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 (Illustrations of The Japanese Fresh-water Algae, 1977).