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. quadricauda ]: Colonies of 2, 4 or 8 cells arranging linearly; cell body elongated ellipsoidal, 11-18 μm long, 3.5-7 μm wide; terminal cells with long spiny projections (10-17 μm long); cell wall smooth. [ var. biornatus ]: Cell body 7-15 μm long, 3-5 μm wide; all cells have spiny projections (5-14 μm long) at both ends (Illustrations of The Japanese Fresh-water Algae, 1977).

50 μm 100 μm 150 μm; x 400 : 31 μm 63 μm 94 μm; x 640