Species: Cell body medium in size, slightly curved, central region spindle-shaped, both side convex, both termini slightly swelled, with slanted edges (cf. C. ralfsii), 190-(320-400)-530 μm long, 18-(29-33) μm wide, L/W=11-16; cell wall striated (10 lines within 10 μm), brownish in color; chloroplasts with 3 laminae, 3-5 pyrenoids in each semicell (Illustrations of The Japanese Fresh-water Algae, 1977).

50 μm 100 μm 150 μm; x 400 : 31 μm 63 μm 94 μm; x 640

Images of collecting locality: No.1, Shimo-Kenashitai (marsh), Hakkoda mountain, Aomori city, Aomori Pref., Japan, September 13, 2006 by Y. Tsukii