Phylum: Charophyta   Family: Desmidiaceae

Staurodesmus ralfsii (W. West) G.H. Tomaszewicz 1988

Cells are similar in face view to Std. glaber but are 2-radiate and often have a slightly elongate isthmus.
Cell dimensions: L: 19-23 µm; B: 16-19 µm; Is: 5-7.5 µm; Sp: 4-10 µm; Overall B: 28-40.
A scarce acidophile of little-known distribution. Current finds have been from shallow moorland pools and bogs. In a European context, it has an Atlantic distribution.

References: 
Coesel, P.F.M. & Meesters, K.J. (2013). European Flora of the Desmid Genera Staurastrum and Staurodesmus.
Van Westen, M.C. (2024). Sieralgen in Drenthe.