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 small, 16-(17-26.5) μm long, (10.5-14)-18 μm wide, isthmus 10-(10.5-14)-17 μm, L/W=1.25-1.5; semicells nearly spherical or inverted broad ovoidal; both ends broader than the center; apex slightly flat; cell wall smooth;
var. perminutum: 9-13.5 μm long, 5.6-8.5 μm wide, isthmus 6-7 μm, L/W=2; semicells inverted ovoidal; apex rounded (Illustrations of The Japanese Fresh-water Algae, 1977).