Cells linear, linear-lanceolate or elliptical, often with rostrate or subcapitate apices, more often lying in valve view.
Isovalvar, isopolar, bilaterally symmetrical.
Striae uniseriate, dense (often difficult to resolve in LM), clearly radiate and abruptly convergent towards the valve ends, striae extending onto the mantle. Areolae very small, round, occluded by fine pore plates (hymenes) at their external apertures.
Axial area narrow, width of central area variable but not extending to the valve margins.
Raphe almost straight or curving slightly towards one side (the primary side) at the centre, external central raphe endings not or slightly expanded, internal central endings bent towards the same (primary) side, terminal fissures deflected to one side (in the opposite direction to the central endings, i.e. towards the secondary side).