332 University of California Publications in Zoology [Vol.13 



measure than in any group previously studied, about 28 distals and 

 12 or 13 proximals per millimeter. 



Inner vane. — Distal barhules (pi. 22, figs. 34a, 346) 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 booklets, followed by a few 

 long, slender ventral cilia, the distal portion devoid of them. Two 

 basal dorsal cilia developed as in Plotns, 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 346. Proximal barbules (pi. 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 (pi. 22, fig. 34d) differ from those of inner 

 vane mainly in possessing larger number of booklets, in greater 

 development of ventral cilia, and in absence of dorsal ones. Prox- 

 imals, as sliown 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 slightly more separated from 

 one another and assuming more of a toothlike form. Typical 

 ventral cilia not developed. 



h) 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 hav- 

 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 dowai barbules are hardly differentiated from the pennula, 

 being very narrow. 



