298 University of California Publications in Zoology Vou. 138 
c) Relationships 
The Sphenisciformes must undoubtedly be considered the lowest 
of living aquatie birds, although some of their apparently primitive 
characters may be due to degeneration. The uniform distribution 
of feathers, the absence of specialized remiges and of under wing 
coverts with a reversed position, and the simple structure of both 
their pennaceous and their downy barbules, all point to their 
low systematic position. The broad, flattened form of the shaft, 
and general seale-like appearance of the feathers on the other hand 
are specialized characters. The most logical interpretation is to 
look upon them as derivatives of the extinct, aquatic, toothed birds, 
highly modified by specialization and degeneration for aquatic life. 
d) Summary 
The penguins have the following characters: (1) uniform dis- 
tribution of both plumules and contour feathers; 
(2) So far no filoplumes discovered ; 
(3) No specialized remiges, and no reversed under wing coverts; 
(4) Aftershaft present, its shaft reduced, and the barbs spread- 
ing out tuftlike ; 
(5) Main shaft very broad and flat, usually with no ventral 
groove ; 
(6) Distal barbules very small with a weak base and a series 
of hooked barbicels on pennulum, these barbicels not differentiated 
into ventral teeth, hooklets, and cilia; 
(7) Proximal barbules small but longer than distals, no dis- 
tinct bend or distinction between base and pennulum except the 
presence of simple forward-curving ventral and sometimes also 
dorsal barbicels ; 
(8) Down barbules relatively very short, with a poorly dif- 
ferentiated base, and a filamentous pennulum furnished with well- 
developed prongs, especially toward the tip, where they are always 
larger. 
2. Order COLYMBIFORMES 
Plate 16 
The loons and grebes, which comprise the present order, though 
differing from each other in some details of structure, are very 
similar as regards their epiphyology. Unlike any of the preceding 
birds, they have well-developed apteria, and possess typical fune- 
