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).
Subgenus [Euclosterium]: Cell body curved.
Species:
Google Image Search
C. turgidum
var. turgidum
562 x 43 μm
L/W=13
Japan, 1998
C. turgidum
var. turgidum
580 x 43 μm
L/W=13.5
Japan, 1998
C. turgidum
var. turgidum
720 x 54 μm
L/W=13.3
Ukima Park
Kita/Itabashi
Tokyo, 2006
C. turgidum
var. borgei ?
270 x 18 μm
L/W=15
USA, 1999
C. turgidum
var. borgei
785 x 46 μm
L/W=17
band at center
Hiroshima, 1998
Movies 
C. turgidum
var. borgei
775 x 46 μm
L/W=17
band at center
Japan, 1998
C. turgidum
var. turgidum
760 x 48 μm
L/W=15.8
Kashibaru m.4
Karatsu
Saga, 2008
