Phylum: Charophyta Family: Desmidiaceae
Staurastrum scabrum Brébisson
An acidophile with an Arctic/boreal distribution. Found in oligotrophic bogs and moorland pools. Said to be quite common but data lacking for the Outer Hebrides
References:
Coesel, P.F.M. & Meesters, K.J. (2013) European Flora of the Desmid Genera Staurastrum and Staurodesmus
John, D.M. & Williamson, D.B. (2009) A Practical Guide to the Desmids of the West of Ireland