192 NEW YORK ZOOLOGICAL SOCIETY. 
sideration the white bear, which is circumpolar in its distribution, 
and is assigned to a separate subgenus, Thalarctos, we can place 
all the American bears in one of these three groups. 
THE BLACK BEAR GROUP. 
Judging from the degree of type divergence and from distri- 
bution, the first of these bears to arrive in North America was the 
black bear group, U. americanus. Its variation from the true 
Ursus is of subgeneric value, and the members of the group are 
assigned to the subgenus Ewarctos. This group we find distrib- 
uted throughout the length and breadth of North America to the 
limit of tree growth in the North and West, with a subspecies, U. 
sornborgeri, in Labrador, and species in Florida, U. foridanus, 
in Louisiana, U. luteolus, a recently described bear of large size 
from Queen Charlotte Island, U. carlottae, and most distinct of 
all, the blue or glacier bear, U. emmonsi, with a limited distribu- 
tion in Alaska, in the district of the St. Elias Alps, and east- 
ward among the rugged coast ranges as far as Juneau. 
In South America a closely related form, the spectacled bear, 
U. ornatus, has followed the Peruvian Andes south of the equa- 
tor. It is sometimes assigned to a subgenus, Termarctos, but is 
very closely related to the typical black bear, U. americanus. 
As the black bear only extends into Mexico there is a long 
break in the distribution of the genus, where bears have appar- 
ently died out. So that we need not be surprised to find that this 
isolated South American form is somewhat aberrant. This bear 
is, furthermore, the sole representative of the family in the 
southern hemisphere. 
Titsis quite evident from the distribution of the group that its 
residence in America is of considerable antiquity. 
THE GRIZZLY GROUP. 
All these black bears differ from the European bears more 
than do the grizzlies. From this fact, and from the distribution 
of the grizzlies along the range of the Rockies, we can safely be- 
lieve that they are later arrivals from Eurasia than are the black 
bears. 
The grizzlies have not evolved any well-marked species except 
perhaps the Barren Ground grizzly of the far North, U. richard- 
soni, about which very little is known. 
