No radula or odontophore. Shells are attached dorsally and open ventrally. Appropriate muscles of the foot contract and the foot extends into the substrate.
Blood is forced into the foot so that the tip of the foot dilates and forms a pedal anchor.
Adductors contract, the shell closes and the water forced out loosens the substrate around the shell so it no longer is an anchor. The pedal anchor persists. Pedal retractor muscles contract, pulling the animal down toward the foot. A rocking motion helps the shell move down through the sediment. If you've ever tried to catch one of those, you understand.