FIGURES 17–23. Diploneis zannii, SEM. 17–19 in Revision of the type material of Diploneis zannii Frenguelli (Bacillariophyceae)

FIGURES 17–23. Diploneis zannii, SEM. 17–19: External valve view. 17. Whole valve.18. Detail showing central area and proximal raphe ends. 19. Detail showing valve end and distal end of raphe. 20–23. Internal valve view 20. Whole valve. 21. Detail showing valve end; note distal end of raphe, helictoglossa and round areolae of the striae (arrowheads). 22. Detail showing central area. 23. Detail of broken valve, note the fungiform section of transapical ribs (arrows) and the rounded areolae (arrowheads). Scale bars: Figs 17, 20: 10 μm; Figs 18–19, 21–23: 2 μm.