Phylum: Charophyta   Family: Desmidiaceae

Cosmocladium constrictum (W. Archer) W. Joshua 1883

Cells subcylindrical with a widely open sinus. Apical view almost cylindrical.
Cell dimensions: L: 13-18 µm; B: 7.8-12 µm; L/B: 1.7-1.84.
Found in mesotrophic, circumneutral waters such as loch-margins but rarely recorded.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.
Van Westen, M.C. (2024). Sieralgen in Drenthe