Ptyonoprogne Reichenbach. Syst. Av., pl. lxxxvii, fig. 6 (1850).
Type (by subsequent designation, Sharpe, Cat. B. M.), Cotile rupestris.
The genus Ptyonoprogne is very close to the Sand-Mart ins of the genus Riparia but its various species differ greatly in habits and in having white spots on all but the central and outermost tail-feathers.
It has been suggested that Reichenbach's figures of this genus cannot be determined as being those of any one particular genus. They, however, seem to me to show well the characteristics of this group of Swallows and there is no reason why the name should be discarded. Gray, by giving Cotile riparia as the type of Reichenbach's new genus, added to the confusion, no true Cotile or Riparia showing the white spots on the tail as clearly depicted in the plate.
Key to Species.
A. Chin and throat streaked or spotted.
a. Wing over 50 mm.; under tail-coverts much darker than abdomen…………P. rupestris, p. 236.
b. Wing under 50 mm. under tail-coverts and abdomen concolorous…………P. concolor, p. 237.
B. Chin and upper throat unmarked…………P. o. obsoleta, p. 238.