The tusk shells or tooth shells, often referred to by the more-technical term scaphopods /ˈskæfəˌpɒd/ (Greek, "boat-footed"), are members of a class of shelled marine mollusc with worldwide distribution, and are the only class of exclusively infaunal marine molluscs. Shells of species within this class range from about 0.5 to 15 cm in length. Members of the order Dentaliida tend to be significantly larger than those of the order Gadilida.