Phylum: Charophyta   Family: Desmidiaceae

Staurodesmus cuspidatus var. divergens (C.F.O. Nordstedt) P.F.M. Coesel 2007

Semicells bowl-shaped from an elongated isthmus. Spines at the apical angles divergent, apex truncate to slightly convex. A triradiate taxon. This taxon was made a forma by Teiling (1967: 533) and later raised to varietal status by Coesel (2007: 10). However, in their Desmids of the Lowlands, Coesel & Meesters (2023: 201, Pl. 100: 1-16) decided that Std. cuspidatus is such a variable species they no longer recognised var. divergens as a separate taxon. Looking at the 16 figures on their plate 100, there is not a convincing image of truly divergent spines. I believe this is still a separate taxon and refer you to Teiling (l.c., pl. 9: 15 – reproduced below), which depicts the salient points of the taxon and is rather similar to the Outer Hebridean cell. More finds are awaited to get a better understanding.
Single cell dimensions: L: 28.8 µm; B: 27.9 µm.; Is: 7.1 µm; Sp: 8-9; Overall LxB: 41 x 39 µm.
The single Outer Hebridean find was from an acidic, mesotrophic, vegetated loch.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.
Teiling, E. (1967). The Desmid Genus Staurodesmus. A taxonomic study.