Ulnaria blancoi sp. nov., external view, SEM A, C two complete valves, note central area present or absent B middle part from A, note central area completely absent D middle part from C, note small central area flanked by marginal short striae E, F two apical details, note two horn-like projections protruding over the ocellulimbus (E, two arrows). Scale bars: 20 μm (A, C); 2 μm (B, D, F); 1 μm (E).