FIGURES 15–18. Stephanodiscus neoaegypticus v. fekrii, SEM. Fig. 15. External valve with a convex central area. Fig. 16 in Stephanodiscus Ehr. species from Holocene sediments in the Faiyum Depression (Middle Egypt)

FIGURES 15–18. Stephanodiscus neoaegypticus v. fekrii, SEM. Fig. 15. External valve with a convex central area. Fig. 16. Internal valve showing two rimoportulae (arrowed). Fig. 17. Detail of internal marginal zone showing fultoportulae with either three or four satellite pores. Fig. 18. Internal central area fultoportula with two satellite pores. Scale bars = 2 µm (Fig. 15), 5 µm (Fig. 16), and 1 µm (Figs 17, 18).