Ulnaria neobiceps sp. nov., internal view, SEM A a complete valve B middle part detail from A, note the very small central area (arrow) C, E two poles from A, note that valve margins do not constrict near the capitate apices (two arrows, respectively) D, F two apical details, note the capitate apices and apical pore field. Scale bars: 20 μm (A); 2 μm (B–F).