Species [ var. obsoletum]: Cell body medium in size, broad elliptical (wider than length), 34-(39-50) μm long, 42-(48-53)-54 μm wide, isthmus 15.5-(21-25) μm wide; semicells semielliptical or depressed semicircular, cell wall at basal corner thickened like a papillae; cell wall punctated and dotted. [ var. sitvense ]: Cell body relatively large in size, 57-(69-78) μm long, 67-(69-78) μm wide, isthmus 30-(39-42) μm wide (Illustrations of The Japanese Fresh-water Algae, 1977).

31 μm 63 μm 94 μm; x 640

Images of collecting locality: Block 3, Kashibaru marsh, Karatsu city, Saga Pref., Japan, September 9, 2008 by Y. Tsukii