Ammonites are an extinct group of marine invertebrate animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs are more closely related to living coleoids than they are to shelled nautiloids such as the living Nautilus species.
Sally sells sea shells by the sea shore. She sells sea shells on the sea shore; The shells that she sells are sea shells I'm sure. So if she sells sea shells on the sea shore, I'm sure that the shells are sea shore shells.