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: 390-(430-580)-800 μm long, 4-(5-7)-8 μm wide, L/W = 73-135; cell body very long, slightly curved, tapered at both termini; cell wall transparent, lack bands (Illustrations of The Japanese Fresh-water Algae, 1977).

C. aciculare 2 clips μm Higashi-hiroshima Hiroshima, 1998

C. gracile ? 1 clip μm Higashi-hiroshima Hiroshima, 1998