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. maximum]: Cell body (92)-114 μm long, (84)-108 μm wide; isthmus 24-(36) μm [var. minor]: Cell body 63.5-(64.5) μm long, 48.5-(56) μm wide; isthmus 10-(28) μm (Illustrations of The Japanese Fresh-water Algae, 1977).

50 μm 100 μm 150 μm; x 400 : 31 μm 63 μm 94 μm; x 640