Rivularia plana Harvey in W. Hooker, 1833: 394 (type locality: Miltown Malbay, County Clare, Ireland).
Isactis plana (Harvey) Thuret, 1875: 382.—Frémy, 1941: 20, 28.
INDIAN OCEAN DISTRIBUTION: Djibouti.
Note: Drouet (1973: 238), after examining the holotype of this species (in TCD), referred it to Petrocelis, a genus of Rhodophyceae.