Phylum: Charophyta   Family: Desmidiaceae

Cosmarium pseudodentiferum F.A.C. Kouwets 2025

This large cell is broadly rounded with the sinus dilated at the isthmus. The more or less truncate apex has a central dent obvious in most cells. It is covered in small to medium granules with 32-36 visible on the periphery of each semicell.
Cell dimensions: L: 60-68 µm; B: 53-5-59 µm; Is: 21-22.5 µm; Th: 32-35 µm; L/B: 1.13-1.16.
A rare taxon with just one population found on the Outer Hebrides from moss on wet rocks. The European distribution suggests and Arctic-alpine preference.

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