Phylum: Charophyta   Family: Desmidiaceae

Staurastrum laevispinum J.P. Bisset 1884

Semicells are 3-radiate in apical view. This nominate variety has entire ends (not bifurcate).
Cell dimensions: L: 20-35 µm; B: 30-45 µm; Is: 7.1-10.6 µm; L/B: 6-7.
A rare species belonging to the Arctic-alpine regions. Found in plankton and the benthic layer of shallow pools.

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.