Phylum: Charophyta   Family: Desmidiaecea

Staurastrum haaboeliense N. Wille 1880

The original illustration by Wille (1880 [1881], p. 42, pl. 2: 27) is rather primitive and it’s better to defer to West, West & Carter (1923, p. 140, pl. 142: 19-20) for a better concept. However, their remark regarding the processes: “… tipped with a group of tiny spines …” is not reflected in their drawing. Prescott et al. (2001, p. 218, pl. 401: 12) describes the processes “… tipped with 2 teeth …” [µm] while his drawing has at least three. Observations from the Outer Hebrides show four medium spines at the processes’ tips. It is described as an Arctic-alpine species with records from northern Europe and North America. West, West & Carter (l.c.) give three sites for Britain but none for Scotland. It would seem to be a rare British species. Mostly triradiate but Lenzenweger (1997, p. 93, pl. 29: 8) gives a quadri-radiate cell with larger dimensions.
Cell dimensions: L: 15-22 µm; B: 22-35 µm; Is: 6-8 µm.
Found in acidic habitats such a moorland pools and abandoned peat-cuttings.

References: 
Coesel, P.F.M. & Meesters, K.J. (2013). European Flora of the Desmid Genera Staurastrum and Staurodesmus.
Lenzenweger, R. (1997). Desmidiaceenflora von Österreich, Teil 2.
Prescott, W.G., et al. (2001 reprint). A Synopsis of North American Desmids. Part II, Desmidiaceae: Placodermae, Section 4.
West, W., West, G.S. & Carter, N. (1923). A Monograph of the British Desmidiaceae, Volume 5.
Wille, N. (1881). Bidrag til kundskaben om Norges ferskvandsalger 1. Smaalenenes Chlorophyllophyceer.