1916] Chandler: Structure of Feathers 367 



green of many species is produced by a brilliant green structural 

 color in the ramus, accompanied by a brown pigmentation in the 

 barbules, the depth and tone of the green varying with the shade 

 and amount of brown pigment in the barbules. The bright emerald 

 green of Melopsittacus is produced by green or blue rami, with 

 lemon-yellow barbules, and the yellow olive-green of Tanygnathus 

 lucionensis by green rami and barred barbules which are yellowish 

 proximally (pi. 30, fig. 76a.). The deep purple or blue of some 

 species is produced by a brilliant purple or blue structural color 

 in the rami, and a dark brown pigment color in the barbules. One 

 of the most interesting combinations is in the feathers on the side 

 of the head of Palaeornis cyanocephalus, which are described as 

 rosy, with a bloom like that of a ripe plum. This is produced by 

 a light purplish blue structural color in the rami, and a red pig- 

 ment color in the barbules. 



e) Relationships 



In all respects of feather structure, the Cuculiformes are very 

 closely related to the Coraciiformes, and should probably be con- 

 sidered as nearly allied to the immediate forerunners of this group. 

 The question of their descent is likewise easy, the only lower groups 

 to which they show affinity being the peristeropode Galli and the 

 Columbae ; in general form of pennaceous barbules they are nearer 

 to the former, but in the structure of the down and in some details 

 of the structure of the pennaceous barbules, e. g., the prongs on 

 the booklets, they show affiliation with the latter. The Cuculi, 

 especially the Musophagidae, come nearer the gallinaceous and 

 columbid birds, while the parrots are nearer the Coraciiformes in 

 the structure of their feathers. 



f) Summary 



(1) Plumules evenly distributed in Psittaci, sparse and con- 

 fined to apteria in Cuculi. 



(2) Aftershaft present in Psittaci, rudimentary or absent in 

 Cuculi, 



(3) Distal barbules and proximal barbules about equal in 

 number. 



(4) Distal barbules with -wevj elongate base with sinuous ven- 

 tral contour, ventral teeth very small; pennulum shorter than base, 



