VERTEBRATA. 295 



chiferus, in which, the male has the canines developed 

 into long tusks, while the female has only very small 

 canines : this is the case also with several other kinds 

 of deer. The Camel and the Dromedary have canines, 

 and use them for aggressive purposes, and the tusks 

 of the Boar are shown in fig. 115. The tusks of 

 the Walrus are the canines, developed so as to enable 

 the animal to tear up seaweed from the rocks, and 

 to climb on land; they are necessary to the animal's 

 mode of life, and are only incidentally used for fight- 

 ing, as may be judged from their development in the 

 female as well as the male. The caniniform tooth is 

 not always the same tooth of the series ; the one 

 which is usually the first premolar is caniniform in 

 the lower jaw of Oreodon, an extinct herbivor. Nor is 

 a tush always a canine : the tusks of the elephant are 

 incisors. 



Insectivorous Dentition. — The molars of insect- 

 eating animals are distinguished from those of the 



Fig. 118. — Insectivorous dentifcionj skull of Mole, Talpa europoea. Dental 

 formula, ?J-^ I *. 



Carnivora by being prismatic in form ; their cusps 

 bear some resemblance in shape to those of Carnivora, 

 but are still more sharp and pointed. The rest of the 

 teeth are often difficult to class in the usual divisions ; 



