DISTRIBUTION OF ANIMALS IN AMERICA. 243 
is confined to the extinction of many Pachydermata, a 
displacement of the rhinoceros, elephant, tapir, and 
hippopotamus, 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 viverridz 
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 corres- 
pond 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 migra- 
tion 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 
