274 



UNGULATA 



The more generalised of the fossil forms do not conform in all 

 respects to the above-mentioned characters ; clavicles being present 

 in Ti/potherium, and perhaps in some of the Condylarthra, while in 

 the latter group the humerus may have an entepicondylar foramen, 

 and thus approximate to the corresponding bone of the Carnivora. 

 Wide as is the gap between existing Carnivores and Ungulates, there 

 are indeed more or less strongly marked evidences of affinity 

 between the earlier members of the two orders, as will be again 

 noticed under the head of the suborder Condylarthra. A departure 

 from the normal type of foot^structure is exhibited by the extinct 

 Macrotherium, provisionally included in the Perissodactyla, where 

 the digits terminated in long and curved claws. 



As a general rule, the cheek-teeth have distinct roots, and in 

 those of the existing suborders a gradual increase in the height of 

 the crowns of these teeth may be noticed in passing from the more 

 generalised to the more specialised types. Those teeth in which 

 the crowns are low, and their whole structure visible from the 

 grinding surface, are termed brachydont (Fig. 122) ; while those with 

 higher crowns, in which the bases of the infoldings of enamel are 

 invisible from the grinding surface, are known as hypsodont (Fig. 123). 

 Again, when the tubercles on the crowns of the molars are more or 



less cone-like in form the tooth 

 is said to be bunodont ; but when 

 they are expanded in an antero- 

 posterior direction and curved into 

 a crescent shape the tooth is 

 described as selenodont. 



The whole order may be 

 divided into the Ungulata Yera, 

 containing the suborders Perisso- 

 dactyla and Artiodactyla, and a 

 somewhat heterogeneous assem- 

 blage of animals which may be 

 called Subungulata or Ungulata 

 Polydactyla. Cope has pointed 

 out a character in the structure 

 of the carpus by which the latter 

 are differentiated from the former. 

 Thus in all the Subungulata the 

 bones of the proximal and distal 

 row retain the primitive or more 

 typical relation to each other (see 

 Fig. 98) ; the os magnum of the 

 second row articulating mainly 

 with the lunar of the first, or 

 with the cuneiform, but not with the scaphoid. But in the group to 



B 



FIG. 98. Right fore foot of Indian Ele- 

 phant. X J. U, ulna ; R, radius ; c, cunei- 

 form ; I, lunar ; sc, scaphoid ; u, unciform ; 

 m, magnum ; td, trapezoid ; tm, trapezium ; 

 I to V, first to fifth digit. 



