Phylum: Charophyta   Family: Desmidiaceae

Cosmarium sparsipunctatum (W. Schmidle) W. & G.S. West 1897

A small, often amorphous, cell, similar to C. pseudarctoum Nordstedt 1879, but that taxon is larger.
Cell dimensions: L: 16.7-18.7 µm; B: 12.4-13.7 µm; Is: 10.7-11 µm; L/B: 1.27-1.48.
A rare desmid, possibly overlooked because of its size, occurs in atmophytic habitats such as mosses on wet rocks. The only sample from the Outer Hebrides came from squeezed bryophytes.

References: 
Kouwets, F.A.C. (2025). European Flora of the Desmid Genus Cosmarium.