Phylum: Charophyta Family: Desmidiaceae
Cosmarium clepsydra Nordstedt
Widespread but not common. A variable speices which has spawned numerous varieties over time. The Loch a' Bhursta cells have a distinct peaked apex a bit like a Chinaman's hat, and an open sinus
References:
Kouwets, F.A.C. (in manuscript) European Flora of the Desmid Genus Cosmarium
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