192 



FLESH-EATERS OF THE SEA 



muscles, by means of which the body is contracted and 

 thrown forward by a succession of ungainly jerks. 



Naturalists have arranged the 

 Seals in various technical divi- 

 sions. Traders adopt a simpler 

 classification, dividing the diverse 

 varieties into Hair Seals, Fur Seals, 

 and the Walrus, the first-named 

 being of service for their hides 

 and oil, the second supplying skins 

 from which are made the ' sealskin' 

 garments that are so highly prized. 

 To economise space and the reader's 

 patience only a few of the more 

 notable typical examples will be 

 offered for consideration. 



Scientifically the Seals may be 

 roughly divided into the Phocidae, 

 or true Seals ; the Otariidae, or 

 Eared Seals ; and the Trichechidae, 

 or Walrus, of which only one 

 species is in existence. These 

 groups may be easily distinguished. 

 The Phocidae have no external ears ; 

 the Otariidae have small pointed 

 ears ; and the Walrus has two 

 enormous tusks projecting from the 

 upper jaw. 



One peculiarity in all the Seals is 

 worthy of notice. The nostrils are 

 surrounded by a muscle, called a 

 sphincter, i.e., a constrictor, by 

 which the nostrils are kept closed 

 until required, when they can be 

 opened while the creature breathes, 

 closing again automatically, without 

 any exertion on the part of the 

 animal. The object of this structure is to prevent water 

 passing into the lungs while the Seal is below the surface. 

 When we come to the Whales, we shall find that the same 



