Species: 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).