Genus: Cell body small, length = width, strong constriction at its center; semicells inverted triangular, ellipsoidal, rectangular, etc. in shape; straight or slightly curved spiny projections at each corner; one pyrenoid in each semicell; cell wall smooth (Illustrations of The Japanese Fresh-water Algae, 1977).

A. incus x 640	A. sublatus x 640	Arthrodesmus sp. x 640