Subgenus: Cell body cylindrical or dumbbell-shaped, dorso-ventrally not compressed, transverse section circular. Section [ Eudysphinctium ]: Cell body dumbbell-shaped, constriction strong, cell surface smooth, dotted or punctated (Illustrations of The Japanese Fresh-water Algae, 1977). Species:

31 μm 63 μm 94 μm; x 640

Images of collecting locality: Kareki-numa marsh, Nikko city (formerly Fujiwara town), Tochigi Pref., Japan, August 2, 2008 by Eizaburo Tsukii