334 University of California Publications in Zoology Vor. 18 
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 Faleonidae. Proximal barbules (pl. 22, fig. 35d) relatively 
small and of typical faleonid type. 
Outer vane.—Distal barbules differ from those of inner vane in 
the greater length of the hooklets 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 back 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 
(pl. 22, figs. 35a, 35D). 
(3) Down 
The down barbules do not materially differ from those of other 
Faleoniformes, 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. 
b) 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. 
