These fossil bones ,_ found in successive geologic formations of the Age of Mammals, sfto:v 

 graphically the evolution of the horse. In the centre, 'skulls; at the left,' hind feet; at the right, 

 forefeet. The horse whose skull is shown at the bottom was the size of a fox terrier. It had 

 four complete toes in fore foot, three in hind fcot; middle toe a little larger than side toes. 

 The Oligocene horse was the size of a sheep; three toes complete and reaching the ground, but 

 middle toe enlarged; outer toe of the fore foot reduced to a short splint. The Miocene horse 

 was the size of a Shetland pony; side toes complete but slender, and did not reach the ground 

 in walking. The Pliocene horse was the size of a donkey; side toes complete but did not reach 

 the ground. The Pleistocene horse was the size of our domesticated horse; side toes reduced to 

 splints as in all the living species. At this point the race became extinct in America. The 

 modern horse, shown at the top, is probably bred from wild races which inhabited Asia, 

 Europe, and Northern Africa in prehistoric times. 



