Genus: Cell body crescent in shape (long, curved, tapered at both ends); cross section rounded; cell wall smooth or with longitudinal lines, bands on the cell wall in some species; chloroplast laminae ridged and radially arranged, which makes cross section star-shaped; pyrenoids aligned or scattered (Illustrations of The Japanese Fresh-water Algae, 1977).
Species [ var. cornu]: Cell body slightly curved, tapered at both ends, but inner side at center straight, 95-160 μm long, 5-(7.8-13) μm wide, L/W = 16-17; cell wall smooth; chloroplasts with 3-4 pyrenoids (Illustrations of The Japanese Fresh-water Algae, 1977).

C. cornu 8 clips conjugation 175-188 x 13-14 μm Otawara Tochigi, 2000