FIGURES 25–32. 25, 26. Achnanthes citronella. Individuals from type slide 43609, labelled as 'Jolo Jolo, Sulu, Philippine Islands, 3-17' (see Fig. 34), A. Mann's collection, housed in US. Lemon-shaped SV with an elliptic SV sternum (Fig. 25, arrowhead) and rectangular areolae without axial arrangement, RV finely striated, detached open valvocopula without fimbriae (Fig. 26, arrow) and a short butterflyshaped stauros. 27–32. Achnanthes trachyderma. 27–29. Individuals from Meister's slides collection, housed in Z. Frustule from slide 3409001 showing a large RV stauros and fine RV striae (Fig. 27), and SV coarse striation (Fig. 28). 29. Illustration of the lectotype. A RV from slide 309008, with a fine striation and a narrow extended stauros. 30–32. Achnanthes trachyderma. Individuals from Society Archipelago, South Pacific, with relatively large stauros (Fig. 30, arrowheads), SV striae parallel, only slightly radiate at the apices, narrow sternum (Fig. 31). 32. RV with fine striae and large and thin stauros. Scale bars = 10 μm.