Phylum: Charophyta   Family: Desmidiaceae

Euastrum insigne J. Ralfs 1848

Semicell basal portion broadly deltoid, upper portion inversely deltoid. Sinus widely open, ‘v’-shaped. Basal angles protracted to a blunt point, above that is a slightly raised section, almost a sub-lobe, then a long incurvation to the apical angles. Apex truncate with a closed median incision. Within each basal angle is a large, downward-pointing protuberance. Cell-wall with marked pore-fields, at the end of the angles often granulated by secreted material.
Cell dimensions: L: 100-130 µm; B: 50-75 µm; Is: 13-18 µm; Th: 32-36 µm; L/B: 1.70-2.00. An acidophile of boggy habitats and shallow vegetated lochs. A Europe-wide rare species but, interestingly, West & West (1905: 25) say "… but often occurs in great abundance in the west of Scotland, the Outer Hebrides, and the west of Ireland." Recent studies suggest this is no longer the case

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition) Desmids of the Lowlands.
Ralfs, J. (1848) The British Desmidieae.
Ruzicka, J. (1981) Die Desmidiaceen Mitteleuropas, Volume 1, Part 2.
West, W. & West, G.S. (1905) A Monograph of the British Desmidiaceae, Volume 2.