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 sometimes surrounded by mucilage; cell body cylindrical to spool-shaped, with broadly rounded ends and slightly concave sides, 10-21 μm long, 3-8 μm wide; cells arranged in a linear series contacting at the polar regions of the sides making intercellular perforation between the cells; outer cells with slightly convexed outer side and a long, slightly curved spine at each corner; cell wall smooth or punctate (Photomicrographs of the Freshwater Algae, vol. 16, 1996).