Chlidonias Rafinesque, Kentucky Gazette, xxxvi, No. 8 (Feb. 1822).
Type by mon., Sterna melanopses, surinamensis Gmelin.
In this genus the bill is short and slightly compressed; legs and feet small, the webs between the toes deeply emarginate so that the feet appear to be only half webbed; claws long and curved. Wings long, exceeding tail when closed; tail short and very slightly forked; all the species are dark grey or black below during the breeding-season.
Key to Species.
A Culmen under 33 mm. ; crown and nape only black in breeding plumage…………C. leucopareia, p. 111.
B. Culmen over 33 mm,; crown, nape and under-pays black in breeding plumage…………C. leucoptera, p. 114.