Phylum: Charophyta   Family: Desmidiaceae

Cosmarium subcostatum Nordstedt

Found in circumneutral waters such as streams, shallow pools and disused peat-cuttings. Widespread but infrequently recorded

References: 
West, W. & West, G.S. (1908) A Monograph of the British Desmidiaceae, Volume 3
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