Phylum: Charophyta   Family: Desmidiaceae

Cosmarium margaritatum (P. Lundell) J. Roy & Bisset 1886

Originally a variety of Cosmarium latum, Roy & Bisset (1886) raised this to species level with a rather sketchy description and drawing; later (1894) providing better clarification. A widespread species of mesotrophic, circumneutral waters, but never common.

References: 
Roy, J. & Bisset, J.P. (1886) Notes on Japanese desmids. - No. I
Roy, J. & Bisset, J.P. (1894) On Scottish Desmidieae
Kouwets, F.A.C. (in manuscript) European Flora of the Desmid Genus Cosmarium