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 concave, both ends broadly rounded, 140-(160-192) μm long, 14-(15-19.6) μm wide, L/W=8-12; cell wall smooth, transparent (Illustrations of The Japanese Fresh-water Algae, 1977).