Phylum: Charophyta   Family: Desmidiaceae

Cosmarium praemorsum Brébisson

Widespread and common in weedy margins of lochs and bogs

References: 
Coesel, P.F.M. & Meesters, K.J. (2007) Mesotaeniaceae and Desmidiaceae of the European Lowlands
West, W. & West, G.S. (1908) A Monograph of the British Desmidiaceae, Volume 3
Kouwets, F.A.C. (1999) A check-list of desmids (Chlorophyta, Zygnemaphyceae) of France