TRICHECHID^E 597 



Phocidce; but when on land the hind feet are turned forwards and 

 used in progression, though less completely than in the Otari></n. 

 The upper canines are developed into immense tusks, which descend 

 a long distance below the lower jaw. All the other teeth (Fig. 

 273), including the lower canines, are much alike, small, simple, 

 and one-rooted, the molars with flat crowns. The skull is without 

 postorbital process, but has an alisphenoid canal. 



Tricheclms. 1 Dentition of young : i f- , c ^, p and m -f-. Many 

 of these teeth are, however, lost early or remain through life in a 

 rudimentary state concealed by the gums. The teeth which are 

 usually developed functionally are i ^, c ^, p f , m % ; total 1 8. 

 Vertebrae : C 7, D 14, L 6, S 4, C 12. Head round. Eyes rather 

 small. Muzzle short and broad, with on each side a group of long, 



Fio. 273. Diagram of the dentition of the Walrus (Trichechus rosmarus). The denticles 

 placed apart from the others are milk-teeth, and disappear soon after birth. The small teeth 

 in connection with the jaws frequently persist throughout life. 



very stiff, bristly whiskers. The remainder of the hair-covering 

 very short and adpressed. Tail very rudimentary. Fore feet with 

 subequal toes, carrying five minute flattened nails. Hind feet with 

 subequal toes, the fifth slightly the largest, having cutaneous lobes 

 projecting beyond the ends as in Otaria ; first and fifth with minute 

 flattened nails ; second, third, and fourth with large, elongated, 

 subcompressed pointed nails. 



TricJiechus is the almost universally accepted generic name by 

 which the Walrus or Morse 2 is known to zoologists, but some con- 

 fusion has been introduced into literature by the revival of the 

 nearly obsolete terms Rosmams by some authors and Odobcenus by 

 others. T. rosmarux is the name of the species met with in the 

 Arctic seas ; that of the North Pacific, if distinct, is T. obesus. The 

 preceding and following descriptions will apply equally to both. 



1 Linn. Stjst. Nat. 12th ed. vol. i. p. 49 (1766). 



- The former word is a modification of the Scandinavian vallross or hvalros 

 (' whale-horse "), the latter an adaptation of the Russian name for the animal. 



