654 MAMMALIA. 



and more unwieldy forms, assistant locomotive organs have been 

 given, derived from unlocked for sources. Thus, in the Walrus 

 (Trichecus rosmarus), which apparently obtains nourishment 

 from the fuci of the shore, as well as by destroying living prey, 

 even the canine teeth of the upper jaw are converted into instru- 

 ments of progression, and serve as crutches to drag the animal 

 along. In these creatures the upper jaw is extremely dilated and 

 massive, and the canine teeth implanted in it not unfrequently 

 project downwards to a distance of from one to two feet from the 

 mouth. The strength of the tusks so formed is proportionate to 

 the bulk of this gigantic Seal, and by their aid the Walrus is en- 

 abled to climb on to the rock in order to repose after its labours in 

 the ocean. 



(734.) The Terrestrial Carnivora, that live upon flesh, are na- 

 turally divisible into two great sections. Of these, the most cruel 

 and blood-thirsty, called from this circumstance " Digitigrada," 

 walk only upon their toes, and bound along with an elasticity and 

 swiftness that are abundantly provided for in the construction of 

 every part of their osseous system. In this section are classed the 

 extensive tribes of Weasels (Jig. 307), and of Civets, the Hyenas, 



and the race of Cats, the most formidable and ravenous of 

 quadrupeds. 



In the Feline Carnivora, indeed, to which belong the Lion and 

 the Tiger, so justly celebrated for their strength and ferocity, a 

 peculiar and beautiful provision is visible in the construction of the 

 foot, whereby the claws that arm the last phalanges of the toes are 

 kept constantly sharp, their points never being allowed to become 

 worn by touching the ground ; hence they are in these crea- 

 tures terrific instruments of attack. The mechanism provided for 

 effecting this is as follows : three elastic ligaments, derived from 



