Phylum: Charophyta Family: Desmidiaceae
Staurastrum pelagicum West & G.S. West 1902
A very rare species in Britain with earlier records from Orkney, Shetland and Ireland. In the Outer Hebrides it is seldom recorded. It prefers circumneutral habitats, usually in the plankton. Some specimens have an extra spine at the end of the processes; a phenomenon with no taxanomic value.
References:
West, W., West, G.S. & Carter, N. (1923) A Monograph of the British Desmidiaceae, Volume 5
Coesel, P.F.M. & Meesters, K.J. (2013) European Flora of the Desmid Genera Staurastrum and Staurodesmus