26 BULLETIN 50,. UNITED STATES NATIONAL MUSEUM. 



In short, while the number of genera allowed in the following pages 

 may seem excessive, to my mind it expresses far better than does a 

 more limited number the true relationships within the family. 



KEY TO THE GENERA OP HIEUNDINID^E. 



a. Nostrils opening superiorly, broad, roundish, without distinct, if any, inner 



operculum. 



b. Larger (wing not less than 123 mm., usually much more); bill stouter, less 



depressed, the culmen strongly decurved, at least terminally. 



,. Inner side of tarsus with less than upper half feathered; tail equal to or 



longer than distance from bend of wing to tip of longest secondaries, the 



lateral rectrices distinctly narrowed terminally; culmen more strongly 



curved, and bill thicker; upper parts (at least in part) glossy blue-black, the 



under parts also glossy blue-black in adult males of some species. (Sexes 



more or less different in color. ) Progne (p. 28) 



cc. Inner side of tarsus with more than upper half feathered; tail shorter than 

 distance from bend of wing to tip of longest secondaries, the lateral rectrices 

 not distinctly narrowed terminally; culmen straight to near tip, the bill 

 more depressed; upper parts dull brownish gray; under parts white with 

 brownish gray across chest and along sides, the center of breast with 



brownish gray spots. (Sexes alike. ) Phaeoprogne (extralimital)o 



bh. Smaller (wing not more than 118 mm., usually much less) ; bill weaker, much 

 depressed, with culmen straight to near tip. 

 (-. Subbasal phalanx of middle toe entirely free from outer toe. 

 d. Basal phalanx of middle toe not entirely adherent to outer toe. 

 'e. Tarsus decidedly shorter than middle toe with claw (scarcely, if at all, 

 longer than middle toe without claw) ; back streaked with white or 



grayish; rump cinnamon or chestnut Petroohelidon (p. 44) 



ee. Tarsus nearly as long as middle toe with claw, or at least decidedly longer 



than middle toe without claw; back not streaked; rump not cinnamon 



or chestnut. 



/. Tail much more than half as long as wing, forked for nearly one-fourth 



its length, the lateral rectrices distinctly narrowed terminally, with 



tip obtusely pointed; wing- tip decidedly longer than distance from 



bend of wing to end of longest secondaries; above glossy blue-black or 



dark steel blue, beneath white with blue-black imder tail coverts. 



Pygochelidon (p. 68) 

 ff. Tail less than half as long as wing, slightly emarginate, all the rectrices 

 broad and rounded at tip; wing-tip little if any longer than distance 

 from bend of wing to end of longest secondaries; above dull grayish 

 brown with a tawny or rusty bar across nape and on sides of head; 

 beneath white, becoming cinnamomeous on throat. 



Alopochelidon (extralimital)'' 



aPhseoprogne Baird, Review Am. Birds, May, 1865, 272, 283. (Type, Hirundofusca 

 Vieillot. ) (South American; two species, which are remarkably similar in coloration 

 to Riparia riparia. ) 



b Alopochelidon, new genus. (Type, Hirwidofucaia Temminck. ) This genus comes 

 very close to Stelgidopteryx, but differs in less extent of adhesion of toes, and in the 

 entire absence, apparently, of recurved tips to the barbs of outer web of outermost 

 primary, the latter being wanting in the young, and often in adult females, of 

 Stelgidopteryx. The coloration is quite the same, except that Alopochelidon has the 

 head largely tawny or rusty. The genus is monotypic and confined to the South 

 Brazilian region of South America. ('AXooko?, fox-colored; ^eA75(»7', a swallow.) 



