BRANCH CHORD AT A: CLASS MAMMALIA 3 8 9 



in Australia and Tasmania; the Edentata, including the 

 sloths, armadillos, and ant-eaters found in tropical regions ; 

 and the Sirenia, including the marine manatees and 

 dugongs, are not represented (except by a single man- 

 atee) in North America. In the following paragraphs 

 some of the more familiar mammals representing each of 

 the eight orders represented in North America are 

 referred to. 



The opossums (Marsupialia). The opossum {DiJct- 

 phys Virginia no) is the only North American representa- 

 tive of the order Marsupialia, the other members of which 

 are limited exclusively to Australia and certain neighbor- 

 ing islands. The kangaroos are the best known of 

 the foreign marsupials. After birth the young are trans- 

 ferred to an external pouch, the marsupium, on the 

 ventral surface of the mother, in which they are carried 

 about and fed. The opossum lives in trees, is about the 

 size of a common cat, and has a dirty-yellowish woolly 

 fur. Its tail is long and scaly, like a rat's. Its food 

 consists chiefly of insects, although small reptiles, birds, 

 and bird's eggs are eaten. When ready to bear young 

 the opossum makes a nest of dried grass in the hollow of 

 a tree, and produces about thirteen very small (half an 

 inch long) helpless creatures. These are then placed by 

 the mother in her pouch. Here they remain until two 

 months or more after birth. Probably all the North 

 American opossums found from New York to California 

 and especially common in the Southern States belong to 

 a single species, but there is much variety among the 

 individuals. 



The rodents or gnawers (Glires). The rabbits, porcu- 

 pines, gophers, chipmunks, beavers, squirrels, and rats 

 and mice compose the largest order among the mammals. 

 They are called the rodents or gnawers (Glires) because 

 of their well-known gnawing powers and proclivities. 



