The cells have a lentil-shaped appearance with a strongly curved valve face. They have a circular cross-section and lack a prominent cingulum (a raised band or ridge). The valve area is divided into distinct radial sectors, and these sectors have clear areolation (cellular patterning) as opposed to a less-defined central area. Before cell division, a pair of cells appears elongated and cylindrical due to the presence of numerous visible girdle bands. The chloroplasts within these cells are small, rounded, and highly pigmented. They are arranged in a star-shaped pattern..