Phylum: Charophyta Family: Desmidiaceae
Cosmarium capitulum J. Roy & Bisset
The Wests (1908) record "The typical form of this species is not known to occur in the British Isles." Still little data to hand but thought to be rare. Found with loch-side vegetation in mildly acidic waters. A distinct shape with pronounced, rounded, lateral margins
References:
West, W. & West, G.S. (1908) A Monograph of the British Desmidiaceae, Volume 3
Coesel, P.F.M. & Meesters, K.J. (2007) Mesotaeniaceae and Desmidiaceae of the European Lowlands