Discussion:19. Potamoganos Sandwith, Rec. Trav. Bot. Neerl. 34: 220. 1937.
Type. Potamoganos microcalyx (G.F.W. Mey.) Sandw.
This monotypic genus is related to Roentgenia and Cydista and shares with them a ''Cydista-type" flower and cupular calyx. Unhke these genera Potamoganos has a well developed disc. It lacks glandular fields, has terete branchlets, and trifid tendrils. The corolla is magenta. The single species is known only from lowland Guayana and its fruit has never been discovered.