SPECIES OF MAMMALIA. 



Order IV.— RODENTIA. 



Two large incisors in each jaw, separated from the cheek- 

 teeth by a void space, and which wear by use, and grow 

 again on the inner side. No canine teeth ; cheek-teeth in 

 some genera with flat or ridged crowns, in others, with 

 blunt tubercles. Lower jaw articulated by a longitudinal 

 condyle ; orbits not separated from the temporal fossae ; zy- 

 gomatic arches small ; toes variable in number; nails un- 

 guiculated ; stomach simple ; intestines long ; caecum large. 



Eats in general vegetable matter, but the species with 

 tuberculated teeth are nearly omnivorous. 



Habits various, generally timid. 



Inhabits the Continents, and larger islands, but not those 

 of the South Sea. 



Section I. — With Clavicles. 



Genus I. 



Castor. — Incisive teeth, I ; canines, gj] » cheek-teeth, 

 ji=20. Incisive teeth very strong, with the anterior surface 

 Hat, and the posterior, angular ; the cheek-teeth with a 

 sort of fold or ridge of enamel on the internal edge, and 

 ;hree similar folds on the external edge of the upper teeth, 

 ivhich apparent folds are inversed in the lower teeth ; eyes 

 small ; ears short and round ; five toes on all the feet, the 

 interior short and close, the posterior longer and palmated ; 

 ail large, flat, naked, and scaly ; a pouch, into which an 

 mctuous matter is secreted near the genitals of the male. 



531. 1. Castor Fiber {the Bcavev.) Rather larger than 

 he Badger, uniformly reddish brown, with a shorter downy 

 ;ray fur. 



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