﻿EXTERNAL ANATOMY. MOBILE CRESTS. 3Q 



to these we add the Phibalura cristata* , one of the 

 swallow chatterers ; the Oocyrhynchus cristatus t, among 

 the climbing creepers ; and two species of Tiaris, among 

 the tanagers — we are not aware of any other birds, 

 independent of the American flycatchers, whereon this 

 peculiar sort of crest is developed. 



(47.) The third class of crests differ from the two 

 former in not being mobile ; that is to say, they are of 

 such a structure as always to remain, more or less, fixed 

 and elevated in the same position. They are formed by 

 the feathers on each side of the head being disposed as 

 if they had been raised up, and then compressed to- 

 gether, so as to leave a ridge or keel rising up along the 

 centre of the skull, precisely similar to the elevated 

 ridge of a helmet ; or, to express this structure more 

 technically, these crests are vertically compressed, and 

 carinated. There are, comparatively, so few exam- 

 ples of this structure, that we should not expect to find 

 it much diversified ; and yet it appears under many 

 curious modifications. The first, or incipient indication 



of this form, is seen in 

 those birds which, like 

 the satin grakles (Pti- 

 lonorynchus, fig. 17») * 

 many of the true gra- 

 kles (Lamprotornince), 

 have the small frontal 

 feathers closely pressed 

 round the base of the nostrils and upper mandible, and 

 very slightly raised just above the front : this, however, 

 cannot be called a crest, but is rather the commencement 

 of one. In several of the swallow shrikes {Edolinai), 

 nature advances another step ; for here we see some of 

 the frontal feathers not only more elevated than the 

 others, but even slightly elongated ; next we find them 

 curled backwards, so that the drongup of Le Vaillant %, 



* Zool. Illust. i. pi. 13. 



f Cres ted sharpbill, Zool. Illust. i. pi. 49. 



X Ois. d'Afrique, pi. 170. 



D 4 



