Ulnaria pandurata-uniseriata sp. nov., external view, SEM A, B two complete valves, note panduriform valve outline C, D two middle part details from A, B, respectively, note rectangular central areas E, F two apical details from B, note two horn-like projections protruding over ocellulimbus. Scale bars: 10 μm (A, B); 1 μm (C, D); 2 μm (E, F).