Frustules biraphid, asymmetrical to the apical axis with convex dorsal margin and usually concave ventral margin, symmetrical to the transapical axis. Raphe biarcuate from the dorsal margin to the center of the valve, raphe canal visible at the apices of the valve face only, or at the central nodule and apices. Raphe canal opens to the valve interior by elliptical holes (called portules) that occur internally to the fibulae. Robust transapical costae present, Valvocopulae possess inwardly-projecting structures that clasp around the costa. Differentiated from Rhopalodia primarily in the structure of the raphe system.
Each image is accompanied by the genus and species, California Academy of Sciences slide number (ie. CAS 612010), location of the specimen on the slide, and dimension in microns.