ORDERS OF MAMMALIA. 



345 



or heel, on the inside of its cutting edge. In various Carnivores a 

 number, or all, of the prsemolars and molars may be " tuberculate," 

 their crowns being adapted for bruising rather than cutting. As a 

 general rule, the shorter the jaw, and the fewer the prsemolai'S and 

 molars, the more carnivorous is the animal. The jaws are so articu- 

 lated as to admit of vertical but not of horizontal movements ; and 

 the sharp-edged back-teeth are thus enabled to act like the blades 

 of a pair of scissors. 



Besides the strictly flesh-eating dentition of the Carnivora, the 

 order is distinguished by always having the feet provided with 

 strong curved claws ; and the collar-bones {clavicles) are either quite 

 rudimentary, or are altogether absent. The Carnivora are divided 

 into the following three sections, founded upon the nature of the 

 limbs : — 



1. Pinnigrada (fig. 250, B), in which both the fore and hind legs 

 are short, and the feet form broad, webbed, swimming -paddles. 

 The hind-feet are placed very far back, nearly in a line with the 

 axis of the body, and they form with the hinder end of the body a 

 powerful caudal fin. In this section are the Seals and Walruses. 



Fig, 250.— Feet of Carnivora (after Owen). A, Plantigrada, Foot of Bear ; 

 B, Pinnigrada, Hind-feet of Seal ; C, Bigitigrada, Foot of Lion. 



2. Plantigrada (fig. 250, A), comprising the Bears, in which the 

 whole, or nearly the whole, of the foot is applied to the ground, so 

 that the animal walks upon the soles of the feet. 



3. Digitigrada (fig. 250, C), comprising the Cats, Lions, Tigers, 

 Dogs, &e., in which the heel is raised from the ground, and the 

 animal walks upon tiptoe. 



