Most likely Licmophora flabellata (Greville) C.Agardh 1831. Will need confirmation with images of the valves.

Plate 9: figs 1-2. Boyer, C. S. (1916). Diatomaceae of Philadelphia and Vicinity. Lippincott, Philadelphia.

Hendey, N. I. (1964). An Introductory Account of the Smalller Algae of British Coastal Waters. Part V: Bacillariophyceae (Diatoms). Her Majesty’s Stationary Office. London. p. 168, Plate 26, fig. 5.

p. 113. Kraberg, A., Baumann, M., & Dürselen, C-D. (2010). Coastal Phytoplankton :
Photo Guide for Northern European Seas. p. 71. Verlag Dr. F. Pfeil. Munchen.

M.D. Guiry in Guiry, M.D. & Guiry, G.M. 2021. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 19 October 2021.