Species [ var. depressum ]: Cell body small in size, wider than length, 33-50 μm long, (36.5-47.5)-50 μm wide, isthmus 10-15 μm wide; semicells depressed ellipsoid, with slightly flattened apex, side view circular, apical view elliptical, with a single pyrenoid. [ var. minor W. et G.S. West ]: Cell body smaller than var. depressum, 21-28 μm long, 21-25.3 μm wide, isthmus 4.3-8.4 μm wide; semicells elliptical diamond-shaped. [ var. achondrum (Boldt) W. et G.S. West ]: Cell body 36-51 μm long, 40-52 μm wide, L/W=1.0; isthmus 11-17 μm wide; semicells hexagonal ellipsoid, apex broad, flattened (Illustrations of The Japanese Fresh-water Algae, 1977).

Similar species -- >> C. bioculatum; C. contractum;

31 μm 63 μm 94 μm; x 640

Images of collecting locality: No.11, Kannon-numa Forest Park (pond/marsh), Shimogo town, Fukushima Pref., Japan, November 15, 2008, by Y. Tsukii