MAMMALS. 103 



The monotreines include the duckbill and the spiny 

 ant-eaters. The duckbill is an aquatic animal, and re- 

 ceives its common name from the fact that it has a horny 

 bill much like that of the duck. It lives in burrows in the 

 banks of streams, and feeds on beetles, shrimps, etc., which 

 it catches in the water and crushes with its horny teeth, its 

 true teeth being lost at an early age. The spiny ant-eaters 

 resemble the duckbill in their burrowing habits, but they 

 live exclusively on the land, where they feed on ants. 

 They are, like the true ant-eaters (p. 106), entirely toothless, 

 and receive the adjective spiny of their common name from 

 the fact that their hair takes the shape of long stout spines, 

 recalling those of the porcupines. 



SUBCLASS II. MARSUPIALIA. 



This subclass receives its name from the fact that in the 

 female a curious pouch or marsupium is developed on the 



FIG. 39. Pelvis of Opossum. (After FIG. 40.- Opossum (Diclelphys vir- 

 Minot.) M, marsupial bone; ii, mniana). After Audubon and 

 ilium ; is, ischium ; p, pubis. Bachman. 



lower surface of the body of the female, in which the young 

 are placed by the mother immediately after birth, and where 

 they remain until able to take care of themselves. This 



