Subgenus [ Eucosmarium ]: Cell body dorso-ventrally compressed, with strong constriction at the center, transverse section elliptical or diamond-shaped.
Section [ Cyclidium ]: Cell surface smooth; semicells half circle, half ellipsoid (Illustrations of The Japanese Fresh-water Algae, 1977).
Species [ var. circulare ]: Cell body large, nearly circular or slightly broad elliptical in shape, (51-75)-95 μm long, 48-90 μm wide, isthmus 20-(22-28)-34 &3956;m wide; semicells semicircular, basal corner rounded, side view ovoid or nearly circular, apical view elongated elliptical; cell wall covered with small dots; chloroplasts with 2 pyrenoids.
[ f. minor ]: Cell body 33-35-(40) μm long, 35-(47) μm wide, isthmus 12-14-(17) μm wide (Illustrations of The Japanese Fresh-water Algae, 1977).
Google Image Search
C. circulare
var. circulare ?
52 x 56 μm
Higashi-sano
Hakuba
Nagano, 2004
C. circulare
var. circulare ?
50 x 46 μm
Uruguay, 1999
C. circulare
f. minor ?
45 x 51 μm
Uruguay, 1999
C. circulare
f. minor ?
43 x 49 μm
Tane-ike
Togakushi highland
Nagano, 2005
