286 University of California Publications in Zoology (Vou. 18 
about 8 per centimeter on each side throughout most of the 
feather, increasing to about 12 or 14 at the base. Rami not lamel- 
late as in most carinate birds, but more closely resembling the rami 
of down; no prominent dorsal or ventral ridges. Inner and outer 
vanes undifferentiated. 
Barbules (pl. 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 difference 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 differmg 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 back, rump, belly, ete., not differing in any 
considerable degree from remiges. Barbs set closer, about 12 to 18 
per centimeter throughout length of feather, usually under 5 em. 
long, basal and distal ones usually shorter resulting in doubly 
tapering form of feathers. Barbules of approximately same form 
as in remiges (pl. 13, fig. 2b, 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 neek, 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 
