Source : Webster's Revised Unabridged Dictionary (1913)

Lithodomus \Li*thod"o*mus\, n. [NL. See {Lithodome}.] (Zo["o]l.)
   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}.

   Note: 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.