1916] Chandler: Structure of Feathers > 33 
middle portion of the barbs. The pennula are short, not over half 
the length of the bases. In no birds which I have examined is 
there a greater difference between the leneth of the bases of distal 
and proximal barbules on the same barb. To counterbalance this 
great difference in size, in order to produce fairly equivalent 
vanules, the angle of insertion of the distals is unusually wide, 
while that of the proximals is unusually acute, this in turn result- 
ing in an astonishing difference in number of barbules per unit of 
measure. While there are 40 or more distals per millimeter, there 
are only 16 or 17 proximals for the same distance. 
On the outer vane the distal barbules differ from those of the 
inner vane only in the absence of the dorsal cilia, and sometimes in 
the presence of one more hooklet. The proximals (pl. 19, fig. 17c), 
except on a small portion of the tip of the barb, are similar 
to those of the inner vane except that they are short, and rela- 
tively broader. On the distal part of the barb the ventral teeth 
increase to about six in number, become separated, and are trans- 
formed into very long, stout, curved barbicels, resembling the teeth 
of a large-toothed comb. The pennulum is shortened so that it 
does not extend more than one cell beyond the barbicels; the base 
is likewise shortened and reduced. 
The primaries of Pelecanus californicus are similar to those 
described above. The secondaries and coverts, however, have the 
distals transformed to produce the characteristic hoary effect. 
These barbules (pl. 19, fig. 18a) have their bases reduced in size, 
the hooklets shortened, and the pennula elongated, with a double 
series of long, slender cilia. They resemble very closely the distal 
barbules of the hoary feathers of Phalacocorax (pl. 18, fig. 14e), 
but the pennula are not so broad, while the cilia are longer and 
more prominent. 
In the breast feathers of Pelecanus, at the base of the barbs 
the barbules have a structure similar to that found in Sula and other 
Steganopodes, a proximal barbule from this portion being shown 
in plate 19, figure 17e. The outer portion of the barb, however, 
develops typical flexules on both distal and proximal barbules, ex- 
actly as in the Procellariiformes. Plate 19, figure 17d, shows a 
distal barbule from a breast feather of P. erythrorhynchus and 
comparison with plate 17, figure 10e (Diomedea exsulans) will 
show the striking similarity. At the extreme tip both barbules 
assume the form shown in plate 19, figure 19e (Phaéthon), which 
