Myriapods have been usually divided into the two orders Ckilognatfιa or Millepedes and Chiloρoda or Centipedes; but recently a small myriapod, ∙ 5 ⅛th of an inch in length, was discovered by Sir J. Lubbock, among decomposing vegetable matter, differing from the other members of the class in the absence of tracheae, apparently absorbing air through its semi-transparent skin, in the smaller number of its legs (nine pairs), and in the bifid character of its antennae; and this has been made the type of a third order— Pauropidae. Pauropus Huxleyi Lubbock describes as an active, cleanly little creature, with a look of cheerful intelligence, in marked contrast to the dull stupidity of the Julidoe, or the melancholy ferocity of the centipede. Millepedes, or “Thousand-Legs,” are readily distinguished from the other group by their antennae, which are always six or seven jointed, by the generally cylindrical shape of the body, and by the possession of two pairs of legs on each segment—the last posterior segments and a few anterior excepted. Each segment also bears a pair of stigmata or tracheal openings, instead of every alternate one, as in centipedes; and this fact, taken in connection with the double quantity of legs, has led to the belief that each segment in the millepede has been formed by the union of two, a view further strengthened by the presence of a distinct transverse groove down the centre of each. The legs of millepedes though numerous are exceedingly weak, and in moving they appear to glide along like footless worms. They are most frequently found among damp moss, and beneath masses of decaying vegetable matter on which they feed; and when in danger they roll themselves into a ball. The British species are few, and the largest of these does not exceed 2 inches in length; but there is an American form which attains a length of 8 inches, All are equally harmless, the prehensile jaws being rudimentary, while the other parts of the mouth are modified to suit their purely vegetable diet.

Centipedes, or “Hundred-Legs,” have their segments flattened, and covered with a leathery skin, and have one pair of legs on each segment, the posterior pair being directed backwards and elongated so as to resemble a couple of jointed tails. Their antennae have not less than fourteen and rarely more than forty joints, while the body segments do not usually exceed twenty. The organs of the mouth are masticatory, and are admirably adapted to the carnivorous habits of the centipede. It feeds principally on insects, seizing them with its powerful prehensile organs, and injecting at the same time its venom into the wound. The bite of the larger forms, as Scolopendra morsitαns, occurring in tropical countries, is exceedingly painful, and is described by those who have suffered from it “as similar to what might be produced by contact with a red-hot iron,” giving rise to swelling, throbbing pains, and febrile symptoms (Dr Collingwood’s Naturalist’s Rambles in the China Seas). These, however, yield readily to an application of ammonia. Centipedes seldom exceed a foot in length. They are exceedingly active in pursuit of their prey, insinuating their many-jointed and flattened bodies under stones, beneath the bark of trees, and wherever insects usually lurk. Lithobius forcipatus, the commonest British species, is 2 inches long, and quite harmless, although when seized it attempts to fix its jaws into the skin of its captor. The species belonging to the genus Geophilus are said to be luminous in the dark. Upwards of twenty species of fossil Myriapoda are known,— the oldest from the Coal Measures of North America, and belonging to the millepede or vegetable-eating division. One of these, Xylobius sigillaria, was found in the hollow trunks of the fossil Sigillaria.