Phylum: Charophyta   Family: Desmidiaceae

Cosmarium kossinskajae F.A.C. Kouwets 2025

A reclassification of Kosinskaya’s original form (the two ‘ss’ in the epithet is presumably an early naming error). Apparently only known from the New Siberian Islands and Spitzbergen (see Kouwets 2025: 299).
Kouwets’ cell dimensions: L: 15.6-19.5 µm, B: 14.4-18 µm, Is: 4.8-6 µm; Th: 8.4-10 µm, L/B: 1.08-1.26.
Mine – single cell: L: 20.7 µm, B: 19.1 µm, Is: 7.2 µm; Th: 10.7 µm, L/B: 1.09.
The Outer Hebridean cell was found in a shallow, mesotrophic loch with aquatics. Clearly an Arctic-subarctic species.

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