FIGURES 52–57. Achnanthes trachyderma. Individuals from Society Archipelago, SEM. 52 in Achnanthes citronella, A. trachyderma comb. nov. (Bacillariophyta) and allied taxa pertaining to the same morphological group

FIGURES 52–57. Achnanthes trachyderma. Individuals from Society Archipelago, SEM. 52. RV external side with laciniate stauros reaching almost the margin. 53. RV internal side with the stauros marginally delineated by very short striae (arrow), low helictoglossa (arrowhead). 54. RV external side with large stauros (arrowheads). 55. Detail of the central area in internal side, with areola domed hymenes (arrowhead). 56. RV apex with strongly bent striae with a marginal row of larger areolae. 57. Terminal raphe fissure continuing on the mantle. Scale bars = 5 μm (Figs 52–54); 1 μm (Figs 55–57).