The paper presents the description of Seminavis atlantica Garcia, a psammic marine diatom from dissipative sandy beaches from southern Brazil. It is characterized by its convex linear dorsal margin (37 to 50% of its length is in a straight line), linear ventral margin and raphe located very close to the ventral margin. Its morphology is compared to similar species such as Amphora clevei Grunow, Amphora angusta (Greg.) Cleve var. orientalis Allem, Amphora ventricosa Gregory and Amphora eulesteinii Grunow.
benthic diatoms; Brazil; marine sandy beaches; new taxa; taxonomy
