three of these genera are peculiar to the region, viz., Manouria, Platysternum, and Emyda. Characteristic is the scanty representation of Testudo. One species which is common in the Indian peninsula (2 ’ . stellata} is so similar to an African species as to have been considered identical with it; the Burmese Tortoise is also closely allied to it, and the two others extend far into western Central Asia. Thus this type is to be considered rather an immigrant from its present headquarters, Africa, than a survivor of the Indian Tertiary fauna, which comprised the most extraordinary forms of Land Tortoises. Wallace’s line marks the eastern boundary of Trionyx; species of this genus are common in Java and Borneo, and occur likewise in the Philippine Islands, but are not found in Celebes, Amboyna, or any of the other islands east of Wallace’s line.

Of Crocodilidae true Crocodiles are represented by four, and Gavials by two species. Alligators are absent.

Although the region is characterized by numerous highly specialized genera of Laceritilia, not one of the families is peculiar to it.

Agamidae are exceedingly numerous, and are represented chiefly by arboreal forms; terrestrial forms, like Aganιa and Urαmastix, inhabit the hot and sandy plains in the north-west, and pass uninterruptedly into the fauna of western Central Asia and Africa. The Geekonidae, Scincidae, and Varanûdae are likewise well represented, but without giving a characteristic feature to the region by special modification of the leading forms. The Laeeriidae are represented by one characteristic genus, Tachydromus,—Ophiops and Cabrita being more developed beyond the limits assigned to this region. Finally, the Eublepharidae and Anguidae, families whose living representatives are probably the scattered remains of once widely and more generally distributed types, have retained respectively two species in western India, and one in Khassia (Khasi Hills), whilst the presence of a single species of Chamaeleon in Southern India and Ceylon reminds us again of the relations of this part of the fauna to that of Africa.

The Indian region excels all the other equatorial regions in the great variety of generic types and number of species of Snakes. The latter amount to no less than four hundred and fifty, which is nearly one-third of the total number of species known. They are referable to about one hundred genera, of which the majority do not range beyond the limits of the region. Of higher groups (termed families for the sake of convenience), the Xenopeltidae, Rhinophulae, Oligodontidae, Xenodermidae, and Acrochordidae are peculiar to, and characteristic of, this fauna,—but not more so than a number of genera which will be mentioned presently.

Of Typhlopidae more than twenty species are known.

Of Tortrieidae, the genus Cylindrophis is spread over several of the subregions.

The Calamariidae are represented by a whole string of genera, of which thirteen are peculiar to the region. The most characteristic and geographically most important types are Calamaria, with twenty-four species, spread over the archipelago and the eastern parts of the continent, and Aspidura and Haplocercus, with four species, which are limited to Ceylon and southern India.

Species of those generalized forms which are termed CoronelliJae and Colubridae are likewise numerous (sixty-six species), and referable to seventeen genera, of which ten are limited to this region. In the north-western and northern parts the genus Zamenis, which is one of the most characteristic types of the warmer parts of the Europo-Asiatic fauna, is represented by six species.

Freshwater Snakes are abundant in genera,-species, and individuals. Of Tropidonοtus alone some forty very distinct species have been described, besides three others which are sufficiently differentiated to deserve generic separation. Of the so-called Homalopswlae all the genera, twelve in number, are peculiar, and the great development of these Snakes is, therefore, one of the most striking features of this region.

Besides two species of Psammophis allied to African forms, a distinct genus Psammodynastes has a wide range over the eastern parts of the continent and the archipelago.

Tree Snakes are represented by eight genera and twenty-six species, mostly characteristic forms.

DipsaAiilae are more numerous (eighteen species) than in the other equatorial regions.

Elachistod<rn and Hologcrrhιιm may be mentioned as remarkable types not found elsewhere, but with a very local distribution.

The development of Lycodonts India has in common with Africa; but the genera, six in number, are distinct.

Also the presence of gigantic Snakes of the genus Python is a feature which India shares with Africa.

Of Erycidae three species are Indian, Gongylophis and Cursoria being peculiar to the region.

Poisonous Snakes are numerous, the proportion to innocuous Snakes being as 1 :10. Out of forty-six species, only two belong to the family of true Vipers, and they are restricted to the Indian peninsula with Ceylon, one {Echis} being even specifically identical with the African species, and the other {Dabοia) having its only congener in the Mediterranean district. The remainder of the poisonous Snakes belong to the Elapidae and Crotalidae or Pit Vipers. The former are represented by six genera, of which no less than five are highly characteristic of the region, whilst the Cobras {Naja) are equally distributed over Africa. Of Pit Vipers five genera have been distinguished, the most characteristic being an arboreal form, Trimeresurus, with seventeen species. Also the other five genera are peculiar to India, with the exception of the genus Halys which is Central-Asiatic.

The relations of the Indian region to the others will be considered as we proceed with the accounts of those faunas. Japan, with regard to its Reptilian fauna as a whole, must be referred to this region. This is clearly shown by the presence of species of Ophites, Calloρhis, Trimeresurns, Tachydromus,—characteristically Indian forms, with which species of Clemmys, Trionyx, Gecko, Halys, and some Colubrines closely allied to Chinese or Central-Asiatic species are associated. The few Reptiles inhabiting the northern part of Japan are probably Palaearctic species.

