296 University of California Publications in Zoology [Vol. 13 



II. CARINATAE 



All of the birds included in this group differ from those already 

 considered in the following important details: (1) tlie 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 (i. 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-like, 

 with relatively short, stout, appressed barbs, and weak, reduced 

 barbules. 



a) Aptenodytes pennanti 

 (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 cm. long in feather about 4 cm. 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 



