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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Inner side slightly concaved; L/W=7-14; more than 40 μm in width
Terminal angle Large
	var. acerosum 692 x 73 μm L/W=9.5 Koga general p. Koga Ibaraki, 2003	var. acerosum 560 x 49 μm L/W=11.4 Mizuko Fujimi Saitama, 2003	var. acerosum 532 x 52 μm L/W=10.2 Tachikawa Tokyo, 2001
var. acerosum 197-310 x 40-42 μm L/W=4.9-7.4 History and folk m. Tajima Fukushima, 2004	var. acerosum 290 x 38 μm L/W=7.6 Saitama, 1999	var. acerosum 442 x 45 μm L/W=9.8 Izumi-ya p.1 Midori-ku Chiba, 2007	var. acerosum ? 440 x 48 μm L/W= Iyari marsh Omachi Nagano, 2008
Terminal angle Medium
	var. acerosum 650 x 45 μm L/W=14 Uruguay, 1999	var. acerosum 620 x 43 μm L/W=14.4 Oyachi marsh Iizuna Highland Nagano, 2005	var. acerosum 575 x 43 μm L/W=13.4 a dividing cell ? Japan, 1998
var. acerosum 654 x 41 μm L/W=16.0 a dividing cell ? Kowashimizu Nagano, 2005	var. acerosum 575 x 43 μm L/W=13 Japan, 1998	var. acerosum 568 x 40 μm L/W=14.2 rice field Ichinoseki Iwate, 2005	var. acerosum ? 550 x 48 μm or C. turgidum ? Uruguay, 1999 Movies
var. acerosum 500 x 47 μm Ko-sumida river Kasukabe Saitama, 2006
var. acerosum μm L/W=15 Japan, 199?	var. acerosum 520 x 45 μm L/W=11.6 Zenko-ji Nagano, 2003	var. acerosum 506 x 42 μm L/W=12 Aquatic botanical g. Sawara Chiba, 2004	var. acerosum 488 x 43 μm 450 x 48 μm 400 x 40 μm Aeo Maruyama Park Saitama, 2002
var. acerosum 460 x 47 μm L/W=9.8 laminae irregular Inari Park Toyama, 2002	var. acerosum 450 x 42 μm L/W=10.7 Yamaguchi Univ. Yamaguchi, 2004	var. acerosum 436 x 46 μm L/W=9.5 Sanda Hyogo, 2001	var. acerosum 400 x 35 μm 300 x 40 μm L/W=11.4, 7.5 Saitama, 1999
var. acerosum 422 x 45 μm L/W=9.4 Asa-kawa Hachioji Tokyo, 2005	var. acerosum 373 x 39 μm L/W=9.6 Saitama, 2000	var. acerosum dividing cells Japan, 1999	var. acerosum ? 332 x 40 μm L/W=8.3 Japan, 1998
var. acerosum 197-310 x 40-42 μm L/W=4.9-7.4 Furuya-hongo Kawagoe Saitama, 2004	var. acerosum 305 x 44 μm L/W=6.9 Ranzan Saitama, 2004	var. acerosum 308 x 40 μm L/W=7.7 Aquatic botanical g. Sawara Chiba, 2004	var. acerosum 500 x 62 μm L/W=8.1 Numa-no-hara m. Madarao highland Niigata, 2005
Terminal angle Small
	var. acerosum ? 688 x 49 μm L/W=14 rice field Shinano Nagano, 2004	var. acerosum ? 510 x 42 μm L/W=12.1 Toyonodai park Otone Saitama, 2006	var. acerosum ? 490 x 40 μm L/W=12.9 Shimo-muneoka Shiki Saitama, 2004
var. acerosum ? 460 x 41 μm L/W=11.2 Oura central p. Oura Gunma, 2006	var. acerosum 384 x 44 μm L/W=8.7 Tsuki river Ogawa Saitama, 2007	var. acerosum ? 480 x 46 μm L/W=10.4 Toneri Park Adachi-ku Tokyo, 2005	var. acerosum ? 480 x 38 μm L/W=12.6 Japan, 1998
Terminal end Rectangular ?
var. acerosum 490 x 43 μm L/W=11.4 Koga Ibaraki, 2003

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