74 



Clark, Pterylosis of Swifts and Hummingbirds. 



fAuk 

 LJan. 



Chaetura. 



(Plate II, Figs. 1-3.) 



The general pterylosis is better shown by the figures given than 

 by any amount of description. The humeral tracts are somewhat 

 narrower than in some genera and less clearly connected with the 

 femoral. The dorsal bands are unusually narrow, especially pos- 

 teriorly. The legs are feathered to the tarsal joint. The skin 

 on the hand is very dark, but not on the forearm. There are 10 

 rectrices, the first longest, the fifth shortest. Of the 10 primaries, 

 the first is longest. There are 8 or 9 secondaries, but the first 6 

 are much longer than the others, and the ninth, when present is 

 very small indeed. The wing is quincubital. The alula consists 

 of 2 feathers. 



Specimens e.va m ined. 



Hemiprocne. 



The general pterylosis is essentially the same as in C/taiura. 

 The ventral cervical apterium is very well defined, and is separated 

 from the great ventral apterium by numerous feathers in the region 

 of the furculum. The femoral tracts are very broad and extend 

 backward to the upper tail-coverts, but their anterior prolonga- 

 tion on the sides is not specially noticeable. The legs are feath- 

 ered to the tarsal joint. The skin of the hand is very dark, but 

 that of the forearm is lighter. There are 10 rectrices, of which the 

 outer ones are longest and the middle pair shortest. Of the 10 

 primaries, the tenth is the longest and the others are successively 

 shorter to the first. There are 10 secondaries and the wing is 

 aquincubital. The alula consists of 3 feathers and a distinct claw. 



