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, 163-(190-350) μm long, 8-(8.4-13)-20 μm wide, L/W = 25-33; both termini broadly rounded (nearly truncated); cell wall transparent, smooth; 5-7 pyrenoids arranged in a single line (Illustrations of The Japanese Fresh-water Algae, 1977).