THE ANCESTORS OF THE HORSE 



are born with two complete little toes provided 

 with hoofs and attached to the splint-bones, 

 one on each side of the big central toe, " throw- 

 ing back," as the term is, to their three-toed 

 ancestors. Beyond the stage, with four equal 

 toes on the front foot and three on the hind- 

 foot, which is exhibited by a quite small horse- 



FiG. 94. — The skeleton of Hyracotherimn, an ancestor of 

 the modern horse, found in Eocene strata. 



like creature — the Hyracotherium shown in 

 Eigs. 94 and 95 — we can trace the pedigree of 

 the horse to a five-toed ancestor, the Phenacodus 

 (Eig. 96). The later stages of this history, from 

 the Mesohippus to the modern horse, have been 

 traced by very abundant fossil remains of many 

 steps or stages in the gradual change. Not only 



139 



