THE BISON. 611 
others as a musk sheep (Ovidos priscus Ritimeyer). If this 
is the case the musk sheep, or a species closely allied to it, 
formerly extended to the Middle States at or near the close 
of the glacial period. 
We now come to the bison and ox. The American bison 
Fig. 530.—Rocky Mountain Sheep or Big-Horn.—From Brehm’s Thierleben. 
(Bison Americanus Gmelin) formerly ranged from Virginia 
and Lake Champlain to Florida, and westward from the 
northern limit of trees to the Rocky Mountains and eastern 
Mexico. It is nowin danger of extermination, being mainly 
restricted to a few herds on the plains. It is closely 
