Phylum: Charophyta   Family: Desmidiaceae

Staurodesmus subtriangularis   (O. Borge) Teiling

Thought to be common in acidic bogs and loch-margins, especially in the north-west

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
Tsarenko, P.M., Wasser, S.P. & Nevo, E. editors (2014) Algae of Ukraine, Volume 4: Charophyta