Phylum: Charophyta   Family: Desmidiaceae

Staurastrum dispar L.A. de Brébisson 1856

Very similar to Staurastrum striatum but with the cells more fusiform, and the angles slightly more acute.
Cell dimensions: L. 24-37 µm, B. 23-38 µm, Is. 8-11 µm.
West & West (1912: 187) failed to find it. Roy & Bisset (1893-1894: 237) note: “Not common. Sutherland, Ross, Aberdeen, Kincardine, Forfar, Perth, Dumbarton. With zygospores, in Aberdeen, at Slewdrum.” Unfortunately, they failed to describe or illustrate the zygospores. This is a rare taxon in the Outer Hebrides, found in clear-water ditches and similar ephemeral waters; also in cattle water troughs.

References: 
Coesel, P.F.M. & Meesters, K.J. (2013). European Flora of the Desmid Genera Staurastrum and Staurodesmus.
Roy, J. & Bisset, J.P. (1893-94). On Scottish Desmidieae.
Van Westen, M.C. (2024). Sieralgen in Drenthe.
West, W. & West, G.S. (1912). A Monograph of the British Desmidiaceae, Volume 4.