Species [Ralfs f. quadratum]:
Cell body 48-(53-73) μm long, 25-(28-40) μm, isthmus 12-(20-26) μm wide,
L/W=2; bay opening closed; semicells rectangular, rounded at base with frontal slight depression; apical corners broadly rounded;
side view elliptical or oval; apical view elliptical; cellwall smooth.
[f. willei W. et G.S. West]
Cell body 50-(55-82) μm long, (30-36.5)-40 μm, isthmus 17-27 μm wide,
bay slightly opened; side margins of semicells nearly straight lacking slight depression at base
(Illustrations of The Japanese Fresh-water Algae, 1977).
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