AMERICAN HIRUNDINID^ 367 



Nostrils broadly oval, or circular, opening upwards and forwards, and with- 

 out overhanging membrane. 

 Edge of wing smooth. Tarsus short, stout, equal to middle toe without 

 claw, feathered on inner side above. 

 Bill stout; culmen and commissure much curved; frontal feathers 

 ■without bristles ; tail deeply forked ; color lustrous blue-black, 



sometimes with belly and crissum white Progne. 



Like the last ; culmen straight to near tip ; fork of tail shallow ; color 



mouse-brown above, white beneath Phmoprogne. 



Bill weaker ; culmen and commissure above straight to near tip. 

 Frontal feathers bristly ; tail nearly even ; throat, rump, and 



crissum rufous ; belly white Petroehelidon. 



Edge of wing smooth ; tarsus longer than in the last, equalling middle 



toe and half its claw ; nostrils bordered posteriorly with membrane, 



but not overhung internally ; bill very small ; tail forked. 



Basal and whole of next joint of middle toe adherent to outer toe ; tail 



very deeply forked; tarsus feathered above on inner side ..Atlicora. 



Basal and half the next joint of middle toe adherent to outer toe. 



Tarsus entirely bare Aotiochelidon. 



Tarsus feathered above internally ...^ Neochelidon. 



Basal joint only of middle toe to outer toe Pygochelidon. 



Edge of wing armed with stiff, recurved hooks Slelgidopteryx. 



Nostrils lateral; bordered behind and inside, or overhung, by membrane, 

 the outer edge of which is straight, parallel with or diverging from 

 axis of bill. 

 Tarsus about equal to middle toe without claw; tibio-tarsal joint feath- 

 ered, the feathers extending on tarsus along inner side. 

 Tarsus bare below ; lateral claws reaching only to base of middle claw. 

 Tail longer than wings, very deeply forked, with linear lateral feath- 

 ers Hirundo. 



Tail shorter than wings, lightly forked Tachycinela. 



Tarsus with a tuft of feathers at lower end; lateral claws reaching 

 beyond base of middle claw ; tail lightly forked ; color dull brown 



above, white below Cotyle. 



Tarsus equal to middle toe and half its claw, entirely bare. Tail deeply 

 forked, about equal to the wing ; color green above, white 

 beneath Callichelidon. 



Of the groups thus established, Phwoprogne is ranked by 

 Baird as a subgenus of Progne; Noiiochelido7i, Neoclielidon^ 

 and Pygochelidon are considered as subgenera of Atticora, 

 while Tachycineta and CalUchelidon are placed under Hirundo 

 proper. 



In handling the North American sections in 1872, I only 

 differed from Baird in restricting Hirundo to the species with 

 deeply forked tail not shorter than the wings, which required 

 the raising of Tachycineta to generic rank. This left each 

 North American species in a genus by itself, excepting the 



