Phylum: Charophyta   Family: Desmidiaceae

Staurastrum furcatum L.A. de Brébisson 1856

First described by Brébisson (1856: 136). West, West & Carter (2023: 173) describe it as generally distributed in Scotland but it's not proving common in the Outer Hebrides.
Cell dimensions: L. 25-39 µm, B. 20-40 µm, Is. 9-11 µm.
An acidophile that is widespread in Europe .

References: 
de Brébisson, L.A. (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. & Carter, N. (1923). A Monograph of the British Desmidiaceae, Volume 5.