Genus: Unicellular; variable in shape; a constriction at the center of the cell body;
mostly longer than wide; flattened; each semicell hemispherical, spherical, ellipsoidal,
rectangular, pyramidal or kidney-shaped; no apical indentation
(Illustrations of The Japanese Fresh-water Algae, 1977).
Species: Cell body large in size, 138-168 μm long, 73-90 μm wide, L/W=2; constriction 39-45 μm wide; semicells half-elliptical or ovoidal; cell wall dotted (Illustrations of the Japanese fresh-water algae, 1977).
Cosmarium turgidum Brébisson var. turgidum, stock Hnka-2,
cell body μm long, μm wide, L/W=, isthmus μm wide,
x 400, x 640, rice field, Higashi-sano (near Minami-kamishiro railway station), Hakuba village, Nagano Pref., Japan, October 3, 2004 by Y. Tsukii
50 μm 100 μm 150 μm; x 400 : 31 μm 63 μm 94 μm; x 640
Cell body 125 μm long, 60 μm wide, L/W=2.1, isthmus 50 μm wide, x 400, x 640