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:
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C. rectimarginatum ?
218 x 20 μm
L/W=10.9
Kashibaru m.II
Karatsu
Saga, 2008
C. rectimarginatum ?
165 x 26 μm
L/W=6.3
3-4 pyrenoids
Higashi-hiroshima
Hiroshima, 1998
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C. rectimarginatum ?
122 x 11 μm
L/W=11.1
Kareki-numa
Nikko
Tochigi, 2008
C. rectimarginatum ?
110 x 10 μm
L/W=11.0
Omine-numa
Minakami
Gunma, 2007
C. rectimarginatum ?
106 x 10.5 μm
L/W=10.1
Ko-numa
Minakami
Gunma, 2008
