Phylum: Chlorophyta   Family: Oocystaceae

Eremosphaera gigas (W. Archer) Fott & Kalina

Found in boggy moorland pools and ditches. Thought to be common

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