Phylum: Charophyta   Family: Mesotaeniaceae

Netrium oblongum var. cylindricum West & G.S. West

Same habitat as the nominate variety. Cells are narrower and usually shorter than the type

References: 
Brook, A.J. & Williamson, D.B. (2010) A Monograph on some British Desmids
West, W. & West, G.S. (1904) A Monograph of the British Desmidiaceae, Volume 1