Phylum: Charophyta   Family: Desmidiaceae

Cosmarium praemorsum (L.A. de Brébisson), sensu W. & G.S. West 1908

First described and illustrated by Brébisson (1856: 128, pl. 1: 8). Brébisson’s original description and figure are poor so currently West & West’s (1908: 196) concept has been adopted by later authors. To save further confusion Kouwets (in manuscript) is proposing a new name for the West’s concept: C. confusopraemorsum, leaving the original form presented by De Brébisson (1856) as a species inquirenda. Chloroplast with two pyrenoids but occasionally with one.
Cell dimensions: L: 41-54 µm, B: 38-48 µm, Is: 13-16 µm; Th: 23-30 µm, L/B: 1.01-1.22.
Because of taxonomic confusion, its status is unclear. In the Outer Hebrides, it is infrequently recorded.

References: 
Brébisson, L. A. de (1856). Liste des Desmidiées, observées en Basse-Normandie.
Kouwets, F.A.C. (in manuscript). European Flora of the Desmid Genus Cosmarium.
West, W. & West, G.S. (1908). A Monograph of the British Desmidiaceae, Volume 3.