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 [var. acutum]: Cell body slightly curved, tapered at rear, L/W= 20-30; both termini broad circle; cell wall smooth, transparent; chloroplasts with 3-4 pyrenoids in each semi-cells; 90-(92-176) μm long, 4-(4.8-8.4) μm wide (Illustrations of The Japanese Fresh-water Algae, 1977).