Phylum: Charophyta   Family: Desmidiaceae

Cosmarium neoregnellii F.A.C. Kouwets 2025

This recently described species is the largest of the C. regnellii complex. The main characteristics are lower sides straight and retuse, occasionally markedly so, upper sides convergent and retuse, apex truncate usually with a median dent and can appear undulate.
Cell dimensions: L: 15.1- 17.9 µm; B: 13.6-15.4 µm; Is: 4.8-6.3 µm; Th: 8.5-8.9 µm; L/B: 1.17-1.21.
Status in the Outer Hebrides is uncertain due to earlier taxonomic confusion. It would seem to prefer circumneutral waters such as loch-margins and deeper lochs, and moorland pools.

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