1895.] NATURAL, SCIENCES OF PHILADELPHIA. 261 



perished from the cold. This seems probable from their high 

 northern range, and the immense store of their remains now existing 

 in northern Siberia, and in the ice-bound Liakhow or New Siberian 

 Islands. A similiar fate may have overtaken the Irish elk, the 

 urus, the mastodon, and other animals, but such was certainty not 

 the case with the American horse, nor with the giant sloths and the 

 glvptodon of South America, animals which became extinct during 

 the same period. 



The disappearance of the horse, in America, is an unsolved mys- 

 tery. This animal extended in range through a double continent, 

 and has left its remains from Alaska to Patagonia. The horse, it is 

 true, is one of the most highly specialized of animals, and thus be- 

 longs to the class that is most liable to sudden extinction. But its 

 specialization is not one that confines it within narrow or local limits 

 or to a temporary phase of conditions. It is at home on the firm, 

 grassy uplands, and is unsuited to forest, mountain, or moist low- 

 lands. In the eastern hemisphere the natural habitat of the horse 

 is on the steppes of Asia, while other species of the genus inhabit 

 the plains of southern Asia and of Africa. In the western hemi- 

 sphere it was probably most abundant on the open plains of 

 central and western North America, and on the great grassy plains 

 of the southern continent. As regards the habitat of the North 

 American horse, it is one that is exposed to snows, frequently severe 

 ones, in the winter season. The same may have been the case in 

 Asia, if the habit of scraping with the fore- feet, which is possessed by 

 the horse, arose, as has been supposed, from an instinct of scraping 

 away the snows to get at the herbage beneath. Despite this instinct, 

 in abnormal winters, many horses must have perished through the 

 depth and persistance of the snows, as many cattle and sheep do now. 

 During the glacial period this condition existed in an exaggerated 

 degree, and may have caused the extinction of the North American 

 horse. Most of its original range was buried under mountains of 

 ice, which persisted for many centuries. South of the ice limit very 

 frigid conditions must have existed, and deep and persistant snows 

 each winter probably covered all the southern regions of the United 

 States and the plateau of Mexico. 



Under such conditions the horse might well have become extinct. 

 Many contemporaries, such as the bison, the antelope, etc., could 

 have taken refuge in the forest and swampy regions of the semi- 



