BIEDS OP NORTH AND MIDDLE AMERICA. • 715 



Rhaphidura Gates, Birds Burmah, ii, 1883, 6. (Type, Acanthylis leucopygiaiis 



Blyth.) 

 Acanthura<' Guildinc;, Zool. Journ., iii, 1827, 407. (Type, Hinaido acuta 



"Stephens" i. e. Gmelin.) 



Small Cluyturiiio Swifts (wing about lOO-loO juiii.) resembling 

 CypseloiAes but with the hallux relatively much smaller (less than 

 hah as long as inner toe) and with shafts of the rectrices more rigid, 

 usually conspicuously extruded terminally. 



Nostrils elliptical, nearly parallel, for the most part anterior to the 

 latero-frontal antia;; distance from tip of longest secondar}' to that 

 of longest primary about two-thirds the total length of wing; tenth 

 and ninth primaries longest, usually nearly or quite equal in length, 

 but sometimes one or the other a little shorter, the tenth (outer- 

 most) more or less narrowed (sometimes subacuminate) terminally; 

 tail (to base of spines) less than two-ninths to more than one-third 

 as long as wing, truncate or slightly rounded, very firm, the shafts 

 very rigid and, usually, conspicuously extruded terminally, forming 

 spine-like tips; tarsus equal to or longer than middle toe with claw, 

 entirely naked, nonscutellate; outer toe slightly shorter, the inner 

 toe shghtly to decidedly shorter, than middle toe; hallux very 

 small and weak, less than half as long as inner toe.'' 



Coloration. — Plain sooty or blackish, sometimes with a gray or 

 whitish rump-patch or band, one species w^ith the rump, tail-coverts, 

 and tail light gray in contrast with rest of plumage. 



Nidifi cation. — Nest in form of a half saucer or shallow cup, com- 

 posed of dried twigs glued together by salivary excretion and at- 

 tached by same substance to the inner wall of a hollow tree, chimney, 

 or similar place. 



KEY TO THE SPECIES AND SUBSPECIES OF CH.ETURA. 



a. Under parts of body and under tail-coverts gray or sooty, concolor with or paler 

 than tail. 

 b. Rump brownish gray or grayish brown, concolor with tail and not conspicu- 

 ously lighter than back; tail relatively shorter (only two-sevenths as long 

 as wing). 

 c. Under parts and rump darker brownish gray or grayish brown. 

 d. Larger (wing 122-133 mm.); pileum and back not blackish. (Eastern 

 North America, south to eastern Mexico in winter.) 



Chsetura pelagica (]). 717). 



a "AKavda, thorn, spine; oupa, tail. (Richmond.) 



b According to Lucas (Auk, xiii, 1896, 82) Chxtura (C. pelagica at least) is peculiar 

 among the North American genera of Swifts in lacking the deltoid muscle. This 

 muscle is present not only in other North American genera but also in Tachornis, 

 Streptoprocne, CoUocalia, and Macropteryx (double in the last, single in the rest). It 

 is not known, however, whether it is present or absent in Panyptila, Claudia, Mi- 

 cropus, or Cypseloides, or other species of Chsetura than C. pelagica. (See Auk, xvi, 

 1899, 77, as to deltoid muscle in Streptoprocne.) 



