RODENTIA. 80 



substances, their incisors are very powerful, and grow as rapidly from the root 

 as they are worn away at the point. With these teeth they cut trees of every 

 description. 



They have large glandular pouches, which produce a highly odorous oily 

 substance, employed in medicine under the name of Castor oil. 



C. fiber, Buff. (The Beaver.) Larger than the badger, and of all quadru- 

 peds the most industrious in constructing a dwelling, to effect which these 

 animals act in concert. They are found in the most solitary parts of North 

 America. 



Beavers choose water of such A depth as is not likely to be frozen to the 

 bottom, and, as far as possible, running streams, in order that the wood which 

 they cut above, may be carried downwards by the current to the spot where it 

 is to be used. They keep the water at an equal height, by dams composed of 

 branches of trees, mixed with clay and stones, the strength of which is annually 

 increased, and which finally, by the progress of vegetation, becomes converted 

 into a hedge. Kach hut serves for two or three families, and consists of two 

 stories ; the upper is dry for the residence of the animals, and the lower under 

 water for their stores of bark, &c. The latter alone is open, and the entrance 

 is under water, having no communication with the land. The huts are a kind 

 of rude wicker-work, being made of interwoven branches and twigs of trees 

 plastered with mud. There are always several burrows along the bank, 

 in which they seek for shelter when their huts are attacked. They only reside 

 in these habitations during the winter: in the summer they separate, and live 

 a solitary life. The Beaver may be easily tamed, and accustomed to feed on 

 animal matter. It is of a uniform reddish brown colour, and the fur, s is 

 well known, is in great demand for hatters. It is sometimes found flaxen- 

 coloured, at others black, or even white. 



MYOPOTAMUS, Comaner. 



The Couias resemble the Beaver in size, in their four nearly similarly com- 

 posed molars, in their powerful yellow-tinted incisors, and in their five-toed 

 feet, the hinder ones of which are palmated; but their tail is round and 

 elongated. They are aquatic animals also. One only is known, the 



M. coipus.' (The Couia.) Which lives in burrows along the banks of rivers 

 throughout a great part of South America. 



HYSTRIX, Linnceus. 



The Porcupines are known at the first glance by the stiff and sharp spines, or 

 quills (as they are called), with which they are armed, like the hedge-hogs 

 among the Carnaria. Their grinders are four throughout, with flat crowns, 

 variously modified by plates of enamel, between which are depressed intervals. 

 Their tongue is bristled with spiny scales, and their clavicles are too small to 

 rest upon the sternum and scapula, being merely suspended by ligaments. 



