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, 8 cells, arranging linearly; cell body elongated spindle-shaped, with distinct ridges on both sides, 12-28 μm long, 5-8 μm wide; outer cells with long spiny projections on both ends; inner cells with two dented projections on both ends (Illustrations of The Japanese Fresh-water Algae, 1977).

Similar species -->> S. opoliensis (no ridges); S. armatus (small & ridges incomplete);

31 μm 63 μm 94 μm; x 640