Phylum: Charophyta   Family: Desmidiaceae

Cosmarium pokornyanum (A. Grunow) W. & G.S. West 1900

A variable species both morphologically and in its size range. It need comparing with Cosmarium anceps Lundell 1871, which seems to be closely related.
Cell dimensions (2): L. 32.1-32.5 µm; B. 18.5-19.4 µm; Is. 10.4-11 µm; Th. 14.9 µm; L/B. 1.66-1.76.
A widespread but infrequently recorded species. In Europe it has been found with moss-cushions in spring bogs and with moss on dripping rocks. The Outer Hebridean finds have come from ephemeral, mesotrophic, slightly alkaline, floodwater.

References: 
Kouwets, F.A.C. (2025). European Flora of the Desmid Genus Cosmarium. Part 1: Text. Part 2: Plates.
West, W. & West, G.S. (1905). A Monograph of the British Desmidiaceae, Volume 2.