Species [ var. pseudoexiguum ]: Cell body small, L/W=2 or more, with deep constriction; semicells nearly rectangle in shape; apex and lateral margins slightly convexed; 18-25 μm long, 10-13.6 μm wide, isthmus 2-4 μm wide. [ var. retusum Hirano ] Semicells trapezoid in shape; lateral margins nearly straight, narrowed toward apex; anterior half of the margins slanted and slightly concaved; 22-23 μm long, 12-13 μm wide, isthmus 3.4 μm wide. [ var. hexagonum Grönblad ] Semicells hexagonal in shape, broadened toward apex; 18-19.6 μm long, 10.7-12.6 μm wide, isthmus 3-4.3 μm wide.

Similar species --> > C. succisum;

31 μm 63 μm 94 μm; x 640

Cosmarium pseudoexiguum Raciborski var. pseudoexiguum, cell body μm long, μm wide, x 640, Omine-numa (pond/marsh), Tsukiyono town, Gunma Pref., Japan, September 2003 by Y. Tsukii
31 μm 63 μm 94 μm; x 640