. Annals of natural history. Natural history; Botany; Zoology; Geology. 134 Zoological Society, ones are also traversed by an internal longitudinal groove, but this is so deep and wide, that it divides the whole tooth into two prismatic portions, with one of the angles directed inwards. The inferior molares are in like manner divided into two trihedral portions, but the intervening groove is here external, and one of the faces of each prism is turned inwards. All the grinders are curved, and de- scribe about a quarter of a circle; in the upper jaw the concavity of the curve is directed outward
. Annals of natural history. Natural history; Botany; Zoology; Geology. 134 Zoological Society, ones are also traversed by an internal longitudinal groove, but this is so deep and wide, that it divides the whole tooth into two prismatic portions, with one of the angles directed inwards. The inferior molares are in like manner divided into two trihedral portions, but the intervening groove is here external, and one of the faces of each prism is turned inwards. All the grinders are curved, and de- scribe about a quarter of a circle; in the upper jaw the concavity of the curve is directed outwards, in the lower jaw inwards. The false and true molares like the incisors have persistent pulps, and are consequently devoid of true fangs: in which respect the Wombat differs from all other Marsupials, and resembles the extinct Toa;odon, the dentigerous Bt^uta, and herbivorous Rodentia. Although none of the Marsupialia possess teeth composed of an intermixture of layers of ivory, cement and enamel through the body of the crown; yet the layer of cement which covers the enameled crown is thickest in the vegetable-feeding Marsupials, and is re- markably distinct in the Wombat. I may add that the Wombat deviates from the other Marsupials in the number of its ribs : as these are very constant in the rest of the order, the difference in the Wombat, which has 15 pairs, in- stead of 13 or 12, is the more deserving of notice. The Koala, like the Phalangers and Kangaroos, has 13 pairs of ribs. Professor Owen next proceeds to compare the classification of the Marsupialia here proposed with that of Cuvier, given in the second edition of the Regne Animal; and states the reasons which have led him to devise a new arrangement. The following is a tabular view of Professor Owen's classifica- tion. Sarcophaga. Three kinds of teeth;. Entomophaga. Three kinds of teeth in both jaws ; a simple ^^^j^^^,,,-^, . stomach; a moderately long intesiinum ccecum. Scansoria. Didelphis. . Pleas
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