Phylum: Charophyta   Family: Desmidiaceae

Cosmarium benedictum F. Ducellier 1919

Semicells almost quadrate at the base with a rounded apex. Sides and apex slightly undulate. Isthmus shallow and slightly open. Chloroplast axile with one large pyrenoid. It should be carefully compared with Cosmarium pericymatium C.F.O. Nordstedt 1875, which occupies similar habitats. The main difference is that the latter species has a more rounded outline.
Single cell dimensions: L: 43.1 µm, B: 24.2 µm, Is: 18.4 µm; L/B: 1.78.
A rare species found in habitats liable to periodic drying such as ephemeral pools and moss on wet rocks.

References: 
Kouwets, F.A.C. (2025). European Flora of the Desmid Genus Cosmarium.