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: Colonies of 4 cells, arranging linearly; cell body spindle-shaped or elongated ellipsoidal, 10-22 μm long, 3-8.5 μm wide; longitudinal ridges on both sides, 2-3 short dented projections (1-1.5 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