﻿22 ON THE CLASSIFICATION OP BIRDS. 



gins of the upper mandible fold over those of the lower ; 

 while in others, as the finches, the two edges meet. The 



n g c a 



line thus formed by the meeting of the mandibles is 

 termed the commissure (/) : it is either straight, as in the 

 woodpeckers ; festooned, as in the sparrow-hawk ; undu- 

 lated, as in some of the tanagers (fig. q 1.) ; arched, as in 

 the bullfinch ; or angulated at its base, as in the starlings. 

 In many birds, the upper mandible is continued far 

 back on the front or forehead, and there dilated, so as 

 to resemble a sort of casque or helmet : this is seen in 

 the shrike-crows (Barita, Vanga, &c), in the cassicans, 

 and slightly in the finches. In rapacious birds and 

 parrots, there is a belt of soft naked skin at the base 

 of the upper mandible, in which the nostrils are placed ; 



