Phylum: Chlorophyta   Family: Scenedesmaceae

Desmodesmus armatus (Chodat) E.H. Hegewald

Widespread in the plankton of slightly nutrient-rich waters

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