A new species of Hibiscus (Malvaceae, Malvoideae) from Guyana.

Hibiscusmarioniae Dorr, sp. nov. is described and illustrated. It evidently is restricted to central Guyana, northeast of the Kanuku Mountains near the Rewa River, a tributary of the Rupununi River. The new species is most similar morphologically to H.amazonicus Fryxell, which was described from Amazonas, Brazil.