Abstract
The taxonomie status of the species Amphora eulensteinii Grunow is at present insufficiently known. The study of morphology and fine structure of this species, discovered in core samples from Rhode Island, revealed that it is characterized by the presence of lineolate, slitlike areolae, a dorsally widened axial area and a ventrally displaced raphe that runs internally on a dorsally bended silica rib. All of these structures together with the shape of the valve clearly place this species in the genus Seminavis as it was established by Mann (in Round et al. 1990). The lack of verified original material has led to the designation of a neotype for Seminavis eulensteinii (Grunow) Danielidis, Ford & Kennett comb. nov.