Phylum: Charophyta   Family: Desmidiaceae

Cosmarium pseudovalidius F.A.C. Kouwets 2025

This recently described species is intermediate between C. subspeciosum Nordstedt 1875 and C. validius (Nordstedt) Kouwets 2025. It’s a complex group that needs more finds to evaluate their taxonomic position.
Single cell dimensions: L: 65.6 µm; B: 53.6 µm; Is: 18.2 µm; L/B: 1.23.
Being newly described, the status in the Outer Hebrides is unknown. The only sample to date has come from the margins of a slightly alkaline loch.

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