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).