Species [ var. dianae ]: Cell body slightly curved, tapered toward both ends, truncated with slanted edges, small pores present at outside of both termini, inner side at center slightly convex, 150-380 μm long, 15-40 μm wide, L/W = 10-12; cell wall smooth; chloroplasts with 5-8 pyrenoids in each chloroplast (Illustrations of The Japanese Fresh-water Algae, 1977). [var. dianae] Cell body 160-323 μm long, 20-28 μm wide, L/W=8.3-12; chloroplasts with about 6 laminae; semicells with 4-8 pyrenoids (Photomicrographs of the Freshwater Algae, vol. 6, 1987). [var. arcuatum] Cell body 243-313 μm long, 17-24 μm wide, L/W=13-15; (Photomicrographs of the Freshwater Algae, vol. 9, 1989).

50 μm 100 μm 150 μm; x 400 : 31 μm 63 μm 94 μm; x 640