392 



CLASSIFICATION OF VERTEBRATES. 



always lacking, digits with broad, blunt nails or more usually 

 with hoofs ; digits ranging from five to one, radius and ulna free 

 or united; scaphoid and lunar bones (p. 177) of carpus always 

 free. 



If only the living forms were considered the characters of 

 the ungulates and the sub-divisions of the order could be easily 

 given, but the fossil forms, which are especially well developed 

 in our western states, have introduced so many annectent 

 groups that boundary lines tend to disappear, while to almost 

 every character exceptions occur. Were the recent forms alone 



considered the order 

 would contain only the 

 artiodactyls and perisso- 

 dactyls of the following 

 pages, but the extinct 

 species connect these 

 so closely with the ele- 

 phants and Hyrax that 

 all must be included un- 

 der a common heading. 

 The existing forms are 

 all terrestrial and with 

 few exceptions herbivor- 

 ous, none being dis- 

 tinctly predaceous. For 



convenience all of these forms may be divided into the true 

 ungulates (Ungulata Vera or Diplarthra) and the Subungulata, 

 the former including the artiodactyls and the perissodactyls, the 

 latter the other sub-orders : Condylarthra, Amblypoda, Probos- 

 cidia, Toxodontia, and Hyracoida. 



In the Ungulata Vera the feet are never plantigrade ; the 

 digits never exceed four, the first being suppressed ; the molars 

 are quadritubercular. The mammae are abdominal or inguinal 

 in position, and are usually few in number. The placenta is 

 nondeciduate, and is either diffuse or cotyledonary. 



In the Subungulata the feet are frequently five-toed, and 

 they may be plantigrade, and the bones of the first row of the 

 carpus and tarsus -are in a direct row with those of the second, 



FIG. 363. Types of carpal bones ; A, in series 

 {taxeopodous) ; B, interlocking (diplarthrous). 

 R, radius ; U, ulna ; c, carpales ; /', intermedium ; 

 r, radiale ; u, ulnare ; 1-5, metacarpals. 



