Phylum: Charophyta   Family: Desmidiaceae

Cosmarium venustulum F.A.C. Kouwets 2025

A recently described small desmid based on poorly described small forms of C. venustum. (Brébisson) W. Archer 1861. It needs to be compared with similar small taxa such as C. subregnellii Kouwets 2025.
Single cell dimensions: L: 13.3 µm; B: 10.2 µm.; Is: 3.1 µm; Th: 7 µm; L/B: 1.31.
The status is unknown in the Outer Hebrides due to earlier taxonomic confusion. The current find is from semi-permanent rainwater pools in a disused quarry, which are slightly acidic to slightly alkaline.

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