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 of 16, 32, 64 cells, subcircular or oval shaped, without perforations; basal parts of the marginal cells obtrapezoid or subpentagon; outer sides of the marginal cell with two small truncate processes having low-triangular base; cell wall granulated (Photomicrographs of the Freshwater Algae, vol. 3, 1985).

31 μm 63 μm 94 μm; x 640

Images of collecting locality: Kenchomae park (a park in front of Prefectural Office), Toyama city, Toyama Pref., Japan, November 18, 2007, by Y. Tsukii