Phylum: Charophyta   Family: Desmidiaceae

Tetmemorus flensburgii M. van Westen 2015

First described and illustrated by Flensburg 1967: 70; pl. I: d) as Tetmemorus brebissonii var. intermedius. He made the astute observation: “It appears to be morphologically well delimited from both the main species and var. minor, but it differs from these above all by its extreme ecological requirements.” More recently, Van Westen (2015: 237, figs. 33,34,36-41) decided it was sufficiently distinct to warrant species rank.
Cell dimensions: L: 100-130 µm; B: 19-29 µm; Is: 16-22 µm; L/B: 4.3-6.2.
This intermediate-sized taxon occupies a distinctly acidic habitat, unlike the nominate variety. In the Outer Hebrides, it is common, especially with Sphagnum.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition) Desmids of the Lowlands.
Flensburg, T. (1967) Desmids and other benthic algae of lake Kävsjön and Store Mosse, SW Sweden.
Van Westen, M. (2015) Taxonomic notes on desmids from the Netherlands.