Species [var. pseudopyramidatum]: Cell body medium in size, 42-61 μm long, 25-41 μm wide, L/W=1.8, isthmus 12.5-14 μm wide; semicells pyramidal or semielliptical in shape with flattened apex, basal corners rounded, lateral margins convex; a single chloroplast in each semicell. [var. stenonotum Nordstedt f. minor Raciborski]: Cell body small, 28-42 μm long, 24-25 μm wide, isthmus 10-11 μm wide. [var. carniolicum Lütkemüller]: Cell body 46-59 μm long, 29-34 μm wide, L/W=1.5, isthmus 12.6-14 μm wide; lateral margins concave (Illustrations of The Japanese Fresh-water Algae, 1977).

31 μm 63 μm 94 μm; x 640

Cosmarium pseudopyramidatum Lundell var. pseudopyramidatum, cell body 53 μm long, 29 μm wide, isthmus 14 μm wide, x 640, Omine-numa (pond/marsh), Tsukiyono town, Gunma Pref., Japan, September 2003 by Y. Tsukii