Staurosirella stoksiana Van de Vijver, sp. nov., LM and SEM micrographs taken from an additional population (BR-4840, Bosbeek, Maaseik, Belgium) A–P LM pictures of valves in valve face view in decreasing length Q SEM external view of a complete frustule in girdle view showing the girdle structure and the mantle R, S SEM external view of two complete valves with focus on the apical pore field and the depressed headpole. Both valves bear a series of marginal spines T SEM internal view of a complete valve U, V Two SEM externals view of a complete, heteropolar valve lacking marginal spines. Scale bars: 10 µm.