FIGURES 16–20 in An unusual freshwater diatom with bilobate ends from the Mid-Miocene of East Antarctica: Staurosirella tigris sp. nov. (Fragilariaceae, Bacillariophyta)

FIGURES 16–20. Staurosirella tigris sp. nov., SEM pictures taken from the holotype population (sample WD 19, BR-4689). 16. External view of an entire valve. 17. External detail of the valve margin showing the conical spines with hollow bases and the linear areolae. 18. External detail of the apical pore fields. 19. Internal detail showing part of the valvocopula and the copulae. 20. Internal detail of a valve apex showing the apical pore fields and some vimines with small or remnant volae. Scale bars = 10 µm (Figs 16, 19), 5 µm (Figs 18, 20), 1 µm (Fig. 17).