2. The African Region.— Owing to its strictly continental character and diminished variety of physical features, this region is inhabited by a much smaller number of Reptiles than one might be led to expect from the large extent of its geographical area. There are but few small outlying islands, furnishing a small number of interesting additions to this fauna. Madagascar, indeed, would supply a considerable contingent of distinct forms, but it is questionable whether this large island should be united with the African region, as we shall see hereafter.

The African region is characterized by the development of three of the four principal divisions of terrestrial Chelonians, viz., Testudinidae, Chelydidae, and Tmonycidae; the Emydidae are absent, being represented by one species only, in the north-western corner of the region (Emys platyceps). The thirty-seven species are distributed thus :— [table]

The majority of the genera are peculiar, viz., Chersine, Pyxis, Cinyxis, Dumerilia, Sternothcnιs, Pelomedusa, and Cyeloderma; and no other region shows a similar development of Land Tortoises. This last type has not only diverged into four genera, but is also represented by several of those gigantic forms which survived into geologically recent times. In the African region they inhabited only the neighbouring oceanic islands, viz., the Aldabra group, Mauritius, and Rodriguez; out of the eight species, which have been recognized chiefly from their osseous remains, one only survives at the present day. Also in Madagascar fossil remains of gigantic species, which must have been contemporaries of Aepyornis, have been discovered by Grandidier; but on the continent no trace of these large creatures has been found hitherto. The Chelonians of the eastern and western halves of the continent do not essentially differ from each other, but Trionyx does not extend southwards beyond the tropic.

Of Croeodilidae, Crocodilus is represented by three or four species. Alligators are absent.

Of the families of Lizards inhabiting Africa the majority occur in the southern portion. Λgamidχ are numerous, and represented chiefly by terrestrial forms. The Gecko-nidae, Scincidae, Laeertidae, and Varanidae are likewise well represented; Eublepharidae by a single genus and species in West Africa. The presence of several genera of Amphisbaenidae, some of which are even identical with South-American, is highly suggestive. Gerrhosaumdae, Zonuridae, and Anelytropidae are peculiar to tropical Africa; but the most important feature of this Lacertilian fauna is the almost universal distribution of Chamaeleons in numerous and highly specialized species.

Leaving aside, for the present, the island of Madagascar, we estimate that the number of species of African Snakes does not exceed two hundred, which are referable to about seventy genera, of which no less than fifty do not range beyond the limits of the region. On the whole the east coast genera are different from those of the west coast, but in the southern parts no such differentiation can be shown. Very little is known as regards the range of the species and genera towards the central districts. As regards higher groups only two families, the Dasypeltidae and Dinophidae, are peculiar to Africa; and, although they have a wide range over the region, they consist of very few species only. Other families show a greater variety of genera and species here than in any other part of the globe. The almost entire absence of the genus Tropi-(lonotus and the scanty representation of Colubers are very noticeable features. Poisonous Snakes are numerous, all the various families being well represented, with the exception of the Pit Vipers; singularly enough innocuous Colubrine Snakes with facial pits occur {Bothrophthalmus, Bothrolycus).

Of Typhlopidae nearly forty species have been described, and, besides, the Stenostomatidae are represented by seven species.

Eight out of ten Calamaroid genera are peculiar to this fauna, and remarkable is the frequency with which among them the sub-caudal shields coalesce into a single series.

The Caronellidae are represented by some twenty species, but no true Coluber occurs, the four species which approach this type most closely belonging to distinct genera {Seaphiophis, Xenurophis, Herpetaethiops).

Almost entire absence of Tropidonotics is a characteristic feature of this fauna. Also of other Freshwater Snakes only six genera with seven species are known.

The small family of Psammophidae is well represented by three genera and nine species, of which six belong to Psammophis.

Of Tree-Snakes there are six genera, of which Ahaetulla (Philo-thamnus) is most generally distributed, in twelve species.

Of Dipsadidae there are five genera and ten species, four of which belong to Diρsas proper.

The Lycodonts are as well developed as in India, by seven genera and fourteen species; all the genera are peculiar to Africa, and some of them are modified for an arboreal mode of life.

Of Pythons three species are distinguishable; but, besides, a member of the Booid family (Pelophilus fordii) occurs on the west coast.

Two species of Eryx occur.

Poisonous Snakes are extremely numerous, the proportion to innocuous Snakes being as 1: 5. Of Elapidae four genera occur, among which Naja figures with at least two species; besides this family the Dinophidae are a remarkable and characteristic type, having assumed entirely the appearance and mode of life of Tree Snakes. The Atraetaspididae, with three genera and thirteen species, are likewise almost entirely African, only one other type CDinodipsas) having been recently discovered in Venezuela. Pit Vipers are absent, but the largest forms of Viperidae are developed in this region, this family being represented by four genera and twelve species. The singular genus Atheris is a real Tree Viper with prehensile tail.

The Reptilian fauna of Madagascar is a most remarkable mixture of types belonging to different regions, which cannot be accounted for in the present state of our knowledge of the geological changes that have taken place whilst the present fauna was already in existence.

The Chelonians offer a marked point of distinction from those of Africa: no Trionyx occurs in Madagascar. On the other hand species are found of Testudo, Chersine, Sternotherus, and Pelοmedusa, which are spread also over a greater or lesser area of the continent. Two Chelonians, Pyxis and Dumeriliα, are peculiar to Madagascar, the latter nearly allied to the South-American Peltoccphalus. The Madagascar Crocodile is closely allied to the common African species.; and its presence in the island can be easily accounted for.

