Species [f. moniliforme]: Cell body 21-56 μm long, 11-29 μm wide, isthmus 4-11 μm wide, L/W=2; semicells spherical; cell wall smooth. [f. punctata Lagerheim ]: Cell wall dotted; 24-43 μm long, 14-25 μm wide. [f. elliptica Lagerheim ]: Cell body elongated, semicells broad ellipsoid in shape; 46-50 μm long, 28-32 μm wide. [f. supyriforme W. et G.S. West ]: Semicells inverted ovoid, apex slightly flatted; 34-56 μm long, 21-23 μm wide. [f. elongata W. et G.S. Wetst ]: Cell body 2 times longer than f. moniliforme, semicells ellipsoidal; 38-42 μm long, 17-22 μm wide. [f. pandriforme Heimerl ]: Smaller than f. moniliforme; 17.5-20 μm long, 10-15 μm wide (Illustrations of The Japanese Fresh-water Algae, 1977).

31 μm 63 μm 94 μm; x 640

Cosmarium moniliforme Turpin ex Ralfs f. moniliforme (or Cosmarium contractum f. jacobsenii ?), cell body 38 μm long, 23 μm wide, L/W=1.7, isthmus 6.5 μm wide, x 640, marsh pond No. 2, Iroha-numa (marsh/bog), Zao mountain, Yamagata city, Yamagata Pref., Japan, August 2, 2006 by Y. Tsukii

Cell body 37.5 μm long, 23.5 μm wide, L/W=1.6, isthmus 7 μm wide, x 640

Cell body 36.5 μm long, 24.5 μm wide, L/W=1.5, isthmus 7 μm wide, x 640

Images of collecting locality: No. 2, Iroha-numa (marsh/bog), Zao mountain, Yamagata city, Yamagata Pref., Japan, August 2, 2006 by Y. Tsukii