Phylum: Charophyta   Family: Desmidiaceae

Staurastrum bulbosum var. cyathiforme  (West & G.S. West) Coesel & Meesters

The Wests (1923), as Staurastrum gracile var. cyathiforme, record it from Lewis in the plankton of lochs. This variety differs from the nominate in having pronounce apical teeth. Status in the Outer Hebrides uncertain

References: 
Coesel, P.F.M. & Meesters, K.J. (2013) European Flora of the Desmid Genera Staurastrum and Staurodesmus
West, W., West, G.S. & Carter, N. (1923) A Monograph of the British Desmidiaceae, Volume 5