A–F Navicula sparsilineolata Chudaev, Glushchenko, Kulikovskiy & Kociolek, sp. nov. SEM. Sample no 00962. A–C external views D–F internal views A–C external views D–F internal views A, D the whole valve B, E central area C, F valve end A black arrow shows the very slightly elevated raphe-sternum B white arrows show the drop-like central pores. Black arrows show the larger triangular insertion in distal part. White arrowheads show the small projections in proximal part. Black arrowhead shows the transapical sutures C black arrow shows the terminal raphe fissure. White arrows show the longitudinal grooves where areola openings are located. Black arrowhead shows the transapical sutures. White arrowheads show the small isolated apical areolae D black arrowheads show the helictoglossae E black arrow shows the stria which slightly wider than virgae. White arrows show the areola openings occluded with hymenes. Black arrowheads show the central raphe endings. White arrowheads show the raphe slits F black arrow show the stria which are wider than virgae. Black arrowhead shows the helictoglossa. White arrowhead shows the raphe slit. Scale bars: 10 μm (A, D); 1 μm (B, C, E, F).