Phylum: Chlorophyta   Family: Chlamydomonadaceae

Sphaerellopsis fluviatilis (Stein) Pascher

Infrequently reported. Favoured sites are small ponds and pools

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