Genus: Unicellular; variable in shape; a constriction at the center of the cell body; mostly longer than wide; flattened; each semicell hemispherical, spherical, ellipsoidal, rectangular, pyramidal or kidney-shaped; no apical indentation (Illustrations of The Japanese Fresh-water Algae, 1977). Species [ var. subspeciosum ]: Variety: Cell body 41-50 μm long, 29-36 μm wide; isthmus 11-16 μm wide. [ var. validius ]: Cell body 68-84 μm long, 47-53-(56) μm wide; isthmus 17.5-22 μm wide (Illustrations of the Japanese Fresh-Water Algae, 1977).

31 μm 63 μm 94 μm; x 640