378 University of California Publications in Zoology TVol. 13 



colors which are due entirely to refraction, the pigment being of a 

 totally different color. It is interesting to note that in blue 

 iridescent feathers the underlying pigment is a rich rufous brown, 

 in green a duller fuscous brown, and in all shades of red a very 

 dark olive-green, brighter in the fiery red of Selasphorus rufus 

 than in the lilac or ruby red of other species. This phenomenon 

 is explained by the theory of selective transmission and reflection, 

 colors which are readily reflected being poorly transmitted. 



In various other types of coraciiform birds still other interesting 

 color modifications are to be found, only a few of which may be 

 mentioned here. The coppery green of Jacamerops grandis is pro- 

 duced by barbules very similar in form to those of hummingbirds, 

 the color being reflected from the portion of the barbule not curved 

 over, as in Petasophora. Green in the Capitonidae is produced in 

 an interesting manner, the portion of the ramus ventral to the 

 attachment of the barbules having a deep yellow pigment color, 

 while dorsal to the barbules the rami are curved • over flangelike, 

 contain a rich brown pigment, and produce a blue structural color. 

 The combination of blue and yellow by reflected light gives the 

 effect of green, while by transmitted light it is orange brown. The 

 depth and tone of the color varies with the pigment in the non- 

 refrangent barbules. In the woodpeckers the red crests which are 

 so frequently found owe their color to prolonged, cylindrical rami 

 which are filled with a deep red pigment. The peculiar effect of 

 the white and red streaked breast of Asyndesmus torquatus is due 

 to a deep red pigmentation in the dorsal half of the rami, and a 

 white effect in the ventral half, appearing under the microscope 

 like a miniature snow bank, due to the countless minute air spaces 

 which cause diffusion of light. 



e) Relationships 



The Coraciiformes, as stated at the beginning of the discussion 

 of them, constitute a rather heterogeneous assemblage of birds which 

 lie between the Cuculiformes and the lower orders on the one hand, 

 and the Passeriformes on the other. The Coraciidae and near 

 allies, Striges, Caprimulgi, Bucerotidae and Cypselidae, have types 

 of feathers which are to be regarded as independent offshoots from 

 the main line of evolution. The trogons seem to be more nearly in 

 the line of descent of the passerine birds, the Rhamphastidae and 

 Capitonidae of the suborder Pici connecting them with the latter 



