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:
(Illustrations of the Japanese fresh-water algae, 1977).
Cosmarium sp. (similar to C. hammeri Reinsch ),
cell body 47 μm long, 29 μm wide, isthmus 15 μm wide,
x 400, x 640, Riverside green land (near Tone river), Sawara city, Chiba Pref., Japan, October 11, 2004 by Y. Tsukii
31 μm
63 μm
94 μm; x 640
Cosmarium regnellii Will var. regnellii:
Cell body small, (14-18)-22 μm long, (11-16.8)-22 μm wide,
isthmus (11-16.8)-22 μm wide;
(Illustrations of the Japanese fresh-water algae, 1977).