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).

31 μm 63 μm 94 μm; x 640

Images of collecting locality: No.5, Omine-numa (pond/marsh), Omine, Minakami town (formerly Tsukiyono town), Gunma Pref., Japan, October 21, 2007 by Y. Tsukii