Phylum: Charophyta   Family: Desmidiaceae

Cosmarium sportella var. subnudum  West & G.S. West

This is proving to be rather scarce in the Outer Hebrides with records from shallow moorland pools and loch margins

References: 
West, W. & West, G.S. (1908) A Monograph of the British Desmidiaceae, Volume 3
John, D.M. & Williamson, D.B. (2009) A Practical Guide to the Desmids of the West of Ireland
Coesel, P.F.M. & Meesters, K.J. (2007) Mesotaeniaceae and Desmidiaceae of the European Lowlands