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 oblong with both ends rounded, 15-35 μm long, 4.5-5.8 (-9) μm wide; cells arranged in a linear series contacting nearly with their entire sides; outer cells with a long curved spine at each ends, sometimes inner cells with a long spine at one pole; cell wall smooth or covered with linear microgranules (Photomicrographs of the Freshwater Algae, vol. 17, 1996).