Among the Lizards we find a distinctly South-American element in two Iguanoid genera, Hοplurus and Chalarodon, replacing the Old World Agamidae. The absence of Varanidae, Laeertidae, and Amphisbaenidae removes Madagascar from Africa, whilst the extraordinary development of Chamaeleonidae (more than twenty species) and the presence of Gerrhosauridae and Zouuridae are important features common to both. Avery small family (Uroplatidae} is peculiar to Madagascar. No special relation to the Indian region is shown by this Lacertilian fauna.

With regard to Ophidians, Madagascar has hardly anything in common with Africa. The African fauna is characterized by the great development of Lycodonts,—they are absent in Madagascar; and of the four families of African poisonous Snakes Madagascar does not possess a single one. When we analyse the affinities of the twenty-seven species known at present from Madagascar, we arrive at the following conclusions :—

1. Snakes without distinct relations to any particular region :— Tyρhlops (six species), Ablabes (one species), Ithyeyphus (one species), Dipsadoboa (one species).

2. Snakes with affinities to the African fauna :—Mimophis (one species), Pedophilus (one species).

3. Snakes with affinities to the Indian fauna :—Ptyas (one species), Langaha (one species).

4. Snakes with affinities to the South-American fauna :—Liophis (one species), Taehymenis (one species), Pseiidoxyrhopus (two species), Heterodon (two species), Dromieus (one species), Herpeto-dryas (one species), Philodryas (one species), Dipsas (two species), Xiphosoma (one species).

Africa shows affinities to all the three other equatorial regions, but chiefly to the Indian. No sharply defined boundary exists between the two regions, the intervening parts of Asia being inhabited by a desert fauna which penetrates into districts of similar nature in Africa as well as in India. Certain genera and species belonging to this desert fauna are therefore common to both regions. But there are, besides, other points of affinity of deeper significance, such as the development in both of a distinct Trionycoid genus, besides the typical Trionyx, the general distribution of Agamoids and Varanidae, the presence of the remarkable family of Lycodonts, which do not occur anywhere else, of the large forms of Python with concomitant absence of Booids, and of the Elapidae, of which one genus ( Naja ) extends from the west coast of Africa to Borneo. But these resemblances are fully counterbalanced by great differences in other portions of the Reptilian fauna: the Indian Emydoids are replaced by Chelydidae in Africa, a type which it has in common with Australia and South America, whereas India possesses no Amphisbaenidae, no Chamaeleons. With regard to Ophidians, the number of forms generally is greatly diminished in Africa, but the proportion of poisonous Snakes is doubled. The Pit Vipers of India are wholly absent, and are replaced by true Vipers. In the Indian region arboreal Agamoid Lizards prevail; in Africa the Snakes show a greater tendency towards a modification of the habitus and structure for arboreal life. The Freshwater Snakes and Colubers which are so numerous in India are much reduced in numbers in Africa, Tropidonoti being almost entirely absent.

3. The Tropical Pacific Region.— So far as Reptiles are concerned, Tasmania has to be included in this region. No Trionyx or Emys goes eastwards beyond Wallace’s hne. In fact, the Chelonian type disappears in the islands between this line and the Australian continent— with two exceptions. A species of Testudo (T. forstenii) occurs in, and is limited to, the island of Gilolo; and Cuora amboinensis, the most common Tortoise of Malaya, occurs in many of the eastern islands, but it has probably been imported by man, and by the same means may be still extending its range. On the continent of Australia Chelydidae only occur, viz., eight species of Chelemys and five of Chelodina. In Tasmania, again, Chelonians are absent.

Besides the common Indian Crοcodilus porosus, which may be considered an immigrant into this region, one or two other species of the same genus inhabit the fresh waters of the truly tropical parts, and are peculiar to Australia.

The bulk of the Lacertilian fauna is composed of Skinks, Geckos, Agamoids, and Varanidae, with the addition of a small family which is peculiar to the region, the Pygo∙ podidae. A peculiar type, Hibamus, has been found in New Guinea; and, finally, a single Iguanoid, Brachylophus, is common in the Fiji Islands; how it came there, or how it survived its severance from the American stock, is a mystery. The Skinks are in this region more highly developed and more specialized than in any other part of the world; they exceed in numbers the Geckos, which generally accompany the Skinks in their range over the smaller islands of the Pacific; in these islands members of these two families represent the whole of the Lacertilian fauna. The Australian Agamoids are chiefly peculiar and partly much differentiated forms, but some have distinct affinities to, or are even identical with, Indian genera. The Varanidae are also closely allied to Indian species.

The total number of Snakes amount to ninety species, of which twelve are Typhlops, eight other innocuous Colubrines, fifty Elapidae, one Erycine, fourteen Pythonidae, and five Boidae. The number of poisonous Snakes, therefore, exceeds that of innocuous, a proportion quite unparalleled in any other part of the world. The few innocuous Colubrine Snakes belong to Indian genera, and evidently have spread from that region; but all the genera of Elapidae (twelve), Erycidae (one), Pythonidae (five), and Boidae (three) are peculiar to this region.

