Phylum: Charophyta   Family: Desmidiaceae

Staurastrum muticum L.A. de Brébisson ex J. Ralfs 1848

First described by Brébisson in Ralfs (1848: 125, pl. 21: 4 a-d; pl. 34: 13) and illustrated by Jenner. For a relatively small desmid, it experiences a considerable size-range, which made suggest a small species complex.
Cell dimensions: L: 15-45 µm; B: 15-40 µm; Is: 7-13 µm.
Infrequently recorded in the Outer Hebrides but may be overlooked. Found in the benthos of acidic habitats such as moorland pools and bogs.

References: 
Coesel, P.F.M. & Meesters, K.J. (2013). European Flora of the Desmid Genera Staurastrum and Staurodesmus.
Ralfs, J. (1848). The British Desmidieae.
West, W. & West, G.S. (1912). A Monograph of the British Desmidiaceae, Volume 4.