Genus: Colonies of a fixed number of cells, flat, circular in shape; cell body polygonal in shape, with horn-like projections; cell wall garanulated, wrinkled or notched; chloroplasts plate-like or reticular; asexual reproduction by zoospore; sexual reproduction by isogametes (Illustrations of The Japanese Fresh-water Algae, 1977). Species: Colonies without perforations, 12-74 μm in diam.; all cells with a deep incision, cell wall smooth ; marginal cells with two triangular processes extending outward, triangular (colonies with small number of cells) or trapezoid (large colonies) at base, 5-18 μm in diam., 4-18 μm long; inner cells five to seven angled, 4-16 μm in diam., 4-14 μm long (Photomicrographs of the Freshwater Algae, vol. 5, 1986).

31 μm 63 μm 94 μm; x 640

Images of collecting locality: No.2, Nozomiko (Lake Nozomi), Madarao highland, Iiyama city, Nagano Pref., Japan, April 26, 2007 by Y. Tsukii