276 



UNGULATA 



respects a great contrast to such decadent types as those represented 

 by the Tapirs and Rhinoceroses. 



The principal anatomical characters by which the Artiodactyles 

 are distinguished from the Perissodactyles are as follows. The 

 premolar and molar teeth usually not alike, the former being 

 single and the latter two-lobed. The last lower molar of both first 

 and second dentition almost invariably three-lobed ; and the first 

 tooth of the upper cheek series always Avithout a milk-predecessor. 

 Xasal bones not expanded posteriorly. No alisphenoid canal. 



W M 



B 



p IG- 99.— Bones of right forefoot of existing Artiodactyles. A, Pig (Sus scrofa), xj; B, 

 Red Deer (Cervus elaphus), xi ; C, Camel (Camelus bactrianus), x£. U, Ulna; R, radius; c, 

 cuneiform; I, lunar; s, scaphoid ; u, unciform ; m, magnum ; td, trapezoid ; tm, trapezium. 

 From Flower's Osteology of Mammalia. 



Dorsal and lumbar vertebras together always nineteen, though the 

 former may vary from twelve to fifteen. Femur without third 

 trochanter. Third and fourth digits of both feet almost equally 

 developed, and their ungual phalanges flattened on their inner or 

 contiguous surfaces, so that each is not symmetrical in itself, but 

 when the two are placed together they form a figure symmetrically 

 disposed to a line drawn between them. Or, in other words, the 

 ;».\is or median line of the whole foot is a line drawn between the 

 third and fourth digits, Avhile in the Perissodactyles it is a line 

 drawn down the centre of the third digit. Distal articular surface 



