Moreneis is a genus of benthic, pennate diatom described from samples collected in Korean sand flats. Its distinguishing features are the shape of the plastid and the raphe. Analysis of published data suggests that this genus has been observed in tropical, marine waters, especially in the Pacific.
From Jinsoon Park et al. 2012
Cells are solitary. Single large plastid appressed to the girdle of secondary side, with two transapically extended lobes, which are often irregularly bifurcate. To date, four species are known from the type habitat, all being marine. Frustules naviculoid in terms of symmetry and raphe system. Frustules in girdle view rectangular, girdle composed of a few narrow, regularly perforated bands. Perforations composed of relatively robust areolae, seemingly in two rows. Valve face flat, turning gradually toward the shallow mantle. Valves elliptic to linear-elliptic with protracted rostrate ends. Valve face flat or slightly domed, and slightly twisted along the apical axis. Axial area narrowly linear, widening toward the central area. Raphe straight in the middle of the valve, moderately to severely eccentric near the apices. Voigt faults distinct, often marked by the occurrence of a solitary areola. External central raphe endings expanded and grooved, bent in opposite directions to one another. Often a small dent-like depression is present at the opposite side of each of the external central raphe endings, which is observed as a somewhat vague point-like structure under LM. External terminal raphe fissures strongly hooked with deeply grooved endings, bent to the same side of the central raphe endings. Internal central raphe endings hooked in opposite directions, or, straight and simple. Internal terminal raphe endings simple with helictoglossa. Striae uniseriate, composed of large round or transapically elongated areolae occluded by simple volae. Areolae located along the raphe-sternum rather more conspicuous than the remaining ones.