Mammalia. 257 



The duckbill has a horny bill similar to that of a duck. 

 Its habits are similar to those of a muskrat. It lives in 

 water, and has holes in the bank, which it can enter beneath 

 the water. The body is about as big as a cat's, though 

 it presents a " squatty " appearance, the legs being very 

 short. The feet are webbed and the tail is flattened. It is 

 covered by a soft, fine fur. The duckbill has rudiments of 

 teeth in the early stages of its life, but in the adult state 

 neither the duckbill nor the spiny ant-eater has any teeth. 



The ant-eater is of about the same size as the duckbill. 

 The hairs are developed into strong, stiff, sharp spines. 

 The bill is conical, and a small mouth at the end permits 

 the extension of the slender tongue, with which it licks up 

 ants like other ant eaters. It lives in rocky ground. 



SUBCLASS II. THERIA. 



The Theria include all the remaining mammals. In this 

 subclass the young are born alive, in the form of the adult. 



The Marsupials. Our only marsupial is the opossum. 

 This odd animal is well known, at least by report, on 

 account of its habit of feigning death when attacked. The 

 marsupials get the name from their most marked charac- 

 teristic, the possession of a pouch, or infolding of the skin 

 of the abdomen. Two peculiar bones extend forward from 

 the pelvis, toward the pouch ; they are called the mar- 

 supial bones, as they support the pouch. The young are 

 born in a very immature condition, and are transferred to 

 the pouch, where they are nursed. The young are kept a 

 long time developing in the pouch, and, after they become 

 self-helpful, occasionally take refuge in the pouch. The 

 opossum is almost omnivorous, eating insects, eggs, and 

 birds, the teeth being of the carnivorous type. The opossum 

 is a good climber, and has a hairless, scaly, prehensile tail. 