In Australia we meet, therefore, with the interesting fact that, whilst it is closely allied to South America, but totally distinct from India, by its Chelonians, its Lizards and Colubrine Snakes connect it with this latter region. With regard to the other Ophidians, they, although peculiar genera, have their nearest allies partly in India partly in South America; and the character of the Australian Snake fauna consists chiefly in its peculiar composition, differing thereby more from the other equatorial regions than these do among themselves. Wallace’s line marks the boundary between India and Australia only as far as Chelonians are concerned, but it is quite effaced by the distribution of Lizards and Snakes. Thus in New Guinea Lizards of the Indian region are mixed with Pygopodidae, and an island as far east as Timorlaut is inhabited by six Snakes, three of which are peculiarly Indian, whilst the other three are as decidedly Australian. The islands north of New Guinea and of Melanesia are not yet occupied by the Ophidian type, and only species of Enygrus have penetrated eastwards as far as the Low Archipelago, whilst the Fiji Islands and the larger islands of Melanesia have sufficiently long been raised above the level of the sea to develop quite peculiar genera of Snakes. Tasmania is tenanted by poisonous Snakes only.

4. The Tropical American Region.— An examination of the distribution of Chelonians in the New World leads to a different division of its regions from that of the other Reptiles. Central America and the West Indies, with regard to Chelonians, cannot be united with the Southern continent, The Chelonians of South America proper are the following (forty-three species) :— [table]

The Chelydidae thus predominate to the exclusion of the Emydidae. They belong to five distinct genera, of which one, Chxlys, is the most specialized of the family. They do not extend to the western side of the Andes, and cease in the south with the system of the Plate River. Northwards they penetrate to Trinidad, but become scarcer in the degree in which their place is occupied by the Emydidae, which have spread from Central America over the northern parts of this region. One, Emys d ’ orbignii, following the course of the Uruguay, has penetrated southwards to the mouth of the Plate River.

Land Tortoises (Testudd) are at the present day almost extinct in this region, two species only (Τestudo tabulata or earbonaria and T. argentina) being found on the continent of South America. The six other species belong to the Oceanic Island Tortoises of gigantic size, and inhabit or inhabited the Galapagos group.

Trionyx is entirely absent.

The Crocodilian order is more developed in this region than in any other. Besides at least three species of Crocοdidus, six Alligators occur. The former occupy Central America, with Mexico, the coast of Florida, the West Indies, Ecuador, and the system of the Orinoco; the latter extend much farther southwards, throughout the system of the Plate River, whilst in North America this genus is represented by a distinct species, A. missis-sippensis. Alligators found in some of the West Indian islands are believed to be immigrants from the continent.

The Lacertilian fauna connects Central with South America,—all the six families found in the latter area, viz., Geckonidae, Anguidae, Ampldsbaenidae, Tejifilae, Igua-nidae, and Seincidae, being represented in Central America. But Central America possesses, besides, five other families, small in species and restricted in range (some belonging to the fauna of great elevations), but highly interesting types. These are the Eublepharidae, Xenosauridae, Aniel-lidae, Helodermatidae, and Lepidophymatidae. Their localization and differentiation can be accounted for on the hypothesis that they are the remains of the fauna of the various islands into which Central America was broken up at a former period.

By far the larger number of Lizards of the Tropical American region are Iguawidae, a family which in the New World repeats the Old-World Agamidae. They are spread over the whole of the region, having adapted themselves in their mode of life and structure to every variety of ground. One species (Liolaemus magellanicus) ranges to the Straits of Magellan. The largest Iguanoids inhabit the Galapagos Islands, where they live on the rocks of the shore, one species (Oreocephαlus cristatus) entering seawater and feeding on sea-weeds. The next numerous family is the Tejidae, the New-World representatives of the Old-World Laxertidae·, Ceekonidae, Seincidae, Amphisbaeuidae, and Anguidae are less numerous, but have also a wide range over the region. The Lacertilian fauna of the West Indies is wholly South-American; it does not comprise any peculiar family, and only a few characteristic genera, of which Anolis is, perhaps, the most highly specialized and the one which is composed of the greatest number of species; this genus, however, is also well represented on the continent, especially in Central America.

With regard to Ophidians the Tropical American region approaches the Indian in the number of species, which amounts to about four hundred, but it exhibits a comparatively less variety of generic and peculiar forms; of the eighty genera only about fifty do not range beyond its limits. However, a boundary line which would separate the Ophidian fauna of South America from that of the north does not exist. In Central America and

Mexico the generic types of the south and north are intermingled, and as the climate, in accordance with latitude and altitude, assumes a more temperate character the specifically tropical Snakes disappear and are in part replaced by those of North America. This mixture of the two faunae and the great variety of physical conditions within a small area account for the relatively very large number of Snakes of Central America. About one hundred and fifty out of the four hundred species attributed to the whole region belong to this district. The West-Indian Ophidians belong to the Tropical American fauna; many continental generic forms of the latter occur in the islands, and such genera as are peculiar to the West Indies do not exhibit a common feature, or are founded on slight characters. The exact limits to which Snakes extend southwards are not known; they seem to be very scarce on the southern confines of the Argentine Republic. Quite recently a Crotaline Snake, Rhinocerophis, has been discovered in eastern Patagonia.

Of families peculiar to or highly characteristic of this fauna we can mention one only, viz., the small family Scytalidae, which replaces the Lycodonts of the Old World. The Boidae are likewise a prominent feature, although not exclusively confined to South America; of eleven genera eight are Tropical American, and three Australian. The true Boas include the most gigantic of Snakes, and replace the Old-World Pythons.

In this fauna a peculiar and highly ornamental pattern of coloration, which consists of more or less regularly alternate rings of black, red, and yellow, seems to be the more worthy of notice, as it occurs in very distinct families, viz., the C alamarüdae, Coronellidae, Natrwidae, Leptognαth-idae, Scytalidae, Tortricidae, Elapidae.

