Phylum: Charophyta   Family: Desmidiaceae

Cosmarium bisphaericum Printz 1916

A rare desmid with probably an Arctic-alpine distribution. It is smaller than the variety densegranulatum, and larger than the similar species Cosmarium horizontale. It has a noticeably smaller isthmus. The most likely habitat is oligo-mesotrophic lochs and lochans, also boggy pools.

References: 
Printz, H. (1916) Beiträge zur Kenntnis der Chlorophyceen und ihrer Verbreitung in Norwegen.
Kouwets, F.A.C. (in manuscript) European Flora of the Desmid Genus Cosmarium.