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 slightly longer than width, bay linear, both side separated, bay opening wide, 56 μm long, 50.4 μm wide, isthmus 16.8 μm wide; semicells ellipsoidal or reniform, each corner broadly rounded, apex slightly convex; cell wall covered with granules arranging in horizontal rows at the center of semicells, slightly radial at the periphery (Illustrations of The Japanese Fresh-water Algae, 1977).

31 μm 63 μm 94 μm; x 640

Images of collecting locality: No.11, Kannon-numa Forest Park (pond/marsh), Shimogo town, Fukushima Pref., Japan, November 15, 2008, by Y. Tsukii