Genus: Colonies of 4 (or 2, 8, 16) cells attached side by side, arranged linearly or zigzag; cell body elliptical or spindle or crescent in shape; terminal cells with spiny projections in many species; cell wall usually smooth, but in some species granulated or dented or ridged (Illustrations of The Japanese Fresh-water Algae, 1977). Species [ var. acuminatus ]: Colonies of 4 or 8 cells; cells arranging linearly (4 cells) or zigzag (8 cells); cell body elongated spindle-shaped, outer cells curved outward, 12-30 μm long, 2.5-6 μm wide; cell wall smooth (Illustrations of The Japanese Fresh-water Algae, 1977).

31 μm 63 μm 94 μm; x 640

Images of collecting locality: A drainage ditch around Sakura castle ruin park (and National Museum of Japanese History), Sakura city, Chiba Pref., Japan, March 16, 2008 by Y. Tsukii