Ulnaria jishou-biseriata sp. nov., external view, SEM A a frustule in valve view B middle detail from A, showing central area flanked by a few marginal striae only on one side C, D two apical details from A, note a few serrated projections protruding over the ocellulimbus (C, three arrows) E a middle part showing the central area flanked by shortened striae on both sides F a middle part showing a rectangular central area. Scale bars: 20 μm (A); 2 μm (B, E, F); 1 μm (C, D).