FIGURES 6–9 in Entogoniopsis gen. nov. and Trilamina gen. nov. (Bacillariophyta): a survey of multipolar pseudocellate diatoms with internal costae, including comments on the genus Sheshukovia Gleser

FIGURES 6–9. An overview of valve morphology in Sheshukovia Gleser and Medlinia Sims. Figs 6–7: Sheshukovia kolbei (Hustedt) Gleser. Fig. 6: Oblique external view showing flat polar pseudocelli, shallow transverse folds across the projections, and an inconspicuous external tube of a rimoportula (arrow). Fig. 7: Oblique internal view. Note the openings of the rimoportulae (arrows), and the smooth hyaline margin of the mantle (arrowhead). Fig. 8: Medlinia weissei (Grunow) Sims, external valve view, showing deep transverse folds separating the projections from the central area, and prominent external tubes of the rimoportulae (arrow). Fig. 9: Medlinia venusta (Witt) Sims, oblique internal view, showing internal costae associated with the transverse folds, internal openings of the rimoportulae (arrow), as well as serrations along the mantle margin (arrowhead).