330 



EVOLUTION OF THE HORSE. 



to have been an odd-toed animal ; for one of these digits was 

 off the ground, and was consequently functionless. 



The foot of the rhinoceros {see Fig. 197) shows a marked 

 tendency to become one-toed. Being three-toed on its fore, 

 as well as on its hind feet, it belongs to a less ancient type 

 than the tapir. The Acerotherium {see Fig. 198) was a pro- 

 bable ancestor of the rhinoceros, if not of the horse. The 

 Brontotherium, which has been found in the Miocene of 





Fig. 196.— Hyracotherium (Jth real height). 



Colorado, had, similar to the tapir, four digits on its front 

 feet ; and three on its hind ones {see Figs. 199 and 200), 



Proceeding still further down in our search, we find in the 

 early Eocene, the Phenacodus pidmcsvus, which is supposed to 

 have been the ancestor, or one of the very early ancestors, of 

 all hoofed animals. Fi«g. 201 shows how it appears in a fossil 

 condition. It was about twenty-one inches high. From the 

 form of the third phalanx of its digits, we may conclude that 

 each of them carried a hoof. We may also see that each 



