FIGURES 17–20 in Gyrosigma rostratum sp. nov. (Bacillariophyta) from the low intertidal zone, Xiamen Bay, southern China

FIGURES 17–20. Gyrosigma rostratum, sp. nov., internal views, SEM. 17–18. Two types of valve. 19. Detail of Fig. 17, showing helictoglossa, axial costa (arrow) more markedly developed on one side of raphe and apical pores (black arrow). 20. A detail of Fig. 17, showing central bars (arrows) and T-shaped proximal raphe endings. Scale bars = 10 μm (in Figs. 17–18), 1 μm (in Figs. 19–20).