Dorsal margin convex, ventral margin convex to more or less straight, frustules narrowly rectangular in girdle view.
Valves more or less bilaterally symmetrical to dorsiventral, usually with protracted rostrate to capitate apices.
Striae uniseriate, external areolae openings round or transapically elongate, internally in deep depressions between the virgae.
Raphe usually more or less central, externally proximal raphe endings deflected slightly to the dorsal side, distal raphe endings deflected towards the ventral side, internally the central raphe endings hidden, intermissio not visible.
No apical pore fields or isolated pores.
Girdle bands with single row of pores.