Subgenus: Entomum (Apical area deeply indented or notched) Section: Incisa (Cell surface smooth; apical area without spiny projections) Species [var. ansatum ]: Cell body medium in size, elongate pyramid-shaped, side margins cocaved, 87-95 μm long, 39-42 μm wide, L/W=2, isthmus 11-14 μm wide; cell wall dotted, with 5 bulges conspicous (2 central, 3 basal) (Illustrations of The Japanese Fresh-water Algae, 1977). Species [var. dideltiforme ]: Cell body 81-109 μm long, 42-53 μm wide, constriction 11-15 μm wide; semicells tapered to terminal lobe, anterior lateral lobes slightly developed

31 μm 63 μm 94 μm; x 640