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: Cell body slightly curved, inner-side nearly straight; L/W= 6-8; cell wall smooth, transparent; chloroplasts with 5-10 laminae; 6-8 pyrenoids in each semi-cell; 200- (240-400) -540 μm long, 28- (30-52) -79 μm wide (Illustrations of The Japanese Fresh-water Algae, 1977).

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