Phylum: Charophyta   Family: Desmidiaceae

Cosmarium cerdagnense F.A.C. Kouwets 2025

A recently described species named after the site where type material was collected: Cerdagne, eastern Pyrenees, France. Similar to C. subarctoum (Lagerheim) Raciborski 1892 but smaller than that species in all dimensions including the L/B ratio. This has, most likely, an Arctic-alpine distribution.
Cell dimensions: L: 15.3-18.5 µm, B: 13.2-16.5 µm, Is: 8.7-10.4 µm; Th: 9.5-11.1 µm, L/B: 1.06-1.16.
Of unknown status in Europe but presumed to be quite rare. The Outer Hebridean finds are from circumneutral, mesotrophic, waters.

References: 
Kouwets, F.A.C. (2025). European Flora of the Desmid Genus Cosmarium.