70 NATURAL HISTORY. 
being needed only for crushing ; in 
the Rat they are raised into points, 
he being carnivorous; while in the 
. , herbivorous Rodents they are real 
grinders, as represented in Fig. 54. 
116. The bushiness of the tail is 
: the peculiar characteristic of the 
Fig. 64.—skull ot Kodent Squirrel family. ‘This, when spread 
nimal. ° : : 
out, is of some assistance in the leap- 
ing of these arboreal animals, both guiding and buoying 
them up. In the Flying Squirrel, Fig. 55, there is an ar- 
rangement similar to 
that of the Flying 
Lemur, § 57. 
117. The Ameri- 
can Marmot, or 
W oodchuck, as it is 
commonly called, is 
about the size of a 
rabbit. It has an 
underground _habi- 
tation, divided into 
apartments, and 
lives on clover and 
esculent vegetables. Like some of the Monkeys (§ 52), 
it has cheek pouches, in which it carries stores of food to 
its burrow. 
118. The Mouse and Rat family is the most numerous 
of all the families of the Mammalia, and contains the 
smallest animals. Of the common Mouse, Cuvier says, 
“it is known in all times and in all places.” Ofthe Rats 
there are two principal species, the Black Rat, and the 
Brown or Brownish-gray. The Black Rat is called the 
old English Rat, which was introduced into England from 
France as late as the sixteenth century. This is now 
nearly exterminated by the Brown Rat, which is a stron- 
ger animal. This latter Rat was introduced into this 
Fig. 55.—Flying Squirrel. 
