Phylum: Charophyta   Family: Desmidiaceae

Cosmarium annulatum var. elegans Nordstedt 1873

A rare desmid with an Arctic-alpine distribution, possibly with an Atlantic bias. Found in moorland pools and bogs; also on wet rocks. Even in ideal habitat, it's never abundant.

References: 
Kouwets, F.A.C. (in manuscript) European Flora of the Desmid Genus Cosmarium.
John, D.M. & Williamson, D.B. (2009) A Practical Guide to the Desmids of the West of Ireland.
West, W. & West, G.S. (1912) A Monograph of the British Desmidiaceae, Volume 4.