FIGURES 21–27 in Bicudoa amazonica gen. nov. et sp. nov. (Bacillariophyta)-a new freshwater diatom from the Amazon basin with a complete raphe loss in the Eunotioid lineage

FIGURES 21–27. SEM micrographs of Bicudoa amazonica in external view. Fig. 21 Whole frustule in valvar view showing irregular silica deposition along the central part of the valve; central valve face with somewhat concentrated silica deposition at the apical axis; Fig. 22 Valve face apex detail showing the complete absence of raphe aperture system; small foramina forming the striae; Figs 23–24 Detail of both extremities showing reduced slightly radiate striae; note the absence of apical pore fields and external raphe openings on the mantle; axial area narrow, more or less eccentric; Fig. 25 Apex detail with small wart-like silicate on the valve edges (arrow); Fig. 26 Detail of apical valve outline in oblique view; Fig. 27 Detail of one valve and the cingulum in girdle view showing perforated Eunotia-like open copulae (white arrows) with multiporoid striae. Note the numerous open connective bands. Scale bars: Fig. 21: 10 µm; Figs 22–25: 2 µm; Figs 26–27: 5 µm.