Phylum: Charophyta   Family: Desmidiaceae

Staurastrum borgeanum  W. Schmidle 1898

First described and illustrated by Schmidle (1898: 60, pl. 3: 7). West, West & Carter (1923: 129) regard this as a synonym of S. proboscideum but later researchers prefer to keep them separate. Coesel & Meesters (2013: 74 & 136) list them as separate species but their descriptions are identical apart from semicell-shape: “cup-shaped or subcuneate” for S. borgeanum; “broadly fusiform” for S. proboscideum.
Cell dimensions: L: 32-40 µm; B: 28-40 µm; Is: 10-13 µm.
A common species found in acidic, mesotrophic, waters such as moorland pools and bogs including with Sphagnum.

References: 
Coesel, P.F.M. & Meesters, K.J. (2013) European Flora of the Desmid Genera Staurastrum and Staurodesmus.
Schmidle, W. (1898) Über einige von Knut Bohlin in Pite Lappmark und Vesterbotten gesammelte Süsswasseralgen.
West, W., West, G.S. & Carter, N. (1923) A Monograph of the British Desmidiaceae, Volume 5.