182 R. S. Lull — The Evolution of the Horse Family. 



Equus, the modern horse, first appears in the Upper Plio- 

 cene beds of Eurasia and North America, and represents the 

 culmination of the race. The feet are one-toed hut with well- 

 developed splints of the second and fourth digits still remain- 

 ing. These are sometimes fused with the adjoining canon 

 bone ; sometimes they are free, but only in the rare cases of 

 reversion do they bear any traces of the lateral toes. The 

 teeth are long columnar structures of intricate enamel pattern, 

 admirably suited to their owner's needs, while the animal has 

 attained tie maximum stature consistent with fleetness. 



Fossil members of this genus are very widespread, yet the 

 existing species are entirely confined to Asia ancl Africa. In 

 JSTorth America many fossil species have been described, 

 though reduced to nine by Gridley ; in point of tooth structure, 

 One of these, Equus fraternus, resembles closely the modern 

 horse, E. caballus. E. giganteus from southwestern Texas 

 was evidently of great size, " the teeth exceeding those of the 

 largest modern draught horses by more than one-third the 

 diameter of the latter " (Gidley). 



In spite of perfection of adaptation the American horses 

 became entirely extinct before the discovery of America 

 by Europeans. This is all the more remarkable in view 

 of the fact that conditions in our West are such that the 

 few horses which escaped from the Spanish explorers have 

 increased so marvelously in numbers, evidently finding these 

 conditions much to their liking. Long before domestication 

 the horse was hunted for food. Professor Osborn states that 

 " one of the bone heaps of the Solutreen period is estimated to 

 include the remains of over 80,000 horses." Even this great 

 slaughter would not be sufficient to cause extinction, for before 

 the invention of fire-arms not one race of large mammals suc- 

 cumbed to the lords of creation. 



Paleontological Laboratory, 

 Yale University Museum, 



February 12, 1907. 



