﻿62 



ON THE CLASSIFICATION OF BIRDS. 



thus to be found only in the two typical orders of 

 birds, the Raptores and the Incessores ; in all others it 

 is entirely wanting. There is yet a third mode by 

 which nature supplies the deficiency of real teeth to 



the bill of birds; and 

 that is, by dividing the 

 edges into a number of 

 saw-like notches, of 

 greater or less size as 

 the peculiar habits of 

 the birds require. The 

 first developement of 

 this structure is seen 

 in the double-toothed 

 falcons, as in the genus 

 Harpagus (fig. 28. a); 

 the next is in the ty- 

 pical trogons (h), and 

 in the sub-genus An- 

 dropadus* (c) : a fur- 

 ther advance is seen in the toucans and hornbills, where 

 the serratures, although coarse and wide apart, extend 

 the whole length of the bill : but the highest develop- 

 ment is exhibited in the Chizcerhis variegata (d), 

 where the teeth are small, sharp, regular, and of equal size. 

 In the Musaphaga violacea (fig. 29.) , on the other hand, 



they are somewhat un- 

 equal, and nearly obsolete 

 towards the base of the 

 cutting margins. We 

 cannot, unfortunately, il- 

 lustrate any one of these 

 structures by detailing 

 corresponding traits in 

 the economy of the birds. 

 There is one, however — 

 the plant-cutter of Chili — whose bill is described as much 



* North. Zool. vol. ii. p. 485. The Importan of Lc Vaillant (Ois. d'Af. 

 pi. 106. f. 2.), but recently described as a new bird by Jardin and Selby under 

 the name of Trichophorus brachypodioidcs. 111. of Om. pi. 128. 