Of Typhlopidae more than twenty species have been described, and, besides, the Stenostomatidae are represented by seven species.

Of Tortricidae one species occurs.

The Calamariidae are represented by thirteen genera, of which ten are peculiar. The most characteristic and geographically important are Elapomorρhus with ten, Hamalocranium with sixteen, Ninia with four species. The Indian genus Geoph⅛ is represented in Tropical America by twenty-five species.

Coronellidae are extremely numerous (sixty-six species referable to thirteen genera). Of these Xenodon with twelve species, Liο-phis with sixteen, Erythrοlαmρrus, and Pliocereτιs deserve special mention.

Of Colubers forms with elongate compressed body, approaching arboreal forms (Sqiilotes), are not scarce.

Freshwater Snakes are not abundant, but a genus peculiar to the region, Helieops, occurs in eight species. Tropidonotus might be regarded as absent, but for three or four species which occur north of the Isthmus of Panama and in the West Indies; also the allied genus Tretaηοrhinus is confined to Central America and the West Indies.

Tree Snakes are extremely abundant—some seventy species referable to six genera, of which Dromicus, Philodryas, and Herpetodryas are very characteristic forms. Of Ahaetulla some seventeen species are knoλvn.

Of Dipsas and allied genera only four species occur, but of tlιe peculiarly South-American Leptognathidae some twenty-five species have been distinguished.

In Central America there occur two extremely singular forms which, however, are imperfectly known and seem tobe restricted to a very limited area. One, Loxoeemus, is considered a representative of the family Pythonidae, and the other, Nοtοpsis, is stated to be the type of a distinct family allied to the Indian Xtmodermidae.

Of the twenty species of Boidae the West Indian contingent amounts to no less than eight or nine, a fact which clearly demonstrates the pertinence of the West Indies to this region.

Erycidae are absent.

Poisonous Snakes are numerous, the proportion to innocuous Snakes being as 1: 8. Besides the singular occurrence in Venezuela of a member of the Atraetaspididae, Dinodipsas, the Colubriform poisonous Snakes are represented by one genus only, Elaρs, which, however, shows numerous varieties or species, and is extremely common and widely spread over the region. Viperidae are absent; but the largest forms of Pit Vipers {Crotalidae) are developed in this region, and represented by five genera, which, if not peculiar to Tropical America, are at least confined to the New World, like Cenchris and Crotakus.

The Reptilian fauna of tropical America thus shows relations to the other equatorial regions in three of its constituent parts only, viz., in the Chelydidae, Amphis-baenidae, and Crotalidae. It has the former type in common with Africa and Australia; but, whilst the presence of Trionyx on the African continent forms an important distinctive feature, the resemblance of South America to Madagascar is as great as, or even greater than, that to Australia, which lacks Testudo.

On the other hand the Lacertilian fauna is essentially distinct from that of the Old World, with the exception of Amphisbaenidae (and of species of Eublepharidae), whose presence in South America and Africa is a most remarkable fact, and very strong evidence of the former existence of intervening land. The Skinks and Geckos, which are generally distributed over the warmer parts of the globe, cannot come into consideration.

The Snakes of Tropical America differ also much more from those of the Old-World regions than certain other portions of its fauna, as, for instance, its Batrachians and Freshwater Fishes. A distinct affinity with India is expressed only by the development of the family of Pit Vipers,—the presence in both regions of numerous Tree Snakes, of species of the genus Geophis, of the family Tortricidae, Ac., being less significant points of resemblance. But these resemblances are more than counterbalanced by the absence in South America of Lycodonts, Tropidoηoti, Pythonidae, Erycidae. The African Ophidian fauna is still further removed by Crotalidae being entirely wanting and replaced by Viperidae ; only a few genera, like Steηo-stoma, Coronxlla, Leptodira, Dipsas, Ahaetulla, are examples in which species are found in both regions. In both Tropidonotus is almost absent.

As all the innocuous Colubrine Snakes of Australia are derived from the Indian region, they form no part in a comparison between the Australian and South-American faunae. Of the other Ophidian types these regions have not a single genus in common, nor a family which would not be represented also either in Africa or India or both.

5. The North-American Region.— While the Chelonians of the North-American or Nearctic region (in which, so far as this Reptilian order is concerned, Central America and the West Indies have to be included) are essentially different from those of South America, the Lizards and Snakes of both belong to the same family types, and pass in an unbroken series from the northern to the southern parts of the New World.

In this region the Emydidae have attained to as great a development as in the Indian, and are associated with a few representatives of Testudo and Trionyx. The species, which are altogether about fifty in number, and of which a few are common to the Central-American and North-American sections, are distributed as follows :—

Testudo.................

Central America, including Mexico.

......... 0

N. America.

1

r Cistudo....................

.......... 1

1

Clemmys................

......... 13

10

Dermatemys............

.......... 1

0

Macroclemmvs..........

.......... 0

1

ι Chelydra.................

......... 2

1

Staurotypus.............

......... 3

0

Aromochelys............

......... 0

2

''Cinosternurn............

.......... 10

3

Trionyx..................

