294 University of California Publications in Zoologij FVoi.. 13 



Vanes tapering in both directions from about one-third of distance 

 from calamus to tip of feather. At widest point feather plate 

 about 3 era. wide, total length seldom over 10 cm., thus giving 

 feather a much wider form than in case of Casuariiformes. Barbs 

 14 per centimeter on each side basal ly, 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 

 (pi. 14, figs. 5a, 5&). 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 

 greatly 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 th^' 

 Casuariiformes. 



