Navicula goersii

Frustules are flat, almost always coming to rest in valve view due to shallow mantles (1.5-2.0 µm deep). Valves are broadly lanceolate with acutely rounded ends in all but the smallest specimens. The axial area is narrow. Central area is broad, rectangular and reaches nearly to the valve margins. A single, shortened stria is present on each side. External raphe fissures are straight and threadlike. Proximal raphe ends are slightly inflated and relatively distant from one another. Terminal raphe fissures are bent diagonally toward the valve margin and are characteristically in close contact with a single areola at each apex, making the raphe fissures appear as hook-like terminations. Striae are broad, lineate, radiate and slightly curved about the central area. The striae extend onto the valve mantle. A crown of small areolae of different shapes are present at each valve apex. Striae are parallel or slightly convergent toward the valve apices.