Pediastrum simplex (Meyen 1829) Lemmermann var. simplex: Colonies of 4, 8, 16, 32 cells with no intercellular space, cells 20-30 μm long, 6-15 μm wide (Illustrations of The Japanese Fresh-water Algae, 1977).
* Pediastrum simplex var. duodenarium (Bailey) Rabenhorst: Colonies of 4, 8, 16, 32 cells with large intercellular space, cells 15-25 μm long, 6-13 μm wide (Illustrations of The Japanese Fresh-water Algae, 1977).