Phylum: Charophyta   Family: Desmidiaceae

Cosmarium boeckii Wille 1880

Reportedly widespread in circumneutral waters such as loch-margins and pools but not proving common in the Outer Hebrides. The large central granules are variable but the supraisthmial granule is most prominent.

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
John, D.M. & Williamson, D.B. (2009) A Practical Guide to the Desmids of the West of Ireland
Kouwets, F.A.C. (in manuscript) European Flora of the Desmid Genus Cosmarium