334 University of California Puhlications in Zoology [Vol. 13 



and dorsal cilia, except basal two, rudimentary. The latter not 

 so stout or so close together as in the Cathartae but more so than 

 in the Falconidae, Proximal barhulcs (pi. 22, fig. 35cZ) relatively 

 small and of typical falconid type. 



Outer vane. — Distal harhules differ from those of inner vane in 

 the greater length of the booklets and in the shorter cells of the 

 pennulum, the latter resulting in the close approximation of the 

 ventral cilia, so that they appear brushlike. Proximal barbules 

 have well-developed, hooked ventral cilia, as in Accipitres. 



Distal to the incision of the feather, where vanes are narrowed, 

 distal barbules of inner vane do not possess dorsal barbicels, and 

 proximal barbules of outer vane do not have hooklike ventral cilia. 

 The latter are developed but lie closely appressed to the barbule. 



(2) Back Feathers 



Gray hack feathers of Gypogeranus with distal barbules with 

 relatively large pennula, furnished with small, rather weak hook- 

 lets and long, slender, closely set ventral cilia. Pigment concen- 

 trated in spots, resulting, as in gulls, in bluish tinge in gray color 

 (pi. 22, figs. 35a, 35&). 



(3) Down 



The down barbules do not materially differ from those of other 

 Falconiformes, being moderately elongate, reaching a length of 

 2 mm. or more, the base poorly developed, and pennula very slender 

 with slightly enlarged nodes, which, especially at tip, are furnished 

 with short, inconspicuous prongs. 



h) Summary and Relationships 



The Gypogerani are much nearer to the Accipitres than to the 

 Cathartae as far as feather structure is concerned. They agree 

 more closely with the Cathartae in the character of the dorsal cilia 

 of the distal barbules of the inner vane, but in all other details of 

 structure they are almost identical with the Accipitres. 



III. Suborder Accipitres 



The birds of this suborder form a compact, well-defined group, 

 including the hawks, eagles, ospreys, and Old World vultures. The 

 owls used to be associated with this group until further investigation 

 showed that they were in reality widely separated, with many points 

 in common as the result of parallel evolution and similar adapta- 

 tion. The morphology of the feathers agrees with the osteology, 

 myology, and other characters in showing that the Striges really 

 have nothing in common with the Accipitres as regards near rela- 

 tionship. As in other Falconiformes, the plumules of the Accipitres 

 are uniformly distributed, and in a few forms powder-down is 

 present. The aftershaft is present, and usually well developed. 



