FIGURES 15–18 in The diatom genus Longinata Hajós (Bacillariophyta): structure, relationships and distribution

FIGURES 15–18: Longinata acuta SEM, Fig. 15, pair of whole valves; Fig. 16, detail from specimen in Fig. 15, showing rimoportula (arrow) and sparse poroids; Fig. 17, detail showing rimoportula (arrow) and 'pegs' (double-headed arrow). Scale bars = 20μm (Fig. 15), 5μm (Fig. 16, 18), 2μm (Fig. 17).