Climacosphenia elegantissima sp. nov., cont. GU52AI-1, except GU52U-2 (B) and GU52X-1 (G, H) A whole mount of colony in SEM, showing contrasting width versus depth of frustule in the stem (arrows at approximately same distance from apical poles) B portion of holotype in LM; although specimen is broken in two places, the basal pole of the valvocopula is also present, total length ca. 835 µm C apical pole of valve and valvocopula in LM, showing parallel sides of annulus and some misaligned unions in the craticular bars D SEM of external valve surface at apical pole, showing annulus (double-headed arrow) continuing around apical pole, two spines, and crescent of scattered areolae at top of mantle (arrow) E external valve surface at basal pole, showing variation in areola density and alignment within the annulus, apparent discontinuity of annulus at pole, and width of basal pole relative to stem (cf. H at same scale) F internal aspect of basal pole of valve and valvocopula, showing absence of pseudoseptum (arrow) and associated structure in valvocopula G, H internal aspect of valve at apical pole, showing crescent of scattered areolae (arrow) and in the narrow stem, respectively I oblique view of basal pole with valve and valvocopula, showing increase in areola density on the valvocopula around the pole (arrow) and short row of pores on pars interior (arrowhead). Scale bars: 200 µm (A); 50 µm (B); 10 µm (C–H); 5 µm (I).