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: Cells attached side by side along 3/4 of their side (arranging in 1 or 2 rows), inner spaces absent (cf. S. arcuatus); cell body ellipsoidal or ovoid without spiny or dented projections, 7-20 μm long, 4-10 μm in diam. (Illustrations of The Japanese Fresh-water Algae, 1977).

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