Phylum: Charophyta   Family: Desmidiaceae

Staurodesmus incus  (J. Ralfs) E. Teiling 1967

The length of the spines varies but are usually quite long. They are mainly divergent but can be almost parallel.
Cell dimensions: L: 14-30 µm; B: 13-25 µm; Is: 6.7-9.2 µm; Sp: 10-33 µm; Overall LxB: 26-47 x 35-85.
Infrequently recorded in the Outer Hebrides. The habitat range is considerable, from acidic moorland bogs, abandoned peat-cuttings, and open deep lochs.

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.