Ardissoneopsis gracilis sp. nov. (GU44BJ-4, except B TK28) A–C three specimens to scale in LM to show size range: valves from Guam (A) and Chuuk (B), frustule from Guam in girdle view (C) showing heteropolarity D frustule in SEM tilted 60°, showing both valve and girdle faces E, F pole and mid-section of holotype G–K external views of valve in SEM with other species adjacent for comparison (GU44BJ-4): index image (G) with locations of details marked, apical pole (H) (shown by depth of mantle), compare stria density with Ardissoneopsis appressata (A. g.); top half of center (I), offset areolae in striae within the oval suggest location of annulus; narrow portion below center (J), compare with scattered areolae in adjacent Toxarium undulatum (T. u.); basal pole (K), note spines on both poles L, M internal aspect near middle and at the apical pole, showing lack of costae N, O girdle view of frustule apical and basal poles, showing taper in mantle and girdle bands P possible piece of pleura (pl?) with fimbriae Q, R fimbriate edges of valvocopula and copula, respectively. Scale bars: 50 µm (A–D, G); 10 µm (E, F, H–K); 5 µm (L–R).