|  Species [var. pachydermum]: 
Cell body 78-117 μm long, 60-87 μm wide, isthmus 25-34 μm wide, 
semicells semielliptical in shape, corners rounded. [var. aethiopicum W. et G.S. West ]: Semicells nearly half-circle; cellwall thin; 
cell body 64-107 μm long, 56-80 μm wide, isthmus 28-34 μm wide.
 [var. ellipticum Hinode ]: Semicells rectangular at base; curvature of lateral margins weak compared to var. pachydermum;  
cell body 94-100 μm long, 67-74 μm wide, isthmus 28-34 μm wide.
 [var. heptagonum Grönblad ]: Semicells irregular pentagon in shape; 
posterior half of lateral margins nearly straight; 
cell body 94-100 μm long, 67-74 μm wide, isthmus 28-34 μm wide 
(Illustrations of The Japanese Fresh-water Algae, 1977).
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