* C. navicula (Brébisson) Lütkemüller: Cell body not curved spindle or boat in shape; 24-(35-84)-93 μm long, 8-(11-20)-22 μm wide; L/W = 3-4; a single chloroplast and 1 or 2 pyrenoids in each semicell (Illustrations of The Japanese Fresh-water Algae, 1977).
C. libellula Focke var. libellula: Similar to C. navucula (not curved spindle or boat in shape) but large; 170-(216-224)-450 μm long, 30-(42-48)-52 μm wide; L/W = 5-8; chloroplast with 8-12 ridges; 3-5 pyrenoids in each semicell (Illustrations of The Japanese Fresh-water Algae, 1977).
C. libellula var. intermedium (Roy et Bisset) G. S. West: Smaller than var. libellula; 75-(123-174) μm long, 15-(20-32)-36 μm wide; 3-4 pyrenoids in each semicell (Illustrations of The Japanese Fresh-water Algae, 1977).