Phylum: Charophyta   Family: Desmidiaceae

Cosmarium pseudogaleritum  F.A.C. Kouwets 2025

This recently named species is based on British material described by West & West (1905: 194) under C. galeritum Nordstedt 1870. The semicells are rounded pyramidal with straight to slightly convex sides. The truncate apices are slightly rounded to slightly retuse. The chloroplast is axile with two pyrenoids.
Cell dimensions: L: 48-54 µm; B: 36-46 µm.; Is: 13-17 µm; Th: 22-25.6 µm; L/B: 1.23-1.38.
An infrequently recorded desmid, which, according to West & West (l.c.) is constantly found in upland areas, suggesting an Arctic-alpine distribution. Outer Hebridean finds have come from slightly acidic, mesotrophic waters.

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