CLASSIFICATORY SCIENCES. 635 



Pecora ; the Pachyderms include some of the Bruta and the Belluce, 

 comprehending also extinct animals, as Anoplotherium and Palceothe- 



But the two orders of Hoofed Animals, the Pachyderms and the 

 Ruminants, form a group which is held by Mr. Owen to admit of a 

 better separation, on the ground of a character already pointed out by 

 Cuvier ; namely, as to whether they are two-toed or three-toed. 

 According to this view, the Horse is connected with the Tapir, the 

 Palaeotherium, and the Rhinoceros, not only by his teeth, but by his 

 feet, for he has really three digits. And Cuvier notices that in the 

 two-toed or even-toed Pachyderms, the astragalus bone has its face 

 divided into two equal parts by a ridge ; while in the uneven-toed 

 pachyderms it has a narrow cuboid face. Mr. Owen has adopted this 

 division of Pachyderms and Ruminants, giving the names artiodactyla 

 and perissodactyla to the two groups ; the former including the Ox, 

 Hog, Peccary, Hippopotamus, &c. ; the latter comprehending the Horse, 

 Tapir, Rhinoceros, Hyrax, &c. And thus the Ruminants take their 

 place as a subordinate group of the great natural even-toed Division 

 of the Hoofed Section of Mammals ; and the Horse is widely separated 

 from them, inasmuch as he belongs to the odd-toed division. 8 



As we have seen, these modern classifications are so constructed as 

 to include extinct as well as living species of animals ; and indeed the 

 species which have been discovered in a fossil state have tended to fill 

 up the gaps in the series of zoological forms which had marred the 

 systems of modern zoologists. This has been the case with the divi- 

 sion of which we are speaking. 



Mr. Owen had established two genera of extinct Herbivorous Ani- 

 mals, on the strength of fossil remains brought from South America : 

 Toxodon, and Nesodon. In a recent communication to the Royal 

 Society 3 he has considered the bearing of these genera upon the divi- 

 sions of odd-toed and even-toed animals. He had already been led to 

 the opinion that the three sections, Proboscidea, Perissodactyla, and 

 Artiodactyla, formed a natural division of Ungulata ; and he is now 

 led to think that this division implies another group, " a distinct divi- 

 sion of the Ungulata, of equal value, if not with the Perissodactyla 

 and Artiodactyla, at least with the Proboscidea." This group he pro- 

 poses to call Toxodonta. 



Owen, Odontography. * Phil. Trans,, 1853. 



