Phylum: Charophyta   Family: Desmidiaceae

Staurastrum brebissonii W. Archer 1861

First described and illustrated by Archer in Pritchard (1861: 739). Cells slightly broader than long to almost as broad as long. This taxon can be confused with the similar St. hirsutum, best separated by the apical view: almost straight-sided in hirsutum; concave in brebissonii.
Cell dimensions: L: 35-58 µm; B: 40-65 µm; Is: c.13 µm; L/B: 1.04-1.11.
This species occupies slightly acidic habitats in oligo-mesotrophic waters. Reportedly widespread but rarely recorded in the Outer Hebrides.

References: 
Archer, W. in Pritchard, A. (1861) A history of infusoria, including the Desmidiaceae and Diatomaceae, British and foreign.
Coesel, P.F.M. & Meesters, K.J. (2013) European Flora of the Desmid Genera Staurastrum and Staurodesmus.
West, W., West, G.S. & Carter, N. (1923) A Monograph of the British Desmidiaceae, Volume 5.