Phylum: Charophyta   Family: Desmidiaceae

Actinotaenium curtum (J. Ralfs) E.Teiling 1954

First described by Ralfs as Cosmarium cucurtum (1848: 109, pl. 33: 9). Later, Teiling (1954: 390, fig. 1) transferred it to Actinotaenium. Cells fusiform with a noticeable median indentation, apices narrowly rounded, apices with a minor indent, cell wall with fine pores.
Cell dimensions: L: 40-47 µm; B: 19-23 µm; L/B: 2.00-2.35.
Widespread but not common in circumneutral to mildly acidic waters, including ephemeral pools subject to desiccation.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.
Ralfs, J. (1848). The British Desmidieae.
Ruzicka, J. (1977). Die Desmidiaceen Mitteleuropas, Volume 1, Part 2.
Teiling, E. (1954). Actinotaenium, genus Desmidiacearum resuscitatum.