FIGURES 18–25. Surirella tayronarum spec. nov. SEM. 18–23 in Surirella tayronarum spec. nov. (Surirellaceae, Bacillariophyta) from Colombia

FIGURES 18–25. Surirella tayronarum spec. nov. SEM. 18–23. Valves in external view. 18. View of the whole valve, note the elevated median ridge and the sunken end. 19. Detail of the valve end showing median ridge, fenestrae and tendrils. 20. Valve end showing median ridge, raphe canal and granules. 21. Detail of the wing, showing the fenestrae and tendrils. 22. Detail of the valve face. Note smooth raphe canal, fenestrae, tendrils and granules. 23. Detail of the granules. 24. Detail of the mantle, note the line of slits and silica plaques. 25. Valve in girdle view, detail of the pole showing the expanded raphe end. Scale bars: Fig. 18: 20 μm, Figs 19–20: 10 μm, Figs 21–22, 24–25: 2 μm, Fig. 23: 1 μm.