FIGURES 1–17 in Lectotypification, emended description and distribution of Planothidium distinctum (Achnanthidiaceae, Bacillariophyceae)

FIGURES 1–17: Original drawings of Planothidium distinctum and Achnanthes hirta, LM and SEM images from specimens in Messikommer's sample. Fig 5, designated here as lectotype (BP 2210). Figs 1, 2. Reproduction of Messikommer's drawings (1954: 32, pl. 1, figs 2a, 2b). Figs 3, 4. Reproduction of Carter's drawings of Achnanthes hirta (Carter 1970: 609, pl. 1, figs 10, 11). Figs 5, 7–9. Raphe valves in LM. Figs 6, 10. Rapheless valve of Planothidium distinctum in LM. Scale bar = 10 µm. Figs 5 and 6 are of the same specimen each at a different focus. Fig. 11. External view of raphid valve, note the hardly expanded proximal raphe endings. Fig. 12. External view of rapheless valve, note three rows of areolae becoming biseriate towards axial area. Fig. 13. Internal view of rapheless valve. Fig. 14. Whole frustule, external view of rapheless valve. Fig. 15. Internal view of raphid valve. Fig. 16. Details of internal view of valve with poroids on internal edge of mantle; number is exactly 3 x number of striae. Fig. 17. Internal view of rapheless valve with poroids. Note slightly curved valve end. Scale bars = 5 µm for figs 11– 15, 2 µm for figs 16, 17.