Ulnaria pandurata-biseriata sp. nov., internal view, SEM A a valve with a valvocopula B middle detail from A, note the unornamented middle portion of valvocopula (arrow) C, D apical details from A, note serrated projections over each virga (arrows) and valvocopula without ornamentation at each apex. Scale bars: 10 μm (A); 2 μm (B–D).