Gomphonema truncatum

Valves are clavate, with a tumid center. A constriction at the headpole and broad apex creates a distinctly capitate headpole. The footpole is narrow and rounded. The axial area is straight and expanded on either side of the axial area to form a “bow-tie” shaped central area. A single, rounded external stigma opening is present in the central area. The raphe is lateral and undulate, with expanded external proximal ends. Striae are radiate, indistinctly punctate, and become parallel toward the headpole. Striae are strongly radiate at the footpole. A distinct apical pore field is present at the footpole. Septa and pseudosepta are present at the poles.