286 University of California Pnhlications in Zoology fVoL. 13 



about 8 per centimeter on each side tliroujz:fiout most of the 

 feather, increasing to about 12 or 14 at the base. liami not lamel- 

 late as in most carinate birds, but more closely resembling the rami 

 of down; no pr-omincnt dorsal or ventral ridges. Inner and outer 

 vanes undifferentiated. 



Barhules (pi. 13, fig. 2a) differing widely in form from those 

 of any other birds, either ratite or carinate, at once recognizable. 

 Not differentiated either into distal and proximal, or outer vane 

 and innner vane types, nor any considerable diff'erence in structure 

 and form, except length, in different parts of feathers, or in feathers 

 of different parts of the body. Barbules not clearly differentiated 

 into base and pennulum, even to the extent of ordinary down 

 barbules, and further differing from the latter in being flat and 

 ribbonlike instead of filamentous, in this particular approaching 

 pennaceous barbules but differing from them in being bilaterally 

 symmetrical. On best developed barbules, no prongs or barbicels 

 whatever, but small rudimentary prongs, as in barbules of body 

 feathers, on weaker ones at base and tip of barbs. Length of bar- 

 bules from 2.5 to 3.5 mm. ; width, about 0.035 mm., this being 

 comparable with that of pennaceous barbules ; on an average about 

 25 to 30 barbules per millimeter on each vanule, thus more widely 

 spaced than usual with ordinary down barbules. 



(2) Other Feathers of Adult 



The feathers of hack, rump, belly, etc., not differing in any 

 considerable degree from remiges. Barbs set closer, about 12 to 18 

 per centimeter throughout length of feather, usually under 5 cm. 

 long, basal and distal ones usually shorter resulting in doubly 

 tapering form of feathers. Barbules of approximately same form 

 as in remiges (pi. 13, fig. 25, 2c), those of the less well-developed 

 feathers with rudimentary prongs at the junction of the cells, called 

 "vestigial barbicels" by Beebe (1904). Length variable, less than in 

 remiges, usually under 2 mm. 



Feathers of head and neck small, with elongated, bare, hairlike 

 shafts. Eyelashes present, in form of stiff, coarse bristles, with a 

 few basal barbs. Specialized ear coverts present, similar in general 

 plan to those of carinate birds, the shaft furnished with a series of 

 stiff and elastic bristle-like barbs, entirely separate from each other, 

 arranged like the tufts of a brush rather than in distinct vanes, and 

 barbules very small, rudimentary, and appressed. In all small 

 feathers of head and neck, including eyelashes and ear coverts, 

 elongated, bristle-like shafts naked, but barbs always with complete 

 series of densely set and very short barbules, only 0.015 to 0.03 mm. 

 long, but of typical ribbon-like form. 



(3) Nestling Feathers 

 The nestling feathers of ostriches have exactly the same type of 

 structure of barbules as teleoptiles, which fact furnishes some 

 evidence that the latter are not degenerated pennaceous barbules 

 but are highly developed downy ones, since down barbules are the 

 only ones ever found in neossoptiles. The barbules of the latter 



