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. subnudum): Cell body (42)-51 μm long, (33.6)-41 μm wide, isthmus 11-(14.5) μm wide, apex slightly depressed; (Illustrations of The Japanese Fresh-water Algae, 1977).