A new saline species of the diatom genus Entomoneis is described using light and electron microscopic observations. The species, E. reimeri sp. nov., is distinguished from other Entomoneis species by a distinctive striae count, a lack of junction-dots and the micromorphometric structures of the valve face. Most members of this genus are considered marine or brackish water forms. The type locality of this taxon is a natural salt marsh in Russell County, Kansas.