FAMILY PITOCIDjE; SEALS. 



231 





assistance in the propulsion of the body. The limbs are con- 

 verted into oars or paddles. The anterior pair have the arm 

 and fore-arm so short, that little more than the paw advances 

 from the body ; in this the bones of the fingers are separate, but 

 they are inclosed in a skin common to all of them, which extends 

 to their tips, so that they are externally marked only by the 

 claws which terminate them. The hinder limbs are directed 

 backwards, so as almost to seem like a continuation of the body ; 

 the thigh and leg are very short, and the foot is formed on the 

 same plan as the fore-paw, the toes being in contact, however, 

 and the web folded, when it is not in use as a paddle, but being 

 spread out into a broad surface when the animal is swimming 

 through the water. Between these paddles is the short and 

 compressed tail. On land, or on masses of ice, the movements 

 of the Seal are awkward, its under-side resting on the ground, 

 and its body being forced onward by the action of the fore-limbs 

 only, whilst the hinder ones are dragged after it. But it swims 

 with great rapidity and ease ; and, by a peculiar arrangement 

 of its blood-vessels, analogous to that which exists in the Whale- 

 tribe, (ANIM. PHYSIOL., 265), it can remain under water for 

 a considerable time. The head is of a rounded form, and is 

 furnished with long stiff whiskers ; the nostrils are provided 

 with a valve, which can be closed at will, so as to keep out 



the water ; a similar 

 valve exists in the 

 orifices of the ears ; 

 and the clothing of 

 the body consists of 

 stiff glossy hairs, very 

 closely set against 

 the skin. The form 

 of the teeth varies 

 considerably in the 

 different genera of 

 this family ; but in 

 all they are adapted rather to hold the slippery prey on which 

 these animals feed, than to cut or to crush what offers much 



Fio. 117. TBKTH or BTRRKINCK. 



