Phylum: Charophyta   Family: Desmidiaceae

Xanthidium antilopaeum F.T. Kützing 1849

First described by Kützing (1849: 177) surprisingly without illustration. A variable species that has spawned numerous infraspecific taxa.
Cell dimensions: L: 42-76 µm; B: 42-72 µm; Is: 13-20 µm; Sp: 8-19 µm; Overall LxB: 54-90 x 57-90 µm.
A common desmid found in variously acidic waters such as loch-margins and moorland pools.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.
Kützing, F.T. (1849). Species algarum.
West, W. & West, G.S. (1912). A Monograph of the British Desmidiaceae, Volume 4.