Sellaphora laevissima

Valves are linear with slightly bowed margins. Apices are broadly rounded with small polar bars visible. Raphe branches are filiform, with a broad curve halfway between the center and end of the valve. Proximal raphe ends are inflated and unilaterally bent to the primary valve side. Terminal raphe fissures are initially deflected in a small question mark shape to the primary side, but then sharply curve to the secondary side on the mantle. The conopeum is small and located within a narrow, linear axial area that becomes expanded near the central area. The conopeum appears as narrow grooves running alongside the raphe and visible as faint lines under LM. The central area is laterally expanded and rectangular to weakly bow-tie shaped. The central area is bordered by 3-4 shortened stria of similar lengths. Striae are slightly curved and reflexed and are parallel at the valve center becoming slightly radiate at the apices. Areolae very fine, and not discernible in LM.

Sellaphora laevissima is part of a species group, or complex, that has not be adequately characterized (Mann et al. 2008).

The type material of Navicula laevissima contains many species of Sellaphora and it is uncertain as to which specimen corresponds to the holotype (Mann 1989). A lectotype was designated from Kützing material housed at the British Museum (Schoeman and Archibald 1976-1980, Lange-Bertalot et al. 2003).