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).

31 μm 63 μm 94 μm; x 640

Images of collecting locality: No.2, Chiba-Minato Park, Chiba City, Chiba Pref., Japan, January 27, 2008 by Y. Tsukii