296 Unwersity of California Publications in Zoology  lVour.138 
Il. CARINATAE 
All of the birds included in this group differ from those already 
considered in the following important details: (1) the presence of 
apteria in all but the Spenisciformes and Palamedeidae; (2) the 
presence, or undoubtedly secondary loss, of plumules and _ filo- 
plumes; and (3) presence in the adult of both downy and pen- 
naceous structures, while the nestling feathers are always downy. 
1. Order SPHENISCIFORMES 
Plate 15 
The epiphyology of this group differs widely in a number of points 
from that of all other living birds. With the sole exception of the 
Palamedeidae, they are the only carinate birds with an absolutely 
uniform distribution of feathers, the contour feathers and plumules 
both being evenly distributed over the entire body. No specialized 
remiges are developed and it seems probable that the first row of 
feathers on the posterior margin of the wing is not homologous to the 
remiges of other birds, but represents the under wing coverts, the 
third row of feathers representing the true remiges; this interpreta- 
tion is based on the fact that in these birds there are no under wing 
coverts with a reversed position (1. e., umbilicus exposed), as there 
are in all other birds (Wray, 1887a). The rectrices are represented 
by a row of feathers which have the shaft very stiff and spine-lke, 
with relatively short, stout, appressed barbs, and weak, reduced 
barbules. 
a) Aptenodytes pennantt 
(1) Body Feathers 
Details of feather structure very distinct from that of birds of 
any other group. Calamus cylindrical and transparent, constricted 
at superior umbilicus, where it gives off the shaft and an aftershaft. 
The shaft of latter sub-triangular, about 0.1 mm. wide at junction 
with calamus, widening out to about 0.4 mm. in the 2 mm. of its length, 
then giving off a large number (50 or more) of very delicate, downy 
barbs about 1.5 em. long in feather about 4 em. long, Down of after- 
shaft like that of main feather plate, except barbules shorter. 
Shaft remarkably broad and flat, in feather under consideration 
about 2.5 mm. wide a short distance distal to superior umbilicus, con- 
siderably under 1 mm. in depth, tapering gradually to tip; very flat, 
only slightly convex above and below, a slight median ridge on each 
surface. Rami attached to narrow edge of shaft, thus not nearer 
