Species: Cell body 14-22 μm long, 23-32 μm wide, constriction 22-.30.4 μm wide (Illustrations of The Japanese Fresh-water Algae, 1977). Cell body 14-22 μm long, 23-32 μm wide, outline shape transversely rectangular, slightly constricted in the middle, vertically circular (f. dissiliens), sometimes with a slight papilla in opposite disposition (f. bidentula) or three ones equidistantly (f. tridentula); semicells subtrapeziform, lateral margin convex; cell wall punctated; filaments not twisted (Photomicrographs of the Freshwater Algae, vol. 1, 1984).