Phylum: Miozoa   Family: Ceratiaceae

Ceratium cornutum  (Ehrenberg) Claparède & J. Lachmann

Common in low nutrient waters such as the plankton of locks, bogs and pools

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