Phylum: Ochrophyta   Family: Ophiocytiaceae

Ophiocytium cochleare  (Eichwald) A.Braun

Probably common in the plankton of pools and lochs, especially on moorland

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