Hannaea inaequidentata, half mother frustule, external view, SEM 103 half mother frustule, note its rounded outline 104 middle detail of Fig. 103 showing longitudinal perizonium (arrows) and plaques (arrowheads) 105 apex detail of Fig. 103 106 apex detail of Fig. 103 showing four girdle bands and hypovalve with spines (arrows). Scale bars: 10 μm (103), 2 μm (104–106).