FIGURES 16–18 in Gyrosigma xiamenense sp. nov. (Bacillariophyta) from the middle intertidal zone, Xiamen Bay, southern China

FIGURES 16–18. Gyrosigma xiamenense sp. nov., external views, SEM. 16. A whole valve, note that the raphe sternum has single curvature only. 17. Apex showing an isolated crescent of apical pores (three black arrowheads), terminal raphe fissure, round pores located on the mantle (three black arrows) and on the other side continuing up to the longitudinal middle line of the valve (three white arrows), and elongated narrow slits. 18. Central area, showing proximal raphe fissures turning first in opposite directions, then both final parts of the fissures run nearly parallel to the longitudinal striae. Peripheral stria condensation (three double-headed arrows), and round pores located on the mantle (three arrows). Scale bars = 20 μm (Fig. 16), 1 μm (Figs 17–18).