FLESH-EATING MAMMALS. 



The true or earless seals constitute the last family of the fin-footed Car- 

 nivora, and are those best adapted for a thoroughly aquatic life, the hind- 

 flippers being permanently directed backwards alongside of the tail, and ex- 

 ternal ears totally wanting. A further difference from the 



eared-seals is to be found in the circumstance that the under True Seals. 



surface of the feet is hairy ; and in no case is there any under- Family Phocufa. 

 fur, the ordinary fur being short and closely pressed to the 

 skin. All the species have five pairs of cheek teeth in each jaw, but the 

 number of incisors is variable. Oil land, most of the true seals advance by a 

 jumping movement, produced by the muscles of the body, assisted only by 

 the front-flippers. 



The common grey seal (Halichoerus grypus), of the coasts of the whole 

 North Atlantic, is the type of the sub-family Phwidce, characterised by having 

 three pairs of upper, and two of lower incisor teeth, well- developed claws on 

 all the toes, and the hind-toes of 

 nearly equal length, with the webs 

 not reaching beyond their extremi- 

 ties. In the grey seal the cheek- 

 teeth, except the last one or two 

 in the upper, and the last in the 

 lower jaw, are single-rooted, and 

 consist generally of a single com- 

 pressed cusp, although additional 

 cusps may be present in the two 

 hinder pairs in the lower jaw. 

 The typical seals (Phoca), all of 

 which are confined to the Northern 

 Hemisphere, differ from the last in 

 that all the cheek teeth are of smaller size, and, with the exception of the first 

 pair in each jaw, are inserted by double roots, and have accessory cusps to 

 their crowns. As examples of this genus may be cited the bearded-seal 

 (P. barbata\ Greenland seal (P. grcenlandica), common seal (P. vitulina), the 

 Caspian seal (P. caspica) from the Caspian and Sea of Aral, and P. sibirica 

 of Lake Baikal. Like other members of their tribe, these seals resort to the 

 coast to bring forth their young, which may be either one or two in number ; 

 and not the least remarkable fact in their life-history is the circumstance 

 that the offspring have to be taught by their parents to enter the water. 

 They usually congregate in large herds, and are especially fond of lying bask- 

 ing in the sun like so many pigs. Seals are regularly hunted for the sake of 

 their hides and blubber, the latter yielding a valuable oil. 



A second sub-family of the Phocidce. is typified by the monk-seal of the 

 Mediterranean and adjacent portions of the Atlantic, which, with the nearly 

 extinct West Indian seal, constitutes the genus Monachus. In this sub-family 

 there are but two pairs of incisor teeth in each jaw, the cheek teeth, with 

 the exception of the first pair, are inserted by two roots, and the first and 

 fifth toes of the hind-flippers much exceed the three middle ones in length, 

 and have their claws rudimental or wanting. The monk-seal is characterised 

 by the possession of 32 teeth, and by the crowns of the cheek teeth 

 being hollowed on the inner side where there is a strongly marked basal 

 ledge arid their front and back accessory cusps very small. The first cheek 

 tooth in both jaws, as well as the last in the upper, are considerably smaller 

 than the rest ; and all the claws are rudimental. The four other generic 



Fig. 53. COMMON SEAL (Phoca vitulina). 



