8 EVOLUTION OF THE HORSE 
locality is on the Niobrara river in Nebraska, another in central 
Oregon. Many separate teeth and bones have been found in the 
phosphate mines near Charlestown, S. C.; other specimens have 
come from central Florida, from southern Texas, Arizona, Kan- 
sas, Louisiana and even from Alaska. They are, in fact, so 
often found in deposits of rivers and lakes of the latest geological 
epoch (the Pleistocene) that the formation in the western United 
States has received the name of Equus Beds. 
In South America, in strata of the Pleistocene Epoch, there 
occurs, besides several extinct species of the genus Equus, the 
Hippidium, a peculiar kind of Horse characterized by very short 
legs and feet, and some peculiarities about the muzzle and the 
grinding teeth. The legs were hardly as long as those of a cow, 
while the head was as large as that of a racehorse or other small 
breed of the Domestic Horse. 
All these horses became extinct, both in North and South 
America. Why, we do not know. It may have been that they 
were unable to stand the cold of the winters, probably longer 
continued and much more severe during the Ice Age than now. 
It is very probable that man — the early tribes of prehistoric 
hunters — played a large part in extinguishing the race. The 
eompetition with the bison and the antelope, which had recently 
migrated to America — may have made it more difficult than 
formerly for the American Horse to get a living. Or, finally, 
some unknown disease or prolonged season of drought may have 
exterminated the race. Whatever the cause, the Horse had dis- 
appeared from the New World when the white man invaded it 
(unless a few individuals still lingered on the remote plains of 
South America), and in his place the bison had come and spread 
over the prairies of the North. 
In Central Asia, two wild races persist to the present day; 
others were domesticated by man in the earliest times, and their 
use in Chaldea and Egypt for draught and riding is depicted in 
the ancient mural paintings. In Africa the larger species became 
extinct in prehistoric times, as in America, but the smaller zebras 
still survive in the southern part of the continent (one species, 
the Quagga, abundant fifty years ago, is now probably extinct), 
and the African Wild Ass is found in the fauna of the northern 
