Phylum: Charophyta   Family: Desmidiaceae

Staurastrum acutum L.A. de Brébisson 1856

First described and illustrated by Brébisson (1856: 143, pl. 1: 26). West & West (1912: 190, pl. 128: 14) as St. granulosum var. acutum give Loch Mhor Bharabhais, Isle of Lewis, as a site. The rather similar St. granulosum is not mentioned in Coesel & Meesters (2013).
Cell dimensions: L: 28-32 µm; B: 28-33 µm; Is: 12-15.5 µm; L/B: 0.98-1.04.
In Britain it has a largely Scottish distribution, where it is reported as not uncommon. However, it is proving scarce in the Outer Hebrides. Found in the benthic and planktonic zones in mesotrophic waters.

References: 
Brébisson, L.A. de (1856) Liste des Desmidiées, observées en Basse-Normandie.
Coesel, P.F.M. & Meesters, K.J. (2013) European Flora of the Desmid Genera Staurastrum and Staurodesmus.
West, W. & West, G.S. (1912) A Monograph of the British Desmidiaceae, Volume 4.