Phylum: Charophyta   Family: Desmidiaceae

Xanthidium basidentatum (F. Børgesen) P.F.M. Coesel 1993

A large cell with a closed sinus and dilate apex. Semicells are elliptic to subreniform with the circumference well supported with medium spines. The apex is truncate but often with a saddle. The central protuberance is encircled with small granules. A characteristic feature is a small cluster of granules at the basal angles.
Cell dimensions: L: 66-75 µm; B: 63-71 µm; Is: 24-27 µm; Sp: 6-11 µm; Overall LxB: 85-89 x 76-86 µm.
A rare desmid found in Sphagnum bogs and moorland peaty pools. West & West (1912: 80) only record two sites in Scotland.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.
Van Westen, M.C. (2024). Sieralgen in Drenthe.
West, W. & West, G.S. (1912). A Monograph of the British Desmidiaceae, Volume 4.