Phylum: Charophyta   Family: Desmidiaceae

Cosmarium boitierense F.A.C. Kouwets 1998

A variable species in outline shape with the broadest part of the semicells just below the median line. Named after Étang de la Boitière, Courmemin. The variety inambitiosum Kouwets 1998 differs only in being smaller with dimensions that don’t overlap with the nominate variety, according to Kouwets’ measurements. The central protuberance can be quite pronounced to almost lacking, which has a measured effect on the thickness of the cells.
Cell dimensions: L: 15.8-20.2 µm; B: 14.2-18.3 µm; Is: 4.6-5.8 µm; Th: 8.5-15.2; L/B:1.07-1.26.
Found in oligo-mesotrophic environments that are circumneutral. The Outer Hebridean finds have all come from ephemeral winter floodplains that dry out in the late spring..

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