Toxarium undulatum (all from Guam, GU44BJ-4) A, B entire valves in LM and SEM, respectively, showing prominent undulation C, D central expanded portion external and internal views, respectively, the latter showing costae E pole, internal view showing asymmetrical pseudoseptum (arrow) F internal and external aspects of valve in the narrow part G valvocopula lying inside narrow part of valve H, I portion of frustules in girdle view, showing multiple rows of pores on mantle, valvocopula with apical notch (arrow), and copula with pores continuing around the pole (arrowhead) J detail of copula, for comparison with Fig. 22J K pole of valvocopula showing arched slits L frustule in girdle view showing pleura M fragment of the pleura, showing fimbriae. Scale bars: 50 µm (A, B); 10 µm (C); 5 µm (D–I, K); 2 µm (J, K, M).