THE TEETH OF CARNIVORA. 



391 



name of ' saw-toothed seal ' has been given to their pos- 

 sessors. 



In the Hooded seals (Cystophora) the incisors are re- 

 duced to one in the lower jaw and two in the upper ; the 



FIG. 172 ('). 



canines are of great size, but the molars are small and 

 simple in form, so as to approximate to the teeth of true 

 Cetacea. 



The walrus (Trichechus rosmarus), an aberrant Arctic 

 form, is possessed of enormous upper canines, which pass 

 down outside the lower lip, and are of such dimensions as 

 to materially modify the form of cranium by the size of 

 their sockets ; they grow from persistent pulps, and are 

 composed of dentine with a thin investment of cement. 



The great tusks are employed to tear up marine plants 

 and to turn over obstacles, the walrus feeding upon Crus- 

 tacea, and also iipon seaweed, &c. ; they are also used to 

 assist the animal in clambering over ice : as they are of 

 almost equal size in the female, they cannot be regarded as 

 weapons of sexual offence, but they are undoubtedly used 

 in the combats of the males. 



") Permanent and milk teeth of Elephant Seal (Cystophora proboscidea). 



