Subgenus: Atomum (Apical area slightly depressed) Section: Retusa (Cell body large; granulated dome(s) at the center of each semicell ) Species: Cell body (73-95)-114 μm long, (65-77)-92 μm wide, constriction (14-21)-22 μm wide (Illustrations of The Japanese Fresh-water Algae, 1977).

31 μm 63 μm 94 μm; x 640

Images of collecting locality: Water field near Bungo-Mori railway station, Kusu town, Oita Pref., Japan, September 8, 2008 by Y. Tsukii