Phylum: Charophyta   Family: Desmidiaceae

Cosmarium pseudowillei F.A.C. Kouwets 2025

This recently described species was part of the Cosmarium quadratum Ralfs 1848 complex. It’s similar in size to that species but is mainly distinguished by its closed sinus for most of its length and being thick-walled.
Single cell dimensions: L: 66.1µm; B: 38.4 µm; Is: 17.4 µm; Th: c.20 µm; L/B: 1.73.
Because of the foregoing the status is uncertain. From the little data available it would seem to prefer acidic waters such as peat bogs and moorland pools

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