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. pachydermum): Cell body 78-117 μm long, 60-87 μm wide, isthmus 25-34 μm wide (Illustrations of The Japanese Fresh-water Algae, 1977).