Cells isovalvar, isopolar and bilaterally symmetrical.
Frustules linear-elliptic, elliptic-rhombic, elliptic or rhombic with rounded, rostrate or slightly apiculate poles; cells in girdle view rectangular.
Cells can be joined at the valve face and form ribbon-like colonies.
Striae uniseriate with small, round areolae, striae parallel and sometimes slightly radiate towards poles.
Internally prominent transapical ribs extend from the sternum to the mantle.
Sternum narrow to wide and diffuse.
Complex girdle composed of several copulae and a distinct pleural band.
One to several rimoportulae in different locations on the valve face.
Apical pore fields present at both poles.
Non–functional spines form one or several rows along the valve margin. They can sometimes be very few in numbers or missing.
Several elliptical or irregularly lobed chloroplasts.