HIRUNDINID^. 269 



all others the bill weaker, more depressed, the commissure nearly straight 

 to near the tip. 

 The middle toe is lengthened ; the tarsus equal to the toe without the claw, 

 its joint with tihia having overhanging feathers attached, which extend 

 on the inner face of the tarsus a short distance, in Hirundo, Tachycineta, 

 Pterochelidon, Progne. Tarsus similarly feathered, but proportionally 

 longer — being equal to middle toe and half the claw, in Neochelidon, 

 Atticora, Pygochelidon, and Stelgidopteryx. It is of the same proportion, 

 but entirely bare of feathers in Callichelidon and Notiochelidon. 



In Cotyle alone are there short feathers attached to the posterior face of tarsus 

 near the lower end. Here also alone theNUteral claws are very long, 

 reaching considerably beyond the base of the middle claw. 



In Progne and Fhaeoprogne the basal joint of middle toe is adherent but little 

 more than half way externally, about half way internally ; almost the 

 same on both sides. In almost all the rest it is adherent externally 

 nearly to the end, and about half way internally, except in Tachycineta 

 thalassina, where the adhesion is complete on both sides, except at the 

 end of the inner ; in Neochelidon and Notiochelidon, where the basal and 

 half the middle joint : and in Atticora, where the basal and the whole 

 middle joint are adherent externally. 



In Stelgidopteryx the edge of the wing (outer edge of outer primary) is pro- 

 vided with a series of stiff recurved hooks ; in all other American genera 

 these are entirely wanting, though said to exist in the African genus 

 Psalidoprocne, Cab. 



The following synopsis may aid in determining the genera and 

 subgenera of American Hirundinidae, although the succession is not 

 strictly natural : — 



Nostrils broadly oval, or circular ; opening upwards and for- 

 ward, and exposed ; without overhanging membrane. 

 Edge of wing smooth. Tarsus short, stout ; equal to 

 middle toe without claw ; feathered on the inner 

 side above. Nostrils almost or entirely without 

 membrane. 



Bill stout ; culmen and commissure much 

 curved. Frontal feathers without bristles. 

 Tail deeply forked. Color lustrous black ; 

 belly and orisaum sometimes white . . Progne, 

 Similar to last, only culmen straight to near tip ; 

 tarsus with feathers along inner edge for 

 basal half or two-thirds. Fork of tail shal- 

 low. Color mouse brown above ; white be- 

 neath ....... Phaioprogne, 



Bill rather weaker ; commissure and culmen 

 nearly straight to near tip. Frontal feathers 

 bristly. Tail nearly even. Throat, rump 



