

114 MAMMALIA. GLIIIES. 



posterior longer and palmated; tail broad, thick, flattened hori- 

 zontally, of an oval form, naked, and covered with scales. 



C.Jiher, Lin. The Beaver. Fur consisting of two sorts of hair, 



one coarse and brownish, the other downy,, more or less gray. 



About two feet long. North America and Europe. Penn. Brit. 



Zool. i. pi. 9. 



The Beaver has been long celebrated for its intelligence and social instinct. It 

 is found on the banks of rivers and lakes in North America, living in troops more or 

 less numerous in a kind of huts, constructed near the margin of the water. They 

 intercept the water, to form ponds attached to their dwellings, by strong arched dikes, 

 of which the convexity is opposed to the current. These dikes are formed of stones, 

 mud, and branches of trees. Their huts, composed of the same materials, are situ- 

 ate on the margin of the ponds, and generally of an oval form, with a rounded top, 

 the diameter of which is proportioned to the number of individuals who are its in- 

 mates. The entrance to this cabin is from the lowest part, descending into the water, 

 through which alone they enter, the principal part of the dwelling being above its 

 level. The beaver uses its teeth to cut the branches of trees necessary for its pur- 

 pose, as well as to transport the different materials of its structure ; and the com- 

 bination of means to this end in a number of individuals has approximated in the 

 minds of some the social instinct of animals to something approaching to reason. 

 But in captivity the beaver shows nothing of the social instinct, and very little in- 

 telligence. The period of gestation in the beaver is four months, and it brings 

 forth two or three young. They are at their full size in two years, and the dura- 

 tion of their life is about fifteen. 



The beaver is subject to considerable variety of colour, and individuals have been 

 noticed from totally black to different shades of yellow or fawn-colour and white. 



A fossil species, the C. trogontherium of Fischer, resembles in its characters the 

 present species, though its dimensions seem to have been much larger. 



Gen. 92. FIBER, Cuv. Geoff. Mm. Gmel. 



Incisors f , canines g-g, molars f-f =16. Molars with a flat 

 crown, and scaly angular zigzag plates of enamel ; fore-feet 

 with four toes and the rudiment of a thumb ; posterior with 

 five, edged with stiff and close bristles ; tail long, compressed 

 laterally, naked, except a few scattered hairs, and granular. 



F. Zibethicus, Desm. (Castor Zibethicus, Lin.) The Ondatra or 

 Musk Rat. Fur clear brown, tinged with red above, cinereous be- 

 neath. About the size of a rabbit. Canada Buff- x. pi. 1. 



Gen. 93, AEVICOLA, Desm. Mus 9 Lin. Lemmus, Geoff. 



Incisors f , canines -g, molars f-f = 16. Molars with a flat 

 crown and angular plates of enamel ; ears large ; anterior toes 

 with nails ; tail round, hairy, almost the length of the body. 



A. amphibius, Desm. (Mus amphibius, Lin.) The Water Rat. 

 Fur blackish -gray, slightly mixed with yellowish, lighter beneath ; 

 tail black. A little larger than the common rat. Old and New 

 Continents. B. Buff. vii. pi. 43. 



Var. A. All black Var. B. With a large white spot on the shoulders. Var. C. 



Black, feet covered with white hairs. 



A. Argentoratensis, Desm. Fur of a brownish black, mixed with 

 gray ; tail brown, almost naked. Six inches long. Found near 

 Strasbourg. Buff. Sup. vii. pi. 70. 





