225 



RODENTIA 



OR 



GNAWING QUADRUPEDS. 



THE animals, generally of small size, and almost 

 always phytophagous, which collectively have re- 

 ceived the names of Glires and Rodentia, are 

 readily distinguishable from all others by their pecu- 

 liar dentition. They have two large incisors in 

 each jaw, between which and the grinders is an 

 empty space, there being no canine teeth. The' 

 front teeth are of a prismatic form, chisel-shaped 

 at the end, continually grow from the root or base, 

 in proportion as they are worn; and should one 

 happen to be displaced, the corresponding tooth ot 

 the other jaw, finding no obstacle to its growth, 

 attains a great elongation. The lower jaw being 

 articulated by a longitudinal condyle, has a hori- 

 zontal motion backwards and forwards, and the flat 

 crowns of the grinders are marked with transverse 



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