BRANCH CHORD AT A: CLASS MAMMALIA 39 J 



brown rat (Mus decumanus) was introduced into this 

 country from Europe about 1775, and has now nearly 

 wholly supplanted the black rat (M. rattus), also a 

 European species, introduced about 1 544. The beaver 

 (Castor canadensis) is the largest rodent. It seems to be 

 doomed to extermination through the relentless hunting 

 of it for its fur. The woodchuck or ground-hog (Arctomys 

 monax} is another familiar rodent larger than most mem- 

 bers of the order. The chipmunks and ground-squirrrels 

 are commonly known rodents found all over the country. 

 They are the terrestrial members of the squirrel family, 

 the best known arboreal members of which are the red 

 squirrel (Sciurus hudsonicus), the fox-squirrrel (S. ludo- 

 vicianus), and the gray or black squirrel (S. carolinensis). 

 The little flying squirrel (Sciuropterus volans] is abundant 

 in the Eastern States. 



The shrews and moles (Insectivora). The shrews 

 and moles are all small carnivorous animals, which, 

 because of their size, confine their attacks chiefly to insects. 

 The shrews are small and mouse -like; certain kinds of 

 them lead a semi-aquatic life. There are nearly a score 

 of species in North America. Of the moles, of which there 

 are but few species, the common mole (Scalops aqitaticui) 

 is well known, while the star-nosed mole (Condylura 

 cristatd) is recognizable by the peculiar rosette of about 

 twenty cartilaginous rays at the tip of its snout. Moles 

 live underground and have the fore feet wide and shovel- 

 like for digging. The European hedgehogs are members 

 of this order. 



The bats (Chiroptera). The bats (fig. 153), order Chi- 

 roptera, difTer from all other mammals in having the fore 

 limbs modified for flight by the elongation of the forearms 

 and especially of four of the fingers, all of which are con- 

 nected by a thin leathery membrane which includes also 

 the hind feet and usually the tail. Bats are chiefly noc- 



