Phylum: Charophyta   Family: Desmidiaceae

Staurastrum echinatum Brébisson ex Ralfs

An acidophile that is widespread in Europe but not proving common in the Outer Hebrides, although it can be locally abundant. Mainly reported as a triradiate species, the population from Benbecula (NF8396 4791) was predominantly quadriradiate. I'm grateful to Marien van Westen for the identification from this sample

References: 
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