Phylum: Charophyta   Family: Desmidiaceae

Staurodesmus dejectus  (L.A. de Brébisson ex J. Ralfs) E. Teiling 1967

First described by Brébisson in Ralfs (1848: 121, pl. 20: 5) as Staurastrum dejectum. It was later moved by Teiling (1954: 128) to its current genus.
Cell dimensions: L: 22-30 µm; B: 21-33 µm; Is: 6-7.7 µm; Sp: 3-13 µm; Overall LxB: 28-45 x 30-53.
Common in fairly acidic to mildly alkaline waters such as the plankton of lochs and moorland bogs and pools.

References: 
Brébisson, L.A. de [in] Ralfs, J. (1848). The British Desmidieae.
Coesel, P.F.M. & Meesters, K.J. (2013). European Flora of the Desmid Genera Staurastrum and Staurodesmus.
John, D.M. & Williamson, D.B(2009). A Practical Guide to the Desmids of the West of Ireland.
Teiling, E. (1954). l'Authentique Staurodesmus dejectus (Bréb.).