Phylum: Charophyta   Family: Desmidiaceae

Euastrum pectinatum  J. Ralfs 1848

Semicells in the basal part subrectangular and bilobed, apical part slightly convex with a hint of a central dip, extending into sub-rounded lobes. Between the two is a deep incurvation. A form exists that is almost devoid of lobes giving a rather plain outline. Just above the isthmus of the semicell is a large protuberance with two smaller ones either side. Two more appear in the upper part of the semicell. Chloroplast axile with a single pyrenoid. Zygospores have been found which are globose and subglobose, with conical mamillate projections.
Cell dimensions: L: 55-75 µm; B: 32-50 µm; Is: 9-14 µm; Th: 29-36 µm; L/B: 1.50-1.80. Zygospores: 45-70 µm.
Widespread and common in acidic moorland pools and bogs.

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.