Phylum: Chlorophyta   Family: Selenestraceae

Ankistrodesmus spiralis  (W.B. Turner) Lemmermann

Most common in the British Isles towards the Scottish north-west. Tolerant of acidic and more circumneutral waters

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