506 THE VERTEBRATE SKELETON. 



rows of three each. Five digits are generally present, but 

 sometimes as in Balaenoptera musculus, there are four, the 

 third being suppressed. Their relative development varies 

 much. The Sperm Whale which till recently was placed in the 

 entrance hall of the Natural History Museum at South Ken- 

 sington has one phalanx to the first digit, four to the second, 

 five to the third, four to the fourth, and three to the fifth. 

 Generally the manus is short and broad, but sometimes, as in 

 Globicephalus, it is much elongated owing to the great develop- 

 ment of the second and third digits. 



UNGULATA 1 . The manus of the members of this great 

 order is of very great classificatory and morphological impor- 

 tance. All the members agree in having the scaphoid and 

 lunar distinct, and in almost every case the ends of the digits 

 are either encased in hoofs or provided with broad flat nails. 

 It is by means of characters derived from the manus and pes 

 that the group is subdivided into the Ungulata vera and 

 the Subungulata. 



In the UNGULATA VERA the manus is never plantigrade, 

 and there are not more than four digits, the pollex being almost 

 always completely suppressed : in Cotylops among extinct Artio- 

 dactyla however a vestigial pollex is found. The centrale is 

 absent, and the magnum articulates freely with the scaphoid, 

 and is separated from the cuneiform by the unciform and lunar. 

 A1J the bones of the carpus interlock strongly, and the axis of 

 the third digit passes through the magnum and between the 

 scaphoid and lunar. 



There is a very strong distinction between the manus of 

 the suborders Artiodactyla and Perissodactyla. In the Artio- 

 dactyla the axis of the manus passes between the third and 

 fourth digits, which are almost equally developed arid, except in 

 the Hippopotami and some extinct forms such as Anoplotherium, 



1 See E. Cope, " The origin of the foot structures of Ungulata," Journ. 

 ofPhilad. Acad. 1874. H. F. Osborn, "The evolution of the Ungulate 

 foot," T. Amer. Phil. Soc. 1889. 