......... 0

2

30

21

It may be seen from this list that no Chelydoid passes northward beyond the Isthmus of Panama; the Chelonians of Central America belong exclusively to the Emydidae, which are represented by some thirty species; the majority do not extend either into South or North America; two of the genera, Dermatemys and Staurotypus are peculiar to it, and Cinosternurn has its headquarters in this section. Neither Trionyx nor Testudo occurs. Proceeding beyond the Mexican boundary, we find still the Emydidae predominating, a few of the species of Central America ranging northwards into the United States; distinct species of Clemmys, Cinosternurn, Chelydra, he., appear, with the wonderful genus Maeroclemrnys. An instance of the isolated occurrence of a Testudο ( T. polyphemus) is met with here; and from the lower part of the Mississippi northward one of the most characteristic features of the North-American fauna makes .its appearance, viz., two species of Trionyx, of which one at least follows the ramifications of that river northward and has found its way into Lake Winnipeg (51° N. lat. ). West of the Rocky Mountains Tortoises are scarce and of distinct species.

In the West Indies the following species have been found :— 1, Testudo tabulata; 2, Podocnemis dumeriliana; 3, Emys continua; 4, E. decussata; 5, E. rugosa. Of these the first two are identical with South-American, and the third with a North-American species, and, therefore, may be regarded as strangers which in comparatively recent times have been introduced into the West Indies. On the other hand the last two are species peculiar to the islands, and, as they belong to a North-American generic type, clearly prove the pertinence of this island district to the northern continent, so far as Tortoises are concerned.

The south-eastern parts of North America are inhabited by an Alligator which is specifically distinct and locally separated from the southern species.

The tropical Lacertilian and Ophidian faunae gradually merge into that of the temperate north, and any boundary line drawn between the north and south is more or less arbitrary. As a matter of fact so many truly tropical forms advance north of the tropic of Cancer (which by many authors is taken as the boundary line) that we are inclined to restrict the limits of this region to the district about the Rio Grande, whilst, on the other hand, the northern fauna extends to a lower latitude on the plateau of Mexico. Thus restricted, the North-American fauna includes about fifty species of Lizards, belonging to genera which with very few exceptions are already represented in Central America, or even farther southwards. By far the greatest number are Iguanidae; the Scincwlae, Anguidae, and Tejidae are represented by several, the Geckonidae by fewer species, whilst single species occur of the Amphisbaenidae, Aniellidae, Lepidophymidae, and Helοder-matidae,— all Central-American types. In fact, North America does not possess one family of Lizards peculiar to it.

11 is worthy of notice that Lizards do not extend so far northwards in the western as in the eastern hemisphere; one species (Gerrhonotus coeruleus) ranges into British Columbia, another into Minnesota CEumeces septeηtrioηalis), and a third into Massachusetts CFumeces fasciatτιs).

Of Snakes about one hundred species could be enumerated, with a proportion of 1 :14 of poisonous to innocuous Snakes. All the families represented in this fauna occur also in tropical America, and there is a great agreement of the genera with those of the Central-American district, so that less than one-half can be considered as peculiar to this region, viz., Cοnocephalus, Carρlιophis, Contia, Cemophora, Hypsiglena, Chersodramus, Rhiηxchilus, Pituοphis, Ischnognathus, Clιαriηa, Wenona, Lichanura. Calamariidae and a much larger number of “North-American” terrestrial Chelonians is given, viz., forty-three. This is partly due to the southern boundary of “North America” being extended to the tropic of Cancer, partly to the fact that species are admitted in a different sense from those of the herpetologists of the Old World. By adopting these species a very erroneous impression would be created as regards the comparative numbers of the groups in the several regions. That check-list includes three species of Testudο, three of Cistudo, twenty-one of Emys and its subgenera, five of Cinosternurn, two of Αronιοchelys, one each of Mαcroclemrnys and Chelydra, and six of Trionyx.

Coronellidae are numerous; so are Colubers, of which Pituopbis is the most characteristic. Freshwater Snakes abound, especially of the genus Tropidonotus. Of Tortricidae three genera have been distinguished. No true Vipers occur, but Pit Vipers are represented by three genera, of which two are Rattlesnakes.

After what has been stated already, the affinities of this to other regions can be summed up in a few words. The Reptilian fauna of North and South America forms, with the exception of the Chelonians, a homogeneous whole by which the Neogean division proposed by Sclater for Passerine Birds is well characterized. On the other hand, the Chelonian fauna of North America is entirely distinct from that of South America, and most closely allied to that of India.

6. The Europa-Asiatic Region.— Whilst the north of the western hemisphere has at least one order of Reptiles, the Chelonians, by which it is distinguished from the south, the temperate region of the eastern hemisphere possesses no important distinguishing type of Reptile. Its Reptilian fauna is merely an offshoot of those of the two adjoining tropical regions; and, if we were to add the genera most characteristic of the Palaearctic fauna to either Africa or India, the character of neither would be modified or changed. Thus, so far as Reptiles are concerned, a Palaearctic region does not deserve to rank with the other primary regions.

The Chelonians are represented by nine species only, viz. :—

Testudo, ....................................................4 species

Emys, .......................................................3 ,,

Trionyx, ....................................................2 ,,

—types which are only specifically distinct from those of the two southern tropical regions. The Land Tortoises are confined to the warmer districts of the western portion, penetrating into the centre of the Siberian sub-region, and entirely absent in the northern and eastern parts; of Emys one species CE. lutaria) is still found in north-eastern Germany as far north as 54° N. lat. ; and probably some other species will be found in similar latitudes in the little explored Amur country, where also a species of Trionyx ( T. maaekii) occurs. The second species of this latter genus which is referable to this region inhabits the Euphrates and Tigris.

