Phylum: Charophyta   Family: Desmidiaceae

Xanthidium octocorne J. Ralfs 1848

A small cell with rectangular-trapeziform semicells. The isthmus is elongate giving wide-open sinuses. Side and apical angles almost mamillate and supporting straight spines. The lateral and apical margins between the spines are concave. The zygospore is globose with 6-8 simple spines visible in face-view.
Cell dimensions: L: 16-24 µm; B: 15-20 µm; Is: 4.5-6 µm; Sp: 6-12 µm; overall LxB: 29-45 x 25-40.
Zygospore: minus projections: 17-19 µm; overall: 28-32 µm.
Widespread and common in acidic moorland pools and lochs, especially with plankton.

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