Phylum: Charophyta   Family: Desmidiaceae

Euastrum biscrobiculatum (J. Woloszynska) P.F.M. Coesel 2007

First described by Woloszynska (1950) as Euastrum bipapillatum f. biscrobiculata. After considerable debate as to its true affinity, Coesel (2007) has raised it to species rank, “… because of the occurrence of two deep grooves in the semicell wall (when observed in frontal view) converging from semicell base to semicell apex. These grooves are clearly figured in Woloszynska's … illustrations and appear to be consistently present in Dutch material investigated.”
Cell dimensions: L: 24-35 µm; B: 17-28 µm; Is: 6.0-7.5 µm; Th: ?; L/B: 1.23-1.50.
Very similar to other Euastrum species and often it is necessary to look at the cell-wall structure to make an identification. Because of possible misidentifications in the past, its distribution in the Outer Hebrides is uncertain.

References: 
Coesel, P.F.M. (2007). Taxonomic notes on Dutch desmids IV: new species, new names, new combinations.
Coesel, P.F.M. & Meesters, K.J. (2023 second edition) Desmids of the Lowlands.
Woloszynska, J. (1950) De Desmidiaceis fossilibus quae in Roztoki ad Jaslo inventae sunt. 1.