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 surrounded by mucilage; cell body oblong cylindrical with rounded ends, 6.4-17.5 μm long, 1.7-6.6 μm wide; cells arranged in a linear series contacting with about 80% of lateral walls, outer cells slightly convex, with short spines on cell pole in two lateral rows, inner cells on one side with a longitudinal row of short spines; cell wall smooth (Photomicrographs of the Freshwater Algae, vol. 19, 1997).