Phylum: Charophyta   Family: Desmidiaceae

Cosmarium quadratulum var. boldtii (E. Messikommer) W. Krieger & J. Gerloff 1965

First described and illustrated by Messikommer (1929: 153, pl. 1: 6) as Cosmarium norimbergense f. boldtii. It was later moved to its current position by Krieger & Gerloff (1965: 190, pl. 37: 11). There is ongoing research into these small desmids by Kouwets (in manuscript).
Cell dimensions: L: 8.0-11.8 µm, B: 8.5-11.0 µm, Is: 2-3 µm; Th: 4-7.5 µm, L/B: 1.02-1.16.
Status unknown in the Outer Hebrides due to frequent misidentifications. Found in slightly acidic pools and lochans.

References: 
Krieger, W. & Gerloff, J. (1962-9). Die Gattung Cosmarium.
Kouwets, F.A.C. (in manuscript). European Flora of the Desmid Genus Cosmarium.
Messikommer, E. (1929). Beitrage zur Kenntnis der Algenflora des Kantons Zurich, IV Folge: Die Algenvegetation der Moore am Pfaffikersee.