Phylum: Charophyta   Family: Desmidiaceae

Cosmarium subadoxiforme F.A.C. Kouwets 2025

This small desmid has semicells best described as depressed trapeziform. Sinus closed for the best part, lower half of sides broadly rounded and diverging, upper half of sides about straight and converging, apex truncate. The side and apical view presents a noticeable papilla, but this can be of variable size.
Single cell dimensions: L: 11.1 µm; B: 10.4 µm; Is: 3 µm; Th: 6.3 µm; L/B: 1.07.
Because of earlier taxonomic confusion, its status in the Outer Hebrides is unknown. European finds are from slightly acidic waters. The single Outer Hebridean find was from an acidic moorland bog with Sphagnum.

References: 
Kouwets, F.A.C. (2025). European Flora of the Desmid Genus Cosmarium. Part 1: Text. Part 2: Plates.