THE FORERUNNERS OF THE HORSE 243 



Kent not only was the Himalaya non-existent, 

 but that along the line of its very heart — where the 

 kiang now lives at an elevation of from thirteen 

 thousand to sixteen thousand feet — extended an 

 arm of the sea of no inconsiderable depth. 



Although one of the earliest forerunners of the 

 horse-tribe, the above-mentioned Hyracotherium, 

 lived in England during the deposition of the 

 Lower Eocene London Clay, the evolution of the 

 Equidce is much more clearly displayed in the 

 Tertiary strata of North America than it is in those 

 of Europe, where the chain is completely broken 

 during the Oligocene epoch. From this it has 

 been inferred that the entire evolution took place 

 on the American continent ; althoush as mentioned 

 in an earlier chapter, the real birthplace was pro- 

 bably in East Central Asia, whence the group 

 spread in one direction into Europe, and finally 

 Africa, and in the other into North America, and 

 thence, during the late Pliocene epoch, when the 

 two continents became united, into the southern 

 half of the New World. 



In both North and South America members 

 of the horse-family survived into the Pleistocene 

 epoch ; those of the northern continent belonging 

 to the existing Equus, whereas those of the southern 

 continent represented extinct generic types. In 

 North America the whole group died completely 

 out at the close of the Pleistocene ; and it is 



