BENNETTS ARTICLE OX TUE BEAVER. 319 



increase from their base in the same manner as the incisors; but 

 he has since candidly confessed the error into which he had been 

 led by the inspection of a cranium in which they were not yet 

 fully developed, and he now admits that in the adult animal they 

 arc furnished with true roots, and are consequently incapable of 

 receiving any addition to their growth when once completely 

 formed. Their flattened crowns suinciently indicate that the 

 food which they are intended to masticate is entirely vegetable. 



In the regularity of their line of profile from the back of the 

 head to the extremity of the nose, the lateral position of their 

 diminutive eyes, the depth, obliquity, and obtuseness of their 

 muscle, the vertical fissure of their upper lip, the softness and 

 closeness of their fur, and the greater length and muscularity of 

 their posterior limbs, the beavers may be regarded as almost 

 typical of the order to which they belong. They exhibit, how- 

 ever, in their external form several striking modifications peculiar 

 to themselves. Of these, the most remarkable consists in their 

 tail, which differs in structure from that of every other quadruped. 

 This organ, which is nearly half as long as the body, is broadly 

 dilated, oval, flattened both above and below, covered at its 

 thickened base alone with hair similar to that which invests the 

 rest of the animal, but overlaid throughout the greater part of 

 its extent with a peculiar incrustation which assumes the form of 

 regular scales closely resembling those of fishes. The feet all 

 terminate in five toes, those of the anterior extremities smaller 

 and shorter than those of the posterior, and divided almost to the 

 base, while the latter are united to their very tips by the inter- 

 vention of a strong duplicature of the skin, which allows of their 

 separation to a considerable extent, and forms a broad and pal- 

 mated expansion, similar in form and serving for the same useful 

 purpose with the webbed feet of the swimming birds. The nails 

 are thick and strong; and that of the second toe of the hinder 

 feet is remarkable for being formed of two portions, an upper one 

 corresponding with those of the remaining toes, and an under, 

 placed obliquely, and having a sharp cutting-edge directed down- 

 ward. 



The gait of the beavers is waddling and ungraceful, owing 

 partly to the shortness and inequality of their limbs, and partly 

 to the outward direction which is given to their heels to enable 

 their feet more efficiently to fulfill the office of paddles in swim- 



