C. lunula (Müller) Nitzsch var. lunula: 250-(430-552)-1000 μm long, 47-(73-89)-120 μm wide; cell body large, nearly straight; cell wall smooth; many chloroplasts with many pyrenoids (Illustrations of The Japanese Fresh-water Algae, 1977).
C. lunula var. biconvexum Schmidle: (455)-603 μm long, (85)-97-126 μm wide; cell body more or less curved (Illustrations of The Japanese Fresh-water Algae, 1977).