Species: Cell body moderately curved, gradually attenuated toward ends, which are broadly rounded, inner margin slightly inflated in the middle, outer margin strongly convex, 204-384 μm long, 36-60 μm wide, L/W=4.6-8; chloroplasts with 4-6 longitudinal ridges and 4-7 pyrenoids in each semicell; cell wall smooth and colorless; zygospores ellipsoid with a smooth wall (Photomicrographs of the Freshwater Algae, vol. 7, 1987). Cell body 170-450 μm long, 28-72 μm wide, L/W=6-8 (Illustrations of The Japanese Fresh-water Algae, 1977).
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Similar species -->> C. dianae; C. leibleinii; C. ehrenbergii;
2) Cell body moderately curved; inner side concaved; L/W = 6-7; body > 300 μm
var. moniliferum
380 x 54 μm
L/W=7.0
Onnenai
Kushiro marsh
Hokkaido, 2005
var. moniliferum
340-360 x 55 μm
L/W=6.5
Numa-no-hara m.
Madarao highland
Niigata, 2005
var. moniliferum
340 x 50 μm
L/W=6.8
Oyomi marsh
Hakuba
Nagano, 2006
var. moniliferum
337 x 50 μm
L/W=6.7
Okubo-cho
Tomita
Ashikaga, 2003
var. moniliferum
320 x 50 μm
L/W=6.4
near Ayu-kawa b.
Fujioka
Gunma, 2004
var. moniliferum
316 x 47 μm
L/W=6.7
Kozai
Takamatsu
Kagawa, 2002
var. moniliferum ?
μm
L/W=
Watarase Wetland
Fujioka
Tochigi, 2005
var. moniliferum
304 x 47 μm
L/W=6.5
Kejo-numa 2
Osaki
Miyagi, 2006
var. moniliferum
305 x 52 μm
L/W=6.2
Shiba river
near Owada Park
Saitama, 2005
var. moniliferum
305 x 50 μm
L/W=6.1
Sannoh Park
Saitama
Saitama, 2005
var. moniliferum
303 x 50 μm
260 x 37 μm
L/W=7.0,6.1
near Karakemi m.
Omachi
Nagano, 2005
var. moniliferum
300 x 50 μm
L/W=6.0
Kodai-hasu p.
Gyoda
Saitama, 2006
var. moniliferum
330 x 50 μm
L/W=6.6
Karakemi marsh
Omachi
Nagano, 2008