|  Species [ var. coarctatum ]: Cell body 24-33.3 μm long, 28-40 μm wide, 
L/W=, isthmus 6.5-9 μm wide; corners rounded, slightly curved upward; 
apex slightly concave. [ var. subcurtum Nordstedt ]: 
Cell body 20-28 μm long, 16-28.7 μm wide, 
L/W=, isthmus 5.5-12 μm wide 
(Illustrations of The Japanese Fresh-water Algae, 1977)
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