1916] Chandler: Structure of Feathers 263 
merely vestigial or rudimentary structures. No suggestion of a pos- 
sible use has yet been made. 
III. Contour FEATHERS 
Under contour feathers, in their various forms and modifications, 
may be included practically all of the diverse kinds of plumage ordi- 
narily displayed on the body of a bird. In this category come all 
remiges, rectrices, coverts, and exposed body-feathers, except in a 
few instances where filoplumes or plumules are exposed, as in cormor- 
ants and on the neck of Pelecanus respectively ; also ear-coverts, eye- 
lashes, rictal and other bristles, and all sorts of ornamental crests 
and plumes, and other modified feather structures, such as the brush 
of a turkey, the ‘‘wires’’ of some birds of paradise, the lyre of 
Menura, ete. Their variety of form is almost limitless, yet they are 
all modifications of the same fundamental structure. A discussion 
of the various important types of feathers in a typical bird of flight 
has been made for Circus hudsonius by me, (1914) and it is only 
necessary here to generalize on the conditions found there, and show 
along what lines phylogenetic modifications of this type have taken 
place in the whole series of birds. 
1. Remiges 
a) Shaft—The most highly specialized feathers, those in which 
the structure reaches its height of perfection, are the remiges, espe- 
cially the primaries, of strong-flying birds. These feathers, in all 
flying birds, have a well-developed quill, differentiated into a hollow 
calamus and a stiff shaft which is more or less rectangular in cross- 
section, and usually has a groove running along the ventral side, 
generally quite pronounced at the superior umbilicus and becoming 
obliterated towards the tip of the feather. The condition of the 
groove varies to a considerable extent in different groups of birds, in 
some being broad and shallow, in some narrow and deep, and with all 
gradations between in others. In the remiges of ostriches the ventral 
groove of the shaft reaches its maximum size, the shaft in this case 
being in the form of a half-cylinder, convex above and concave below, 
while in some of the higher birds, e. g., Coccyzus, there is no groove 
whatever. These facts at first glance would indicate that a large, 
wide-open ventral groove is a primitive character, that the absence 
