Solitary cells or joined in ribbon-like colonies ribbon-like. In girdle view, the frustule can be rectangular or square, while in valve view it appears triangular or more rarely biangular or quadrangular. Each valve has numerous crests in the marginal area, small swellings in each corner and, in the central area, a labiate process that on the outside is similar to a long tube. The valve surface is decorated with pores of various dimensions and uniseriate rows of areolae that irradiate from the centre of the valve. Distributed throughout the cytoplasm are numerous small discoid chloroplasts.

The genus is planktonic although some species can be benthic; typical of warm waters.