FIGURES 15–20 in Ultrastructure of four Surirella taxa (Bacillariophyceae) from Qinghai Province, northwest China, with reference to the characteristics of portulae

FIGURES 15–20. Surirella liubingii sp. nov., SEM, external view. 15–17. Three valves showing the valve shape, the pattern of costa-stria bundles (CSBs, white arrows labeled in Fig. 16) alternated with over-fibula costae (OFCs, black arrows labeled in Fig. 16) from pole to pole. 18. Middle section of the valve, detail from Fig. 17, note CSBs, OFCs, and multiseriate striae. 19, 20. Details of the valve apices from Fig. 17, note the simple, interrupted raphe endings at both the footpole (Fig. 19, two arrows) and headpole (Fig. 20, two arrows). Scale bars = 5 μm (Figs 15–17), 1 μm (Figs 18–20).