Phylum: Charophyta   Family: Desmidiaceae

Xanthidium cristatum J. Ralfs 1848

A medium-sized cell with six spines visible in face view that are about equally spaced around the semicell. One each at the basal, lateral and apical angles. The lateral and apical spines are paired. Similar to X. fasciculatum but that species has the central protuberances ornamented in the form of coronas (superficial in X. cristatum). Also, the lower spines are twinned in X. fasciculatum (single in X. cristatum).
Cell dimensions: L: 47-55 µm; B: 40-47 µm; Is: 14-16 µm; Sp: 8-16 µm; Overall LxB: 69-81 x 55-72 µm.
The British distribution is biased towards the north-west where it is found in the plankton of lochs but also upland pools. Infrequently found in the Outer Hebrides.

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.