298 University of California Publications in Zoology I Vol. 13 



c) Relationships 



The Sphenisciforines must undoubtedly be considered the lowest 

 of living aquatic 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 scale-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, booklets, 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 func- 



