347 



GENUS CASTOR.— Linn. 



DENTAL FORMULA. 



Incisive ^ ; Canine ^^ : Molar -^ = 20. 



Incisors very strong. In the upper jaw their anterior surface is flat 

 and their posterior surface angular. The molars differ slightly from each 

 other in size, and have one internal and three external grooves. In the 

 lower jaw the incisors present the same appearance as those of the 

 upper ; but are smaller. In the molars there are three grooves on the 

 inner side, with one on the external. 



Eyes small ; ears short and round ; five toes on each foot. On the fore- 

 feet the toes are short and close ; on the hind-feet long and palmated. 

 Tail, large, flat, and scaly. Mammae, four, pectoral : a pouch near the 

 root of the tail, in which an unctuous matter is secreted. 



There is but one well established species known to belong to this 

 genus. 



The generic name is derived from the Latin word Castor, a beaver. 



CASTOR FIBER— Linn. 



(VAR. AMERICANUS.) 



AUESICAN BeaVEB. 

 PLATE XLVI. Two-thirds natural size. 



C. Arct. menace major, supra badius, infra dilutior ; cauda plana, 

 ovata, squamosa. 



characters. 



Larger than the ground-hog, {Arctomys monax ;) of a reddish-broivn colour, 

 with a short downy grayish fur beneath ; tail, flat, scaly, and oval. 



