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 

 PI. 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 carinate 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 less deeply 

 grooved beneath. In male wing plumes, for instance, the groove 

 so deep and prominent as to make the shaft C-shaped in cross- 

 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. 



Barls, which may reach a length of 15 or 20 cm., usually set 



