332 Unwersity of California Publications in Zoology  'Vour. 18 
measure than in any group previously studied, about 28 distals and 
12 or 13 proximals per millimeter. 
Inner vane—Distal barbules (pl. 22, figs. 34a, 34b) with large 
bases, about 0.4 mm. long by 0.05 mm. wide. Stout base of the distals 
furnished with moderate, lobate ventral teeth; the pennulum stout, 
with about 5 stout, progressively longer hooklets, followed by a few 
long, slender ventral cilia, the distal portion devoid of them. Two 
basal dorsal cilia developed as in Plotus, forming stout, blunt, 
laterally projecting, spinelike processes; all the other dorsal barbi- 
cels rudimentary. Distal to these characteristic dorsal cilia there is a 
bend in dorsal contour of barbule as shown in the figures. When 
detached, barbules usually lie in the position shown in plate 22, 
figure 34b. Proximal barbules (pl. 22, fig. 34c) with relatively 
small bases, a series of moderate ventral teeth, and pennulum 
which is broad proximally, but rapidly tapering to fine thread. 
Pennulum somewhat shorter than base. 
Outer vane.—Distals (pl. 22, fig. 34d) differ from those of inner 
vane mainly in possessing larger number of hooklets, in greater 
development of ventral cilia, and in absence of dorsal ones. Prow- 
imals, as Shown by plate 22, figure 34e, very similar to those of 
inner vane, but slightly larger, and ventral teeth a little more 
prominent, at extreme tip becoming shghtly more separated from 
one another and assuming more of a toothliike form. Typical 
ventral cilia not developed. 
b) Other Types 
Cathartes aura has practically the same types of barbules, though 
smaller and the barbicels not so stout. On the broad basal portion 
of the primaries, the proximal barbules at the tip of the barbs have 
the ventral teeth transformed into toothlike cilia, but they are not 
proliferated and do not become slender or hooked. 
The back feathers of Cathartes aura have barbules resembling 
those of the outer vane of the remiges, the distals differing in havy- 
ing a very stout heavy pennulum, with fewer and more slender teeth, 
and with stout appressed ventral cilia. The breast feathers have 
the barbules very much simplified and reduced. No flexules are 
ever developed. 
c) Down 
The down barbules of Cathartae are very long and _ slender, 
with the nodes only marked by slight enlargements, showing best 
on the proximal vanule, the internodes being very long. The bases 
of the down barbules are hardly differentiated from the pennula, 
being very narrow. 
