The genus Oxystigma Selys, 1862 (Zygoptera: Megapodagrionidae)

A revision is given of the genus Oxystigma, with the type species Heteragrion petiolatum Selys, 1862 from Santarem on the Amazon River. Two other species of Oxystigma are described from the Guyanas, one of which was misidentified by WILLIAMSON (1919, Occ. Pap. Mus. Zool. Univ. Mich. 68: 1-88), who considered it identical with the type species Santarem, and which is redescribed here under the name of O. williamsoni sp. n., <5 holotype and 9 allotype taken in tandem during oviposition at Zanderij, Pontji Creek, Surinam (Jan. 8, 1947), and are deposited in the Leiden Museum. Of the same species the oviposition is described and figured for the first time. Of the third species, O. cyanofrons Wlls. (type locality British Guiana, now Guyana), additional data are presented with notes on its larval stage.