Phylum: Charophyta   Family: Desmidiaceae

Cosmarium humile  Nordstedt ex De Toni 1889

A small desmid with a broad basal part to the semicell, which, including the basal angle, is 3-undulate, and a narrower apical part with four intra-marginal granules, not counting the apical angles, which give a slight undulate appearance. Fairly common, in mildly acidic to neutral waters such as peaty pools, disused peat cuttings, and shallow lochs.

References: 
West, W. & West, G.S. (1908) A Monograph of the British Desmidiaceae, Volume 3.
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.