270 REVIEW OF AMERICAN BIRDS. [PART I. 



and crissum, and usually forehead, rufous ; 



belly white Petrochelidon. 



Edge of wing smooth. Tarsus longer than in last ; 

 equal to middle toe and half the claw. Nostrils 

 bordered along posterior half by membrane, but 

 not overhung internally. Bill very small. Tail 

 forked. Crissum dusky, except Neochel idon fucata. 

 Basal and whole of next joint of middle toe ad- 

 herent externally to outer toe. Tail very 

 deeply forked. 



Tarsus feathered at upper end internally Atticora. 

 Basal and half the next joint of middle toe ad- 

 herent externally to outer toe. 



Tarsus entirely bare .... Notiochelidon, 



Tarsus with feathers on inner face at 



upper end ..... Neochelidon. 



Basal joint only of middle toe adherent ex- 

 ternally, and free at extreme end. 



Tibial joint covered with feathers whieh 

 extend a short distance along inner 

 face of tarsus ..... Pygochelidon. 

 Edge of wing armed with stiff recurved hooks. Tarsus 

 as in preceding (tarsus and toes much as in Pi/go- 

 chelidon). Bill larger and more depressed. Tail 

 emarginate only. Crissum white . . . SteJyidoptenjx. 



Nostrils lateral ; bordered behind and inside, or overhung by 

 membrane, the outer edge of which is straight, and di- 

 rected either parallel with axis of bill or diverging frorfi it. 

 Tarsus short ; about equal to middle toe without claw. 

 Tibial joint feathered; feathers extending along 

 inside of upper end of tarsus. 



Tarsus bare at lower end. Lateral claws reach- 

 ing only to base of middle. 

 Tail very deeply forked, much longer than 

 closed wings ; lateral feathers linear, 

 and very narrow at end, twice the 

 length of central. Upper parts and 

 pectoral collar steel blue ; front and 

 throat, sometimes under parts, rufous. 

 Tail feathers with large spots . . Hirundo. 

 Tail with shallow fork, not exceeding half 

 an inch, shorter than closed wings. 

 Feathers broad. Color blue or green 

 above, with or without white rump ; 

 white beneath ..... Tachycineta. 

 Tarsus with a tuft of feathers at lower end. 



