Phylum: Charophyta   Family: Desmidiaceae

Cosmarium pseudoprotuberans O. Kirchner 1878

A rare species found in oligotrophic waters such as shallow lochans and moorland bogs. The sinus is shallowly open at the apex, becoming wide open. The rounded lateral angles exhibit some wall-thickening. The relatively thick wall of the cell has a series of pores.

References: 
Kouwets, F.A.C. (in manuscript) European Flora of the Desmid Genus Cosmarium
Coesel, P.F.M. & Meesters, K.J. (2007) Mesotaeniaceae and Desmidiaceae of the European Lowlands
West, W. & West, G.S. (1908) A Monograph of the British Desmidiaceae, Volume 3