Phylum: Charophyta   Family: Desmidiaceae

Staurodesmus glaber  (J. Ralfs) E. Teiling 1948

This taxon in predominantly 3-radiate with a truncate to slightly domed apex to the semicells and sharply convergent spines.
Cell dimensions: L: 18-23 µm; B: 17-22 µm; Is: 6-8 µm; Sp: 5-8 µm; Overall B: 29-37.
Zygospore dimensions: core: 20-21 µm; spines: 11-12 µm; overall: 41 µm.
Infrequently recorded in the Outer Hebrides from acidic moorland bogs, abandoned peat-cuttings, and vegetated loch-margins.

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