Phylum: Charophyta   Family: Desmidiaceae

Cosmarium monomazum var. polymazum Nordstedt

This variety is characterised by a row of three large protuberances and a supraisthmial tubercle. It would seem to be very scarce in the Outer Hebrides with finds to date coming from circumneutral waters, mainly in the plankton

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