Phylum: Charophyta   Family: Desmidiaceae

Cosmarium bioculatum J. Ralfs 1848 sensu M.C. van Westen 2024

Following earlier confusion over this species, predating 1848, Ralfs (1848: 95) gave a more detailed description which should be regarded as the valid diagnosis of C. bioculatum. His cell dimensions (calculated from his fractions) are L: 17.9 µm; B: 14.3 µm; Is: 4.3 µm. The cells depicted here have the general characteristics of the species but are larger; they closely resemble those of Van Westen (2024: 393), which he considers most like an undescribed species. He draws attention to the striking chloroplast with finger-shaped extensions that reach the cell-wall. My images, where the chloroplast is visible, show a similar configuration.
Cell dimensions: L: 22-25.2 µm, B: 20-25 µm, Is: 7.8-9.5 µm; Th: c.11-12 µm, L/B: 0.95-1.15.
Found in slightly alkaline to mildly acidic habitats such as abandoned peat-cuttings.

References: 
Van Westen, M. (2024). Sieralgen in Drenthe.