FIGURES 45–51. Achnanthes trachyderma. Individuals from Society Archipelago, SEM. 45 in Achnanthes citronella, A. trachyderma comb. nov. (Bacillariophyta) and allied taxa pertaining to the same morphological group

FIGURES 45–51. Achnanthes trachyderma. Individuals from Society Archipelago, SEM. 45. SV external side, with narrow sternum. 46. Apices with areolae (arrowhead). 47. Valvocopulae system lacking fimbriae (arrowhead). 48. SV internal side, with open SVVC (arrow) and no fimbriae (arrowheads). 50. Internal SV areolae pattern and no areolae on apices. 49. Detail of the cingulum composed of the two valvocopulae (SVVC and RVVC) and a supplementary copula (C). 51. Detail of the internal structure of the SV areolae. Scale bars = 5 μm (Figs 45–48, 50); 1 μm (Figs 49, 51).