508 



THE VERTEBRATE SKELETON. 



fourth metacarpals are attached to the upper part of the third 

 metacarpal. In Hipparion 1 and other early horse-like animals 

 the second and fourth digits, though very small and function- 

 less, are complete and are terminated by small hoofs. In Rhi- 

 noceros the second and fourth digits are equally developed 

 and nearly as large as the third, and reach the ground in 



JT 



FIG. 106. MANUS OF PERISSODACTYLES. 



A. LEFT MANUS OF Tapirus. (After VON ZITTEL.) 



B. EIGHT MANUS OF Titanotherium. (After MARSH.) 



G. LEFT MANUS OF Chalicotherium gigantium. (After GERVAIS.) 



scaphoid. 



lunar. 



cuneiform. 



trapezoid. 



magnum. 



6. unciform. 



7. trapezium. 



II, III, IV, V. second, third, 

 fourth and fifth digits. 



walking, a vestige of the fifth is also present. In the -Tapir 



1 See 0. C. Marsh, various papers including "Fossil horses in 

 America," Amer. Natural. 1874 ; " Polydactyl horses," Amer. J. Sci. 1879 

 and 1892. M. Pavlow, "Le de>eloppement des Equides," Bui. Soc. 

 Moscou, 1887, and subsequent papers in the same. Osborn and Wortman, 

 " On the Perissodactyls of the White Eiver beds," Bull. Amer. Mus. Dec. 

 23rd, 1895. 



