240 ANIMAL STUDIES 



The opossums, fairly abundant throughout the warmer 

 portions of this country, are rat-like creatures, with scaly 

 tails, yellowish-white fur, large head, and pointed snout. 

 Except at the breeding season they lead solitary lives, 

 sleeping in the holes of trees by day and at night feeding 

 on roots, birds, and fruits. 



The kangaroos, familiar from specimens in menageries 

 or museums, chiefly inhabit the plains of Australia. The 

 giant gray kangaroos (Macropus giganteus), attaining a 

 height of over six feet, go in herds, and owing to the great 

 development of their hind limbs and tails are able, when 

 alarmed, to travel with the swiftness of a horse. Several 

 smaller species, some no larger than rabbits, live among 

 the brush, and like their larger relatives crop the grass and 

 tender herbage with sharp incisor teeth. 



While the marsupials do not lay eggs as does the duck- 

 mole, they allow them to develop within the body for a 

 very short time only. Hence the young, when born, are 

 scarcely more than an inch in length, and are blind, naked, 

 and perfectly helpless. At once they are placed by the 

 mother in the pouch of skin, or marsupium, on the under 

 side of her body. In this the young are suckled and pro- 

 tected until able to gather their own food and fight their 

 own way. 



224. Rodents or gnawers (Glires). The rodents are a 

 large group of mammals, including such forms as the rats, 

 mice, squirrels, gophers, and rabbits. They are readily dis- 

 tinguished by their clawed feet adapted for climbing or 

 burrowing, and by large curved incisor teeth. Unlike 

 ordinary teeth, they grow continually, and, owing to the 

 restriction of the hard enamel to their front surfaces, wear 

 away behind faster than in front, thus producing a chisel- 

 like cutting edge. 



The largest of our native rodents is the porcupine 

 (EretJiizon dorsatus), which ranges from Maine to Mexico, 

 and attains a length of nearly three feet. Many of the hairs 



