Species [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.
[ var. intermedium ]: Smaller than var. libellula; 75-(123-174) μm long, 15-(20-32)-36 μm wide; 3-4 pyrenoids in each semicell.
[var. interruptum]: Smaller than var. libellula, 90-(150-271)-400 μm long, 16-(25-31)-55 μm wide; chloroplast in each semicell separated into two pieces (Illustrations of The Japanese Fresh-water Algae, 1977).

C. libellula 2 clips 108 x 20 μm L/W=5 2 pyrenoids Higashi-hiroshima Hiroshima, 1998