Species [var. moniliferum]: Cell body moderately curved, gradually attenuated toward ends, which are broadly rounded, inner margin slightly inflated in the middle, outer margin strongly convex, 204-384 μm long, 36-60 μm wide, L/W=4.6-8; chloroplasts with 4-6 longitudinal ridges and 4-7 pyrenoids in each semicell; cell wall smooth and colorless; zygospores ellipsoid with a smooth wall (Photomicrographs of the Freshwater Algae, vol. 7, 1987). Cell body 170-450 μm long, 28-72 μm wide, L/W=6-8 (Illustrations of The Japanese Fresh-water Algae, 1977). Species [var. concavum]: Cell body curved more than var. moniliferum, inner side nearly straight or slightly concaved, 187-372 μm long, 30-56 μm (Illustrations of The Japanese Fresh-water Algae, 1977). Similar species -->> C. ehrenbergii;

50 μm 100 μm 150 μm; x 400

* C. moniliferum (Bory) Ehrenberg var. moniliferum: 170-(235-384)-450 μm long, 28-(36-60)-72 μm wide; L/W = 6-8; cell body slightly curved; both termini broadly rounded; cell wall transparent, smooth; chloroplasts with about 4 ridges of laminae; pyrenoids arranged in a single line (Illustrations of The Japanese Fresh-water Algae, 1977).

C. moniliferum var. concavum Klebs: cell body curved more strongly than var. moniliferum; 187-(300-344)-372 μm long, 30-(39-45)-56 μm wide; cell wall transparent, smooth; chloroplasts with about 4 ridges of laminae; pyrenoids arranged in a single line (Illustrations of The Japanese Fresh-water Algae, 1977).

* C. ralfsii Brébisson var. ralfsii: 300-(375)-610 μm long, (30)-40-62 μm wide; L/W = 6-9; spindle-shaped cell slightly curved, swells at center, tapered at termini; cell wall brownish, 7-9 fine ridges within 10 μm; 6-9 pyrenoids in a half-cell arranged in a single line (Illustrations of The Japanese Fresh-water Algae, 1977).

C. ralfsii var. gracilius (Maskell) Krieger: Smaller and narrower than var. ralfsii; 140-(240)-242 μm long, 11-(14)-25 μm wide; (Illustrations of The Japanese Fresh-water Algae, 1977).

C. moniliferum (Bory) Ehrenberg var. moniliferum: 170-(235-384)-450 μm long, 28-(36-60)-72 μm wide; L/W = 6-8; cell body slightly curved; both termini broadly rounded; cell wall transparent, smooth; chloroplasts with about 4 ridges of laminae; pyrenoids arranged in a single line (Illustrations of The Japanese Fresh-water Algae, 1977).

C. moniliferum var. concavum Klebs: cell body curved more strongly than var. moniliferum; 187-(300-344)-372 μm long, 30-(39-45)-56 μm wide; cell wall transparent, smooth; chloroplasts with about 4 ridges of laminae; pyrenoids arranged in a single line (Illustrations of The Japanese Fresh-water Algae, 1977).