DISTRIBUTION OF ANIMALS IN AMERICA. 243 



is confined to the extinction of many Pachydcrmata, a 

 displacement of the rhinoceros, elephant, tapir, and hip- 

 popotamus, and an extremely abundant development of 

 the true ruminants and the cattle which proceeded from 

 them with an exaggerated form of head. Bears and 

 canine species occupy the territory where viverridae and 

 hyenas once predominated ; but as " numerous locally 

 and historically limited species, a large number — among 

 the smaller fauna a majority — of Miocene races remain in 

 possession of the ancient and probably constantly increas- 

 ing habitat." (R.) " In this gradual change of things, 

 no one will be able to discern aught but phenomena of 

 the same order of which we are still the witnesses." (R.) 

 How circumstances occurred in America has been 

 described in a masterly style by Riitimeyer as follows: 

 " America affords a basis for the distribution of animals 

 completely different from that of the Old World. In 

 the latter, ridges, open only in places, divide the entire 

 continent into mountainous zones, and correspond to 

 the distribution of temperature. Thus in a twofold 

 manner they prescribe a definite range east and west 

 to the extension of animals; while a migration from 

 north to south is impeded less by the height of the 

 mountains than that on their summit the north comes 

 into contact with the scorching south. Behind this wall, 

 moreover, in the expanse from the Caspian Sea to China, 

 there is a zone of steppes and deserts which fences in 

 the animals more effectually than the mountain chains. 

 In America, not beasts of prey alone, but graminivora 

 also, may advance without hindrance from the regions 

 of the lichen on the Mackenzie River, through the pine 

 forests of Lake Superior, to the land of the magnolia 



