Echinocardium cordatum

TheSea Potato, Echinocardium cordatum, dug up by a bait digger
immediately tried to bury into the substrate.  It uses the spines on the
ventral surface to move the sand away from underneath it.  As it buries
itself in the substrate it pushes up a ridge of silt and sand up in
front of it.  It can bury itself remarkably quickly for such a slow
moving animal.