Phylum: Charophyta Family: Desmidiaceae
Staurastrum cristatum var. oligacanthum (Brébisson ex W. Archer) Coesel & Meesters
Differs from the nominate in having short slightly open sinuses before becoming wide open. The lateral angles are markedly produced. The varietal name means little or few spines. Distribution in the Outer Hebrides is unknown but likely to be rare
References:
Coesel, P.F.M. & Meesters, K.J. (2013) European Flora of the Desmid Genera Staurastrum and Staurodesmus