MAMMALIA. 321 
from the sides and connecting the fore and hind limbs, 
which enables them to leap great distances, the membrane 
acting as a parachute, held out by the limbs, and bony, 
boom-like appendages attached to them. 
The marmots are represented in this country by the 
prairie-dog (Fig. 
347). They in- ul 2 
habit the plains of ; : NA ‘) 
the West. The fur ai fy 
is reddish brown, 
and lighter be- 
neath. They live 
in burrows in com- 
munities, and utter 
a sharp chirp re- 
sembling a bark. 
The  burrowing- that live in its burrow. 
owls and’ rattle- 
snakes live with them, the latter probably preying upon 
the young of both. 
The woodchuck is common in North America, attain- 
ing a large size. Their fur is a grizzly color. 
VALUE.—Six million squirrel-skins are used yearly by the trade. 
The hairs of the tail are made into delicate paint-brushes. 
Beavers (Castoride).—The beavers are represented in 
America by one species. They are characterized by a 
broad, flattened, scaled tail, that is used as a scull in 
locomotion. They have five toes upon each foot, those 
upon the hinder ones being webbed. They are aquatic 
in their habits, living upon the bark of trees and other vege- 
tation, or meat, when domesticated. They are famed for 
their industry and intelligence in the construction of their 
homes.* The young, from two to eight, are produced in 
* The beavers show great intelligence in making their habitations. 
As it is necessary that the house should be under water, a smal] stream 
