Phylum: Charophyta   Family: Desmidiaceae

Cosmarium variolatum P.M. Lundell 1871

A medium-sized cell with a closed sinus. Semicells are subpyramidate, which are thick-walled and densely scrobiculate. Chloroplast axile with one pyrenoid.
Cell dimensions (3): L: 33-35 µm; B: 19-21 µm; Is: 6-8 µm; Th: 14-16 µm; L/B: 1.65-1.70.
A widespread and common species in the Arctic-alpine regions of Europe. Found on the acidic side of neutral in oligo-mesotrophic habitats. West & West (1905: 203) record it from the Outer Hebrides but as a rare desmid.

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.