Phylum: Charophyta   Family: Desmidiaceae

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

First described and illustrated by Børgesen (1889: 148, pl. 6: 11) as a variety of Xanthidium brebissonii. It was much later raised to species level by Coesel (1993: 109, pl. 2: 5). A characteristic feature is a small cluster of granules at the basal angles.
Cell dimensions: L: 60-75 µm; B: 54-67 µm; Is: 20-25 µm; Sp: 5-11 µm; Overall LxB: 76-90 x 68-83 µm.
A very rare desmid found in Sphagnum bogs and moorland peaty pools. West & West (1912: 80) only record two sites in Scotland.

References: 
Børgesen, F. (1889). Et lille Bidrag til Bornholms Desmidieflora.
Coesel, P.F.M. (1993). Taxonomic notes on Dutch desmids II.
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.
West, W. & West, G.S. (1912). A Monograph of the British Desmidiaceae, Volume 4.