376 University of California Publications in Zoology f^oL. 13 



type for their entire length, and have short internodes (pi. 37, 

 fig. 112). The down barbules of a large number of genera of 

 Trochilidae have been examined, and all of them have been found 

 to possess this type of structure. The barbules on the outer part 

 of the barbs have inconspicuous nodes, of a type similar to that 

 shown in plate 37, figure 110. 



The Trogons have down very much like the Trochilidae in that 

 the nodes are large and conspicuous and present for the entire 

 length of the pennula, but they are not relatively as large, or the 

 internodes as short, and the bases are not furnished with villi. 

 The nodes are shaped more or less like the fruit of a eucalyptus 

 tree and are deeply pigmented. 



The down barbules of the Pici, like the pennaceous barbules, 

 show a close similarity to the Passeriformes except in the family 

 Galbulidae. In the latter, as exemplified by Bucco, Malacoptera 

 and Jacamerops, the down is like that of Coracias and Momotus. 

 In the Ehamphastidae (Rhamphastus, Pteroglossus and Andigena) 

 the barbules (pi. 37, fig. 113) have large nodes shaped like euca- 

 lyptus fruits on the proximal portion, these becoming small and 

 insignificant beyond the basal 6 or 7. The bases of the inner bar- 

 bules have weakly developed villi. The barbets, Capitonidae, have 

 down almost exactly like the Rhamphastidae. In the Picidae the 

 type is similar except that the basal nodes are relatively smaller, 

 and the decrease in size toward the tip of the barbules is more 

 gradual and less conspicuous. The villi on the bases are well- 

 developed on the barbules near the base of the barbs, as much so 

 as in many Passeriformes. 



d) Color Modifications 



The variety of colors found in the Coraciiformes is unexcelled 

 anywhere amongst birds, and the variety of structural modifica- 

 tions correlated with color production is correspondingly great. 



Many of the Coraciiformes are characterized by the prevalence 

 of deep purple and light blue colors in the wings and tail. The 

 deep purple is a brilliant purple refraction color produced by the 

 large dorsal ridges of the rami, combined with a blackish brown 

 pigmentation in the non-refractive barbules. The beautiful light 

 blue of these birds is produced by a superstructure above the 

 refrangent surface of the dorsal ridges of the rami which otherwise 

 produce brilliant purple, the barbules in this case being unpig- 