The recent discovery of an Alligator in central China is a highly interesting fact, but not surprising, when we remember the occurrence in China of not a few North-American types of Batrachians and Freshwater Fishes. The common African Crocodile still lingers in the Mediterranean district,—its presence in Syria having been placed beyond doubt, and its occurrence in Sicily having been asserted on very good authority.

The Lacertilians include the only family type which this region has not derived from either Africa or India, viz., the Anguidae. Two genera of this family, Anguis and Pseudopus, are widely spread in Europe, and closely allied, the former to the South-American Ophiodes, and the latter to the North-American Ophiosaurus. Laeertidae are abundant as in Africa, and Amphisbaenidae and Chamaeleontidae represented at least in the Mediterranean district. Towards the central parts of Asia the terrestrial Agamidae are continued from north-western Africa, partly with but slight modifications, Phrynoeefihalus being a specifically Central-Asiatic genus. In the Manchurian sub-region these African types are replaced by some Indian forms, such as Gecko and Taehydromus. The northern range of Lizards in this region extends as far as Lapland (Lacerta υivipara and Anguis fragilis).

The most characteristic Ophidian genus of the region is Zamenis, a Colubrine form which is very widely spread, and includes more species (eleven) than any other Palaearctic genus. This genus extends over Arabia, and even into the island of Socotra, without being associated there so far as is known at present with Snakes of an either peculiarly African or Indian type. The total number of Palaearctic Snakes amounts to sixty, of which twelve are poisonous Snakes, viz., nine Vipérines and three Halys. The majority inhabit the Mediterranean district and western Asia.

Four Typhlops and a single Stxnοstoma have been found in the Mediterranean district and Persia.

Of the small number of Calamariidae and Coronellidae. Rhyncho∙

calamus, Psilοsomα, Lytorlιyηchus, and Ditypophis (Socotra) are genera not found beyond this region.

Colubridae are comparatively numerous, and show less affinity to African than Indian forms. Besides Zamenis, Coluber and Elaphis occur in four species each, and Rhineehis and Acontiophis (Afghanistan) are peculiar genera.

Three or four species of Tropidcrnotus represent the groups of Freshwater Snakes.

The Psammophidae are well developed; besides two species of Psammophis, Taρhrometopοη and Coelopeltis are peculiar genera, but not extending into eastern Asia.

There is one species of Eryx.

One species of Naja reaches the Caspian.

The three species of Halys are Central-Asiatic.

Of the nine species of Vipérines six belong to Vipera and Cerastes. Dαboia and Εchis may be considered to have their headquarters in this region, but they extend into southern India, and Eehis has spread east and west along the barren plains or deserts of North Africa and north-western India.

7. Hew Zealand.— The southernmost parts of South America, Africa, and Australia are not inhabited by a sufficiently differentiated fauna to be separated from the tropical regions of which they are the continuation. None of the small oceanic islands south of 40° or Tierra del Fuego possess any Reptiles. On the other hand New Zealand is by the possession of Hatteria, the sole living remnant of the extinct order Rhynehoeephalia (not to mention other scarcely less important parts of its fauna), so much distinguished from the other regions that it cannot be associated with any of them. Although the climate and other physical conditions seem to be well adapted for the existence of the Chelonian and Ophidian types, neither is represented; and of Lizards only representatives of the ubiquitous Skinks and Geckos have reached its shores; but some of the latter must have inhabited New Zealand for a long period, as they belong to a distinct genus, Naultinus, which is peculiar to this group of islands.

At the conclusion of this section it will be useful first to recapitulate the principal features of the Reptilian faunae for each of the primary regions into which the land of the globe has been divided by zoologists, and which nearly coincide with the geographical divisions, and secondly to arrange the regions according to the natural relations as expressed by this class of animals. A division into zones comprising the corresponding parts of both hemispheres cannot be maintained for Reptiles, since the greater portion of the faunae of the temperate are merely the offshoots of tropical faunae, no peculiar types of a higher than generic rank being developed in them.

1. The Indian Region is characterized by Trionyeidae and Emydidae, but few Testudinulae. Croeodilidae, with Gavials. Lacertilians and Ophidians very numerous. Agamidae chiefly arboreal (Draco), and Varanidae. Pythonidae and Lyeodontidae. Ground Snakes, Colubers, Tree Snakes, and Freshwater Snakes abundant in genera. Tropidonotus. Poisonous Snakes in the proportion of species as 1: 10, and comprising Crotalidae and Elapidae, but only two Viperidae.

2. The African Region (exclusive of Madagascar) is characterized by Land Tortoises, Trionyeidae, and Chelydidae. Species of Croeodi∙ lus only. Lacertilians and Ophidians rather numerous. Agamûdae chiefly terrestrial; Laeertidae and Varanidae are well represented. Amphisbaenidae, Gerrhosauridae, and ZonuriAae are peculiar to the region. Chamaeleontidae. Pythonidae and Lyeodontidae. True Colubers and Tropidonotus almost absent. Psammophidae. Poisonous Snakes in the proportion of 1: 5, comprising Viperidae and numerous venomous Colubrines.

