Species [ var. abbreviatum ]: Cell body (11-15)-22 μm long, (11-14.5)-22 μm wide, L/W=1.0, isthmus (4.2-5.6)-7 μm wide; semicells broad hexagon in shape. [ f. minor ]: 8-8.4 μ;m long, 8.5-9 μm wide. [ var. planctonicum ]: (14)-19-29 μm long, (14)-22-30 μm wide; each corner rounded, apical margin convex. [ f. pygmaea ]: Cell body smaller, upper side of lateral margins longer than lower side and concave, 11-14 μm long, 12-14 μm wide, isthmus 4.2-6 μm wide. [ var. gremanicum ]: Apical and lateral margins slightly concave, 12.6 μm long, 11.2 μm wide, isthmus 3.4 μm wide (Illustrations of The Japanese Fresh-water Algae, 1977).

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