FIGURES 10–15 in Surirella subrotunda sp. nov. and Surirella parahelvetica sp. nov., two new diatom (Bacillariophyta) species from Lake Prespa, Macedonia

FIGURES 10–15: Surirella subrotunda (SEM). Figs 10, 12, 14. External views. Figs 12, 14. Illustrating raphe formation on keel, 4–5 fenestral bars, uniseriate areolae pattern and small abundant papillae on valve face. Figs 11, 13, 15. Internal valve views. Fig. 11. Illustrating asymmetrical depression (white arrow) and marginal opening into alar canals. Fig. 13. Illustrating terminal raphe fissure and internal opening of areolae. Fig. 15. Illustrating internal valve face and external view of alar canals with multiseriate striae extending to keel. Raphe fissures on the keel terminate as simple pores, not deflected. Scale bars in Fig. 11 = 20 µm; Fig. 10 = 10 µm; Figs 12, 13, 15 = 5 µm; Fig. 14 = 2 µm.