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Show 134 MAMMALIA. or less yellowish brown. It is found in King's Island to the south of New Holland, where it lives in its burrow. Its flesh excellent. ( 1) ORDER V. RODENTIA. We have just seen, in the Phalangers, canini so very small, that we cannot consider them as such. The nutriment of these animals, accordingly, is chiefly derived from the vegetable kingdom. Their intestines are long and their crecum ample; and the Kanguroos, which have no canini whatever, subsist upon vegetables only. The Phascolomys might stand first in that series of animals of which we are about to speak, and which have a system of mastication still less complete. Two large incisors in each jaw, separated from the molars by an empty space, cannot seize a living prey nor tear flesh; they cannot even cut the food, but they serve to file, and by continued labour, to reduce it into separate molecules, in a word, to gnaw it; hence the term Rodentia or Gnawers, which is applied to animals of this order. It is thus that they successfully attack the hardest substances, frequently feeding on wood and the bark of trees. The more easily to accom· plish this object, the incisors have no thick enamel except in front, so that their posterior edges wearing away faster than the . anterior, they are always naturally sloped. Their pris· matlc form causes them to grow from the root as fast as they wear away at the edge ; and this tendency to increase in (1) .111. Bass has described an animal, externally similar to the Phascolomys, and to w~chbe also gives the name of Wombat, but which has six incisors, two canines and stxteen m 1 · h · d ·rr 0 ars m eac Jaw. If there is no erroneous combination of the two 1,u erent d. e scr·t p tio ns, 1· t W·ln form an additional subgenus to place near the Pera· u;,eles. lllJger has already established it under the name of .!lmblotis, from 11.p.~Aoorru1, aA ortus. See Petersb. Mem. 1803-1806, p. 444, and the Bulletin des Sc. No. 72, n. XI. RODENTIA. 135 length is so powerful, that if one of them be lost or broken its antagonist in the other jaw having nothing to oppose 0; comminute, becomes developed to a most monstrous extent. The lower jaw is articulated by a longitudinal condyle, in such a way as to all~w of no hor.izontal ~otion, except from back to front, and vzce versa, as IS requisite for the action of gnawing. The molars also have flat crowns, whose enamelled eminences are always transverse, so as to be in opposition to t~e horfzontal motion of the jaw, and to increase the power of trituratiOn. The genera in which these eminences are simple lines and th.e cro':n is very ~at, are more exclusively frugivorous~ those m whiCh the emmences of the teeth are divided into blunt tubercles are omnivorous; while the small number of such as have no points more readily attack other animals and . ' approximate somewhat to the Carnaria. The form of the body in the Rodentia is generally such that the hinder parts of it exceed those of the front; so tha~ ~ey.rather leap than walk. In some of them this disproportion Is ~ven ~s excessive as it is in the Kanguroos. . The mtestmes of the Rodentia are very long; their stomach Simple, or but little divided; and their crecum very voluminous, even more so than the stomach. In the subgenus Myoxus, however, this intestine is wanting. .In the whole of this class the brain is almost smooth and Without furrows; the orbits are not separated from the temporal fossre, which have but little depth, and the eyes are altogether directed laterally. The zygomatic arches thin and curved belo w, announce t h e weakness of the J·a Ws; ' the fore- ~rms have nearly lost the power of rotation, and their two ones. are often united; in a word, the inferiority of these aniTmha ls 1s • 'bl · VISI e m most of the details of their organization. ose ?enera however which possess stronger clavicles have :certa1? degree of dexterity, and use their fore feet to coney their food to the mouth. Some of them even climb with facility: such is the |
