cuneate

At the time of metamorphosis, young are dark brown with specks of black and with a dark, cuneate, leaflike middorsal mark.

Cuneate (Fig. 91, c): Rods swollen slightly at one pole and more or less pointed at the other; wedge-shaped.

Valve symmetrical in zone and valve view along the sagittal line, but asymmetrical to the transverse axis, cuneate.

Frustules in zone view cuneate, adnate in circular or spiral fasci, at length becoming free.

Valve symmetrical with respect to the longitudinal axis, more or less cuneate; cost and stri transverse.