Anous Stephens, in Shaw's Gen. Zool., xiii, pi. i, p. 139 (Feb. 1826).
Type by orig. desig., A. niger Stephens = Sterna stolidus Linn.
The genus Anous differs from Sterna in having the third or fourth pair of tail-feathers longest, not the outermost.
The bill is long, slender and considerably curved towards the end of the culmen; the nostrils are situated in a groove and are still further from the base than in Sterna; the tarsus is very short, much shorter than the middle toe without claw; the feet are large with fully-webbed toes; the wing is long with the first primary longest.
Two species are found within Indian limits which, are sometimes divided into two genera, Anous and Micranous, but the differences seem more specific than generic and I retain them both in Anous. The genus is represented throughout the Tropical and Subtropical seas.
Key to Species.
A. Wing over 270 mm.; crown grey; fourth pair of tail-feathers longest……………A. stolidus, p. 145.
B. Wing under 240 mm.; crown white; third pair of tail-feathers longest……………A. minutus, p. 147.