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LIFE, IN ITS HIGHEPw FORMS. 



the top with single fangs, called False Molars; and three 



behind all with compound fangs, and broad, somewhat 

 hollow surfaces, called True Molars or grinders. In those 

 races which feed exclusively on flesh, the molar teeth par- 

 take of a cutting character, while in those that subsist on 

 grain and herbage, the molar or grinding structure pre- 

 vails throughout the whole. Sometimes the incisors are 

 curiously developed : in the Squirrel, Rat, and similar 

 animals (Rodentia), they project forwards in a curve, 

 meeting at an angle, and are continually growing; in the 

 Elephant, they stand out in the form of huge curved 

 tusks ; and in the Narwhal, one is commonly undeveloped, 

 while the other grows into a long spirally-twisted straight 

 tusk, like a horn, in front of its head. The Whale has no 

 teeth, but a series of horny plates, parallel to each other, 

 depends from the upper jaw, and constitutes the valuable 

 substance called whalebone. In the Ant-eaters, and some 

 others of the Edentata, there are no teeth at all, while 

 the Armadillo has ninety-six, and some of the Dolphins 

 have a hundred and fifty. 



Considerable variation, suggesting diversity in function 

 and habit, is also found in the forms assumed by the ex- 

 tremities. The Carnivorous tribes, the Rodents, and some 

 others, are furnished with paws, divided into toes, which 

 are terminated by claws: and thus their feet are not only 

 supports in walking, but are endowed with a grasping, tear- 

 ing, or scraping power. On the other hand, the feet of the 

 Thick-skinned and Ruminant tribes are encased in solid 

 hoofs of horn, which may be single, as in the Horse; 

 double, as in the Sheep ; three, as in the Rhinoceros ; four, 

 as in the Hog; or five, as in the Elephant. A hoofed 



