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. Subgenus [ Eucosmarium ]: Cell body dorso-ventrally compressed, with strong constriction at the center, transverse section elliptical or diamond-shaped. Section [ Ornatae ]: Semicells circular, ellipsoid, reniform; cell surface granulated or spiny (Illustrations of The Japanese Fresh-water Algae, 1977). Species:

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