270 REVIEW OF AMERICAN BIRDS. 
and crissum, and usually forehead, rufous ; 
belly white A . . . ° : 
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 Neochelidon 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 
Basal and half the next joint of middle toe ad- 
herent externally to outer toe. 
Tarsus entirely bare : - : d 
Tarsus with feathers on inner face at 
upper end 5 ° . : 4 
Basal joint only of middle toe adherent ex- 
tervally, and free at extreme end. 
Tibial joint covered with feathers whieh 
extend a short distance along inner 
face of tarsus . . . . S 
Edge of wing armed with stiff recurved hooks. Tarsus 
as in preceding (tarsus and toes much as in Pygo- 
chelidon). Bill larger and more depressed. Tail 
emarginate only. Crissum white ° . - 
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 from 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 . . 
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 . . . 
Tarsus with a tuft of feathers at lower end. 
[PART I. 
Petrochelidon. 
Atticora. 
Notiochelidon. 
Neochelidon. 
Pygochelidon. 
Stelgidopteryz. 
Hirundo. 
- Tachycineta, 
