MAMMALS 



313 



all our beasts of burden. It would be almost impossible for man 

 to exist without this important group of animals. 



The Carnivora (flesh eaters) are very highly specialized in 

 structure for the pursuit of prey, and in fact,, live largely upon 

 the ungulates whose adaptations have been along the line of keen 

 senses and swiftness to escape this very danger. The carnivora 

 have large, interlocking canine teeth, shear cutting molars, a very 

 strong jaw hinge, and 

 enormous muscles attached to 

 ridges on the skull. Their 

 skeleton is light and slender, 

 the jaw short and strong, and 

 the feet usually provided with 

 claws. These claws, in the cat 

 family, can be withdrawn into 

 sheaths, which keeps them 

 sharp and also permits a noise- 

 less approach upon their prey. 



On the other hand, the dog 

 family cannot withdraw the 

 claws, which are therefore blunt and not used for prehension, but 

 for swiftness of chase, which is characteristic of their manner of 

 hunting. Their keenness of sight and smell have been especially 

 adapted for their manner of life. 



The carnivora include two divisions: (1) the aquatic forms (seal, 

 sea lion, walrus) in which the limbs are short and web-footed; 

 (2) the land forms with long limbs and separate toes. These 

 land forms are divided into three groups, according to the manner 

 of walking: 



1. Those walking flat on the foot (bear, raccoon). 



2. Those walking on the toes only (dog, wolf, fox, hyena, cat, 

 tiger, lion, leopard, etc.). 



3. Those walking partly on the toes (martin, mink, weasel, otter, 

 sable, skunk, etc.). 



It will be noticed that, except for the dog and cat, none of the 

 carnivora are domestic animals, and few of them are used as food, 



FIG. 103. After Wiederscheim. 



