Phylum: Charophyta Family: Desmidiaceae
Staurastrum margaritaceum Menegh. ex Ralfs 1848
Widespread and common in marginal vegetation of lochs and in Sphagnum bogs. Also occasionally found with moss on wet rocks. Quite variable in the number of radial processes, with 4-6 being the most often found.
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.
John, D.M. & Williamson, D.B. (2009) A Practical Guide to the Desmids of the West of Ireland.