EVIDENCES OF EVOLUTION 27 



ample of those horses that became extinct 

 during the Miocene, leaving no descendants, 

 and Anchitherium, found both in Europe and 

 in America, was probably also on a side 

 branch. Of the Miocene period, Dr. Lull 

 says: "This was a time of continental eleva- 

 tion and great expansion of our western 

 prairies and a consequent diminution of the 

 forest-clad areas." Many forms very per- 

 fectly adapted to soft herbage became ex- 

 tinct, "but the great majority were more 

 plastic and in consequence underwent a 

 remarkable development, during this period 

 reaching the culmination in numbers and 

 kinds." 



In the Pliocene there was a wide repre- 

 sentation of the Old World genus Hipparion, 

 most of the species still three-toed. It was 

 probably derived from the American Neo- 

 hipparion, a swift, deer-like animal, about 

 forty inches in height at the shoulder. "In 

 the Siwalik beds of India is found a one-toed 

 Hipparion, and it has been suggested that 

 the modern zebras may be the living descend- 

 ants of this genus. It is certainly not in the 

 line to the common horse, Equus caballus, 

 which makes its appearance, however, in the 

 Upper Pliocene beds both of Eurasia and 

 North America the climax of a long evo- 

 lutionary progression." 



