THE TEETH OF MAMMALS 153 



fish, and is simplified, and less highly specialized 

 than in other Carnivora. The incisors are ranch 

 reduced and often absent. The canine and even 

 the molar series are simple and conical, being 

 adapted to hold their struggling, slippery prey. 

 The molar series are of typical triconodont form. 

 In the Walrus the upper canines are elongated to 

 form projecting tusks which reach far below the 

 lower jaw. These are employed to assist in loco- 

 motion, to turn over rocks in seeking for food, and 

 as formidable weapons of defense. In the Phoci- 

 clas the milk teeth are shed during fetal life in 

 some species. 



