Phylum: Charophyta   Family: Desmidiaceae

Staurodesmus omearae (W. Archer) E. Teiling 1948

This is morphologically a quite variable taxon. Predominantly triradiate with a wide-open sinus. The sinus varies in breadth; shorter ones present a semicell as triangular; broader ones present the semicells and subrectangular, maybe representing two separate taxa. The spines also vary in length and are divergent.
Cell dimensions: L: 15-21 µm; B: 14-21 µm; Is: 5-9.2 µm; Sp: 5-15 µm; Overall LxB: 22-35 x 24-41.
A fairly common taxon, found in quite acidic to slightly alkaline conditions such as the larger lochs and shallow moorland pools.

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