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).
T=terminal; Tv=terminal vacuole

C. ehrenbergii	C. ehrenbergii ?	C. moniliferum
C. acerosum 550 x 48 μm	C. acerosum ? μm
C. aciculare ? 673 x 19 μm	Closterium sp. 292 x 14 μm	C. gracile x 640	Closterium sp. gracile ?
C. lanceolatum	C. lanceolatum ?	C. kuetzingii 383 x 16 μm	C. kuetzingii 300 x 16 μm