266 University of California Publications in Zoology  \Vou. 18 
ordinarily developed as a very thin, translucent film, which bends 
distally and overlaps the following ramus, giving a smooth, glazed 
appearance to the under surface of the feather which is conspicuous 
at the most casual glance. It is thus developed in all of the Anseres, 
(pl. 33, fig. 28a), and in a number of gallinaceous birds, though in 
the latter it is by no means constant, being present, for instance, in 
Bonasa, but absent in Lophortyx. The ventral ridge of the outer 
vanes of some groups of birds, e. g., Anseres, Faleconidae, and some 
Ciconiae, is further modified by being furnished with irregular villi 
(fig. C, and pl. 21, fig. 28b) on the ventral edge. The rami of the 
inner vane always have the ventral edge entire or nearly so. 
As shown by Mascha (1904), rami are furnished with a lateral 
‘‘ledge’’ which is grooved for the reception of the bases of the bar- 
bules (fig. C). These are much more highly developed and efficient 
in some birds than in others, often making it very difficult to scrape 
off the barbules without tearing off with them a part of the barb to 
which they remain attached. 
c) Barbules—The interlocking barbules of a typical remex are 
of four distinct types, the distal and proximal barbules of the inner 
vane, and the distal and proximal barbules of the outer vane. 
It is unnecessary here to enter into a discussion of the typical 
structure of distal and proximal barbules, or of their manner of 
interlocking. An excellent description of this is given by Pyeraft 
(1893), and a few additional facts of interest are added by Mascha 
(1904). There are, however, a number of minor details of structure 
of both distal and proximal barbules which are almost uniformly 
different in all birds in the inner and outer vane, although apparently 
this facet has escaped the notice of all previous observers. As a rule 
the bases of the distal barbules of the outer vane are longer and 
relatively narrower than those of distal barbules of inner vanes, but 
this is not always true, the chief difference lying in the pennula. 
On the inner vane the pennulum of distal barbules as a rule is longer 
than it is in the outer vane, with fewer hooklets, but a larger num- 
ber of cells with cilia (compare pl. 16, fig. 8a, with fig. 8c and see 
text-figure D). The most conspicuous difference lies in the dorsal 
cilia on the proximal portion of the pennulum. Almost without excep- 
tion, distal barbules of the inner vanes of remiges are characterized 
by the specialized development of the first two (pl. 20, fig. 20a), 
and often to a less extent of the third, dorsal cilia (pl. 20, fig. 23a). 
These specialized cilia are developed as stout, conspicuous, lobate, or 
