These genera have a raphe on both valves and are symmetrical to both the longitudinal and transverse axis of the valve. This is a very large and diverse group. These genera have a raphe on both valves which is borne on a specialized tube-like structure called a canal. The canal raphe is usually displaced from the midline of the valve. In these genera, the raphe is wrapped around the margin of each valve and raised in a special structure called a wing.
Cells are usually relatively large.