Phylum: Charophyta   Family: Desmidiaceae

Cosmarium fontigenum C.F.O. Nordstedt 1878

A characteristic species with the upper sides and apex faintly undulate.
Cell dimensions: L: 22-26 µm, B: 22-27 µm, Is. 6.5-9 µm; Th. 12-14 µm L/B: 0.95-1.04.
Frequently found in circumneutral waters such as lochs, moorland pools and abandoned peat-cuttings.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.
Kouwets, F.A.C. (2025). European Flora of the Desmid Genus Cosmarium.
Van Westen, M.C. (2024). Sieralgen in Drenthe.