When a lingulide is on a sandy substrate,
fluctuations in pressure within the coelomic
body and pedicle cavities open and close the
valve. When the lingulid starts to burrow
(Fig. 409), the pedicle stiffens with its distal
bulb pressing downward to prop up the
valves, thereby bringing the anterior margins
of the valves into contact with the sediment.
Penetration takes place by means of a combination
of scissor like movements of the
valves and ejection of water from them that
loosen the sand prior to a downward movement
of the shell and an upward transportation
of mucous-bound sand by the lateral
setae of the mantle