Genus: Unicellular; variable in shape; a constriction at the center of the cell body; mostly longer than wide; flattened; each semicell hemispherical, spherical, ellipsoidal, rectangular, pyramidal or kidney-shaped; no apical indentation (Illustrations of The Japanese Fresh-water Algae, 1977). Species: Cell body rectangular, 53-90 μm long, 47.6-85 μm wide; isthmus 19-30 μm wide; semicells subrectangular, with rounded corners; side view nearly circular; apical view elongated ellipsoidal; marginal granules 34-37 in number (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