Species: 250-(396-576)-790 μm long, 25-(33-84) μm wide; cell body large, slightly curved; both termini tapered; pyrenoids 7-15 in each semicell (Illustrations of The Japanese Fresh-water Algae, 1977). Cell body slightly curved, gradually attenuated toward the truncated ends, which somewhat recurved due to the covexity of the inner margin near the ends; inner margin straight or slightly concave, outer margin convex, 300-500 μm long, 32-50 μm wide, L/W=9-14; cell wall smooth and colorless or sometimes delicately striated and yellowish-brown in color; chloroplasts with ridges containing 7-11 pyrenoids in central row (Photomicrographs of the Freshwater Algae, vol. 1, 1984).
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Cell body long (388-915 μm), central region nearly straight; L/W=15-33
var. elongatum
892 x 40 μm
L/W=22.3
Doman Green P.
Toda
Saitama, 2004
var. elongatum
860 x 41 μm
L/W=21.0
Doman Green P.
Toda
Saitama, 2004
var. elongatum
772 x 38 μm
L/W=20.3
Aizu Recreation p.
Aizuwakamatsu
Fukushima, 2005
var. elongatum
636 x 34 μm
L/W=18.7
Nogyo Fureai p.
Toride
Ibaraki, 2008
var. elongatum
720 x 40 μm
L/W=18
Junichogata s.p.
Himi
Toyama, 2006
var. elongatum
654 x 30 μm
L/W=21.8
Naruto-Togane
Sanmu
Chiba, 2006
var. elongatum
635 x 33 μm
388 x 19 μm
L/W=20, 19
Japan, 1998
var. elongatum
620 x 27 μm
L/W=23.0
Okubo Ryoke
Akigase park
Saitama, 2005
var. elongatum
620 x 27 μm
L/W=23.0
Jionji-shinsui-koen
Iwatsuki
Saitama, 2006
var. elongatum
550 x 38 μm
L/W=14.5
Imou bog
Toyohashi
Aichi, 2004
var. elongatum
303 x 20 μm
L/W=15
Motono
Chiba, 2003
var. elongatum
470 x 23.5 μm
L/W=20
Higusa-numa
Hikari
Chiba, 2003
var. elongatum
μm
L/W=
Kashiwa VMP
Kashiwa
Chiba, 2008
var. elongatum
490 x 28 μm
L/W=17.5
Yamato
Kanagawa, 2003
var. elongatum
410 x 18 μm
L/W=22.8
Michi-no-eki
Tsukiyono
Gunma, 2003
C. acerosum ?
480 μm
L/W=24
bands present
Japan, 1998Cell body less than 20 μm in width
C. acerosum ?
400 x 20 μm
L/W=20
Kosugi
Toyama, 2002
C. acerosum ?
388 x 16 μm
L/W=24
Higashi-Urawa
Saitama, 2001
C. acerosum ?
390 x 15 μm
L/W=26
Kosugi
Toyama, 2002
C. acerosum ?
305 x 18 μm
L/W=17
Furu-tone river
Kasukabe
Saitama, 2004
C. acerosum
270 x 18 μm
L/W=15
Kijioka Castle R.
Honjo (Kodama)
Saitama, 2006