134 Zoological Society, 



ones are also traversed by an internal longitudinal groove, but 

 this is so deep and wide, that it divides the vi^hole 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 Toxodon, 

 the dentigerous Brutu, 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 jmirs 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 Rcgne 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. 



CLASSIFICATION OF THE MARSUPIALIA. 



Tribes. Families. Genera. Subgenera. 



Sarcophaga. 



Three kinds of teeth; 



canines long in both f Thylacinus. 



jaws ; a simple sto- Dasyuridee. . ■< Dasyurus. 



mach ; no intesiinum L Phascogale. 



ctecum. 



, . f Phascolotherium. "I „ •! 



Extmcttransitional forms \ Thylacotherium. / ^°''''- 



Entomophaga. 



Three kinds of teeth in 



both jaws ; a simple j^i^iatoria. . Myrmecobius. 

 stomach ; a moderately 



long intestmum cacum. 



„ J. ^ . fChaeropus. 



Saltatorta. . jp.ratneles. 



Scansoria. . Didelphis. . . . Cheironectes. 



