Toxarium undulatum from Grunow’s Honduras material A, B entire valve, 700 µm long, and detail of central portion, showing long-wavelength undulations C portion with the central inflation, showing mantle depth, internal costae, valvocopula and copula (stria density 14 in 10 µm) D frustule in girdle view, showing vertical wave in rows of areolae with inserted arcs (arrows); notice also the different depths of the two mantles (stria density 17 in 10 µm) E portion of valve with copula and valvocopula F, G valvocopula pole, abvalvar and advalvar surfaces, respectively, showing series of arched slits (compare with Fig. 22F) H pole of frustule showing fimbriate pleura and notch in valvocopula. Scale bars: 100 µm (A); 25 µm (B); 10 µm (C–E); 5 µm (F–H).