sigmoid

Valve lanceolate, sigmoid; axial area very narrow, central area small; stri punctate, in transverse and oblique lines.

Valve linear-lanceolate with produced rostrate apices, asymmetrical, sigmoid; pseudoraphe narrow; pseudo-nodule large.

Valve lanceolate, sigmoid; axial area very narrow, central area small; stri punctate, in transverse and longitudinal rows.

The raphe confined within a sigmoid keel or extension of the valve; the central and terminal nodules indistinct.

Valve linear, slightly sigmoid, tapering to the sub-capitate ends; keel puncta, 11 in 10 ; stri subtle.