Phylum: Charophyta Family: Desmidiaceae
Staurastrum controversum var. semivestitum (West) Coesel
Only made a named variety in 1996 so little distribution data available for the Outer Hebrides. It has the same habitat requirements as the nominate
References:
Coesel, P.F.M. & Meesters, K.J. (2013) European Flora of the Desmid Genera Staurastrum and Staurodesmus