FIG. 15 in Small naviculoid species of Kobayasiella Lange-Bertalot, Adlafia Moser, Lange-Bertalot & Metzeltin, Nupela Vyverman & Compère and Sellaphora Mereschowsky from Tursujuq National Park, Hudson Bay region, Nunavik, Québec

FIG. 15. — SEM images of Nupela tenuicephala (Hustedt) Lange-Bertalot: A, B, external views of complete valves with recessed depressions covered with multiporoid volae; C, internal view of the whole valve; D, external view of the central area showing the expanded proximal raphe fissures and multiseriate poroid covers over the areolae; E, internal view of the central area with bent proximal fissures; F, internal views of the apex, helictoglossa small and elevated. Areolae interrupted around the apex. Scale bars: A-C, 5 µm; D, 2 µm; E, F, 1 µm.