Subgenus: Atomum (Apical area slightly depressed) Section: Retusa (Cell body large; granulated dome(s) at the center of each semicell) Species: Cell body 56-76 μm long, 45-62 μm wide, L/W=, (Illustrations of The Japanese Fresh-water Algae, 1977).

31 μm 63 μm 94 μm; x 640

Images of collecting locality: A small pond near Yamakado marsh (Yamakado-Suigen-no-Mori), Nishi-Asai town, Shiga Pref., Japan, June 30, 2008, by Y. Tsukii