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).
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