370 SYSTEMATIC ZOOLOGY. 



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. 374), 

 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. 



CLASS II. EUTHERIA. 



This division contains the great majority of the mam- 

 mals and is characterized by the following features : The 

 alimentary canal opens to the exterior distinct from the 

 reproductive and excretory organs, the sutures of the 

 skull are well marked and the coracoid bone is reduced 

 and fused with the shoulder-blade, forming the coracoid 

 process of human anatomy. The Eutheria are divided 

 into twelve orders: Marsupialia, Edentata, Rodentia, 

 Insectivora, Chiroptera, Cetacea, Sirenia, Proboscidea, 

 Hyracoidea, Ungulata, Carnivora, and Primates. 



ORDER I. MARSUPIALIA. 



This order receives its name from the fact that in the 

 female a curious pouch or marsupium is developed on 

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

 placed by the mother immediately after birth, and where 

 they remain until able to take care of themselves. This 

 pouch is supported by a pair of bones which extend for- 

 ward from the pelvis the marsupial bones (fig. 160)- 

 and these, as well as a peculiar inbending of the angle of 



