294 Unwersity of California Publications in Zoology Vou. 138 
Vanes tapering in both directions from about one-third of distance 
from calamus to tip of feather. At widest point feather plate 
about 3 em. wide, total length seldom over 10 em., thus giving 
feather a much wider form than in case of Casuariiformes. Barbs 
14 per centimeter on each side basally, only 9 or 10 towards tip of 
feather, set at right angles to shaft on lower part of feather, the 
angle gradually becoming more acute toward tip, so that even 
though barbs are actually considerably longer, the vanes taper 
evenly. Barbs on basal part of feather furnished with barbules 
for whole length, but towards tip barbuliferous portion more and 
more restricted to basal portion of barbs, the terminal parts of 
which are elongated into moderately slender, black hairs lying 
close to each other, and with totally different appearance from the 
bare, coarse barbs of cassowaries and emus. Barbules very slender 
and filamentous, of typical downy type. Base short, but well- 
formed, about 0.017 mm. wide. Pennulum 0.008 mm. in diameter, 
varying from perfectly smooth filament in basal barbs to filament 
with distinct nodes and minute prongs in more’ terminal barbs 
(pl. 14, figs. 5a, 5b). In well-developed downy region of vanes, 
barbules from 2 to 3 mm. in length, set 25 to 35 per millimeter, 
but in more terminal portion, where reduced, diminishing greatly 
in length, but concomitantly stouter, with more distinct prongs. 
Little variation in structure in different feathers. Around base 
of bill a few long, hairlike rictal bristles developed, formed by 
ereatly elongated shafts of minute facial bristles. 
b) Relationships 
Apteryx apparently has a peculiar mingling of primitive, special- 
ized, and degenerate characters, but, as hinted under Casuariiformes, 
its feather structure suggests a rather closer affiliation to the Casuarii- 
formes than to any other birds, and it seems best to regard the genus 
as an early offshoot from the stem leading to the latter group. 
The presence of vestigial (rudimentary?) apteria in these birds 
has been considered by many authors as indicative of their descent 
from a type possessing well-formed apteria, but it seems to me that 
there is fully as much ground for looking upon this feature as a 
beginning rather than a vestige. As in the case of other ratite 
birds, the absence of differentiated plumules and filoplumes is much 
more easily thought of as a primitive than as a degenerate char- 
acter. The remiges and rectrices may have been better developed 
in their ancestors, but there seems to be no positive ground for 
believing that they ever possessed lifting power. The absence of 
the aftershaft may be a primitive or a secondarily acquired char- 
acter. Its absence is the chief epiphyological divergence from the 
Casuariiformes. 
