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. abundans): Colonies of 4 cells arranging lineary; cell body ovoid or ellipsoidal in shape, 9-20 μm long, 3-5 μm wide; outer cells with long spines at both ends (6-8 μm long) and short spines at outer side (3-5 μm long); inner cells sometimes have a short spine at both ends (Illustrations of The Japanese Fresh-water Algae, 1977).

31 μm 63 μm 94 μm; x 640

Images of collecting locality: O-ike, Shiroyama Park, Okegawa city, Saitama Pref., Japan, January 29, 2006 by Y. Tsukii