Phylum: Chlorophyra   Family: Oocystaceae

Willea irregularis  (Wille) Schmidle

Common in nutrient-poor pools and lochs in the plankton and detritus

References: 
John, D.M., Whitton, B.A. & Brook, A.J. (2011 second edition) The Freshwater Algal Flora of the British Isles