Genus: Cell body crescent in shape (long, curved, tapered at both ends); cross section rounded; cell wall smooth or with longitudinal lines, bands on the cell wall in some species; chloroplast laminae ridged and radially arranged, which makes cross section star-shaped; pyrenoids aligned or scattered (Illustrations of The Japanese Fresh-water Algae, 1977).
Species [var. acutum]: Cell body slightly curved, tapered at rear, L/W= 20-30; both termini broad circle; cell wall smooth, transparent; chloroplasts with 3-4 pyrenoids in each semi-cells; 90-(92-176) μm long, 4-(4.8-8.4) μm wide (Illustrations of The Japanese Fresh-water Algae, 1977).
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var. acutum
110-130 x 4 μm
L/W=28-33
Komado marsh
Showa and Tajima
Fukushima, 2004
var. acutum ?
110 x 4.3 μm
L/W=23.4
Hiroshima, 1998
Movies 
var. variabile
122 x 4 μm
L/W=30.5
Yamagata, 1999
var. variabile ?
130 x 3 μm
L/W=43.3
Ishikawa, 2000
var. variabile ?
80 x 2.5 μm
L/W=32
Shikinawa-ike
Fukuoka, 2001
var. variabile ?
μm
L/W=
Chiba-Minato Park
Chiba, 2003
var. variabile ?
178 x 5 μm
L/W=35.6
Mizumoto Park
Tokyo, 2001
var. variabile ?
195 x 5 μm
L/W=38
Mizumoto Park
Tokyo, 2001
var. variabile ?
130 x 4 μm
L/W=32.5
Chaya-numa p.
Fukushima city
Fukushima, 2005
var. variabile ?
μm
L/W=
Higusa-numa
Hikari
Chiba, 2003