3. The Evroγo-Asiatic Region is composed of a mixture of Indian and African generic and family types; and only a few peculiar genera have their centre of distribution in this part, such as Anguis, Pseudopus, Ρhryηoccphalus, Uromastyx, Stxnοdaetyhιs, Also-phylax, Cerαmodaxtylus, Scineus, Zamenis, Coelopeltis, Taphrοnιeto-pon, Daboia, Eehis, Halys. The majority inhabit the sub-tropical and warmer parts abutting upon the neighbouring tropical regions, and are rapidly reduced in number in the more temperate portion.

4. The Tropical Pacific Region possesses one of the terrestrial Chelonian types, Chelydidae, and species of Crοeοdilus only.

Besides Skinks and Geckos, terrestrial Agamidae and Varanidae are well represented; Pygopodidae. EryeiJlae, Rythonidae, and Boidae are autochthonous, whilst a small number of innocuous Colubriues are immigrants from the East Indies. The poisonous Snakes surpass in number the non-poisonous, and belong to the Elapidae.

5. Madagascar possesses Chelydidae and Testudinidae without Trionyx, like South America. A species of Crocodile. Chamae-leontidae more differentiated here than in Africa, with which it has also Cerrhosauridae and Zonuridae in common; Agamidae are replaced by the South-American Iguanidae. Snakes chiefly South-American; no poisonous Snake.

6. The Tropical American Region is characterized by the full development of Testudinidae and Chelydidae and absence of Trionyx; Emydoids are immigrants from the north. Crocodiles and Alligators. Lacertilians numerous in families and species, the majority being Iguanidae; the Old-World Lacertidae replaced by Tejidae. Other families, Angiddae, Amq)hisbaenidoe, Eiiblepharidae, Helodermatidae, &c., well represented. Snakes numerous: Boidae and Scytalidae; Ground Snakes, Colubers, and Tree Snakes abundant, less so Freshwater Snakes; Tropidonotus almost absent. Poisonous Snakes in the proportion of species as 1: 8, and comprising Crotalidae and Elaps.

7. The North-American Region differs from the Tropical in possessing the Emydidae in their full development and Trionyx; only one Testudo. One Alligator. As regards Lacertilians and Ophidians this region occupies the same relation to tropical South America as the Palaearctic region does to Africa and India.

8. New Zealand is characterized by the possession of the Rhynchocephalian type, without any other Reptile with the exception of certain Skinks and Geckos.

Arranging these primary divisions of the globe in accordance with the distribution of the several orders of Reptiles, we find that with regard to Chelonians the regions stand in the following relation to each other :—

I. Emydidae fully developed.

A. Trionycidae fully developed.

1. Testudinidae in small numbers or immigrants: a. Indian-Palaearetic regions, and b. North-American region (including Central America).

IL Chelydidae fully developed.

A. Trionycidae fully developed.

1. Testudinidae fully developed: African region.

B. Trionycidae absent.

1. Testudinidae fully developed: α. Tropical American region, and b. Madagascar.

2. Testudinidae absent: Tropical Pacific region.

III. Chelonians entirely absent: New Zealand

The types of Crocodilian and Rhynchocephalian orders are too few in number and either very widely or very locally distributed, so that no general division of the globe’s surface can be based upon them alone.

The two large Lacertilian families Geckonidae and Scirtcidae are generally distributed over the warmer parts of the globe, and therefore not well adapted for the distinction of the primary regions. Nevertheless, in a more detailed account many of the genera would have to come into consideration, being confined to more or less limited areas. Both families are represented in great variety in Australia, but scantily in South America. With regard to other families the regions can be arranged thus :—

I. Agamidae and Varanidae fully developed.

A. Chamaeleontidae, Lacertidae, and Amphisbaenidae: African region (including as sub-region the Western Palaearctic portion, characterized by Anguidae).

B. Amphisbaenidae and Chamaeleons (except one species)

absent; Lacertidae few: Indian region with Manchurian sub-region.

C. Pygopodidae: Tropical Pacific region.

IL Iguanidae fully developed.

A. Chamaeleontidae: Madagascar.

B. Tejidae, Amphisbaenidae, and Anguidae: Sοutlc-American and North-American regions.

III. Skinks and Geckos only: New Zealand.

Of the families of Ophidians the Pythonidae and Boidae, the Crotalidae and Vipemdae, the Lycodontidae and Scytalidae replace each other in their distribution, and are, therefore, best adapted for determining the relations of the zoological regions. Although the first two are so far as we know at present the geologically oldest types, and therefore might be employed in the first instance in the arrangement of the regions, their distribution is limited to the equatorial zone, and fails to show the close relations existing between the temperate and equatorial parts of the Old World on the one hand and those of the New on the other. The relations of Madagascar to Tropical America are in the following scheme less distinctly expressed than they are in nature.

I. Viperidae fully developed.

A. Pythonidae and Lycodontidae: African region.

B. Tropidonoti and true Colubers: western portion of the

Europo-Asiatic region.

IL Crotalidae fully developed.

A. Pythonidae and Lycodontidae in the tropical parts;

Tropidonoti and true Colubers; none of the Crotalines with rattles: Indian region (including Manchuria).

B. Tropidonoti and true Colubers; some of the Crotalines with rattles; intermediate between the Manchurian sub-region and tropical America: North-American region.

C. Boidae and Scytalidae: Trop)ixal-American region

III. Colubrine venomous Snakes only.

A. Pythonidae and Boidae: Tropical Pacific region.

IV. Venomous Snakes entirely absent.

A. Boidae: Madagascar.

V. Snakes entirely absent: New Zealand. (A. Ç. G. )