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: Cell body spindle in shape or long ellipsoid, slightly curved, tapered at both ends, 15-20 μm long, 4-8 μm wide, cell body covered with short thin spines, outer cells with 2-3 long spines at both ends, inner cells with 2-3 long spines at only one end, cells attached side by side, slightly zigzag (Photomicrographs of the Freshwater Algae, vol. 15, 1995).
Similar species -->> S. denticulatus;
cell 19 x 6.5 μm
spines 2-2.5 μm
cell 14 x 4.5 μm
spines 1.5-2 μm