lithodomus

‖n. [ NL. See Lithodome. ] (Zool.) A genus of elongated bivalve shells, allied to the mussels, and remarkable for their ability to bore holes for shelter, in solid limestone, shells, etc. Called also Lithophagus. [ 1913 Webster ]

☞ These holes are at first very small and shallow, but are enlarged with the growth of the shell, sometimes becoming two or three inches deep and nearly an inch diameter. [ 1913 Webster ]