FIGURES 13–22. Scanning electron micrographs. Petroplacus lizae from type material. 13−16. SEM external views of entire valve showing raphe and striae structure. 14. SEM external detail of valve centre with proximal raphe endings expanded into T-shaped grooves, uniseriate striae. 15, 16. SEM external detail of valve apex with terminal fissures. 19–22. SEM views of entire valve showing raphe and striae structure. 20. SEM internal detail of valve centre with proximal raphe endings, volate occlusions of the areolae. 21. SEM internal detail of valve apex with helictoglossa, round pores occluded by volae. 22. SEM internal detail of broken valve showing the pores apertures. 17. SEM detail of girdle band with a single row of pores. 18. SEM detail of two girdle bands. Scale bars = 10 μm (Figs 13, 19), 3 μm (Figs 14, 20, 21), 5 μm (Figs 17–18), 2 μm (Fig.22), 1 μm (Figs 15–16).