34-4 University of California Publications in Zoology [Vol. 11 



which are brought to play upon these feathers during flight. 

 The long, narrow rami of the inner vane, set at a wide angle, 

 with the shaft, and provided with long slender barbules, are 

 eminently fitted to produce the broad, flexible inner vane 

 required of them, while the short, wide, inflexible rami of the 

 outer vane, set at a narrow angle with the shaft, and possessing 

 short, stout distal barbules with long, strong booklets, and 

 proximal barbules with barbicels, are equallj' well fitted to 

 produce the firm resistant vane which is demanded of them. 



WING COVERTS 

 Greater Upper Coverts 

 Adliering closely to the root of each primary and each sec- 

 ondary, is an upper and a lower greater covert. The quills of 

 the upper coverts arise dorsally to the quills of the remiges, and 

 slightly on the outer side, while the under coverts arise squarely 

 beneath the quills of their respective remiges. The greater 

 upper coverts of the primaries are characterized by the sigmoid 

 curve of the shafts. The covert calamus lies parallel to that of 

 the primary, but at the superior umbilicus the covert shaft 

 swings outward, so that the feather comes to lie between its own 

 primary and the one distal to it. This is also characteristic of 

 the coverts of the secondaries, but on account of their very short 

 calami, the sigmoid character of the curve is not so apparent. 

 The greater upper coverts are further characterized by the 

 great depth of the shaft as compared with its width. At its 

 deepest point, the shaft of the fifth covert is about two milli- 

 meters in depth, while the width is hardly more than one milli- 

 meter. The minute structure does not differ in any way from 

 that of the remiges, the inner vane having normal proximal 

 barbules, and the outer with the barbicelled type on the distal 

 halves of the barbs. There are about thirty-five distal barbules 

 and twenty-four proximal barbules per millimeter. Going from 

 the first to the last of the series there is a gradual reduction of 

 the shaft in size and strength, a pronounced shortening of the 

 calamus, and an increase in the flexibility of the vanes, con- 

 sequent upon a weakening of the rami. 



