1916] Chandler: Structure of Feathers 285 
the barbules in some species being more or less intermediate be- 
tween a downy and a pennaceous type. 
1. Order STRUTHIONIFORMES 
Pl. 13, Fig. 2 
This group, which includes only the ostriches, of which four 
closely related species have been described, has a great many 
peculiar epiphyological characters, most of which, it seems to me, 
may be considered primitive, rather than secondarily acquired 
degenerate conditions. They may be enumerated as follows: (1) 
in common with other Ratitae, an even distribution of feathers, 
the only apterium being the central one on the breast, where there 
is a callosity developed by the bird’s habit of resting on its breast, 
and the total absence of plumules and filoplumes; (2) the great 
increase in the number of rectrices and remiges, the latter to 36 or 
more, considered by Beebe (1904) to be a secondary specialization, 
though by some considered a primitive character; (3) the projec- 
tion of the remiges beyond the bone instead of fitting into grooves 
in it as in all earinate birds; (4) the wide angle of insertion of the 
phalangeal primaries, which in other birds are attached almost 
parallel to the long axis of the phalanges; (5) the absence of all 
but one row of under wing coverts; (6) the total absence of after- 
shafts; (7) the total absence of a typical pennaceous structure in 
the feathers. 
a) Struthio camelus 
(1) Remiges 
The feathers of ostriches, as already stated, are all of one type, 
and not differentiated into contour feathers, plumules, and_filo- 
plumes. The aftershaft is entirely lacking. The rectrices and 
remiges are developed into very large, curling plumes with loose, 
drooping vanes, but in their minute structure differ in no essential 
way from any of the body feathers. 
Shafts relatively stout, usually widely and more or Jess deeply 
grooved’ beneath. In male wing plumes, for instance, the groove 
so deep and prominent as to make the shaft C-shaped in eross- 
section and shell-like almost to tip. Width of the shaft of a 
small wing plume, 6 to 7 mm. at the base, tapering gradually all the 
way to the end; its depth about 4 mm., 3 mm. of which is involved 
in the groove. 
Barbs, which may reach a length of 15 or 20 em., usually set 
