Phylum: Charophyta   Family: Desmidiacea

Staurastrum bullardii G.M. Smith 1924

First described and illustrated by Smith (1924: 91, pl. 74: 19-23; pl. 75: 1-3) who dedicated the species to his colleague Charles Bullard. Smith’s original finds from Wisconsin, North America were tri-radiate. Skuja (176; pl. 20: 4) also found tri-radiate cells in Sweden. Teiling (213, figs. 6-7) found a bi-radiate form in Sweden, which he described as var. alandicum. The substantial population from Lewis is composed entirely of quadri-radiate cells (hitherto, undescribed). They have the same bowl-shaped semicell in face-view with a truncate apex supporting two emarginate verrucae (best seen in apical view).
Cell dimensions: L: 54-62 µm; B: 61-90 µm; Is: 11.4-13.9 µm.
A very rare desmid; the Lewis populations were found in very acidic habitats, predominantly in open Sphagnum pools, but also in moorland lochs.

References: 
Coesel, P.F.M. & Meesters, K.J. (2013) European Flora of the Desmid Genera Staurastrum and Staurodesmus.
Smith, G.M.(1922) The phytoplankton of the Muskoka region, Ontario, Canada.
West, W. & West, G.S (1903) Scottish freshwater plankton. I.