<Ul> <Li> Aperture : the opening of the shell </Li> <Li> Lip = peristome : the margin of the aperture </Li> <Li> Apex : the smallest few whorls of the shell </Li> <Li> Body whorl ( or last whorl ) : the largest whorl in which the main part of the visceral mass of the mollusk is found </Li> <Li> Columella : the `` little column '' at the axis of revolution of the shell </Li> <Li> Operculum : the `` trapdoor '' of the shell </Li> <Li> Parietal callus : a ridge on the inner lip of the aperture in certain gastropods </Li> <Li> Periostracum : a thin layer of organic `` skin '' which forms the outer layer of the shell of many species </Li> <Li> Peristome : the part of the shell that is right around the aperture , also known as the lip </Li> <Li> Plait : folds on the columella . </Li> <Li> Protoconch : the nuclear or embryonic whorl ; the larval shell , often remains in position even on an adult shell </Li> <Li> Sculpture : ornamentation on the outer surface of a shell <Ul> <Li> Lira : raised lines or ridges on the surface of the shell </Li> </Ul> </Li> <Li> Siphonal canal : an extension of the aperture in certain gastropods </Li> <Li> Spire : the part of the shell above the body whorl . </Li> <Li> Suture : The junction between whorls of most gastropods </Li> <Li> Teleoconch : the entire shell without the protoconch ; the postnuclear whorls . </Li> <Li> Umbilicus : in shells where the whorls move apart as they grow , on the underside of the shell there is a deep depression reaching up towards the spire ; this is the umbilicus </Li> <Li> Varix : on some mollusk shells , spaced raised and thickened vertical ribs mark the end of a period of rapid growth ; these are varices </Li> <Li> Whorl : each one of the complete rotations of the shell spiral </Li> </Ul>
<Ul> <Li> Aperture : the opening of the shell </Li> <Li> Lip = peristome : the margin of the aperture </Li> <Li> Apex : the smallest few whorls of the shell </Li> <Li> Body whorl ( or last whorl ) : the largest whorl in which the main part of the visceral mass of the mollusk is found </Li> <Li> Columella : the `` little column '' at the axis of revolution of the shell </Li> <Li> Operculum : the `` trapdoor '' of the shell </Li> <Li> Parietal callus : a ridge on the inner lip of the aperture in certain gastropods </Li> <Li> Periostracum : a thin layer of organic `` skin '' which forms the outer layer of the shell of many species </Li> <Li> Peristome : the part of the shell that is right around the aperture , also known as the lip </Li> <Li> Plait : folds on the columella . </Li> <Li> Protoconch : the nuclear or embryonic whorl ; the larval shell , often remains in position even on an adult shell </Li> <Li> Sculpture : ornamentation on the outer surface of a shell <Ul> <Li> Lira : raised lines or ridges on the surface of the shell </Li> </Ul> </Li> <Li> Siphonal canal : an extension of the aperture in certain gastropods </Li> <Li> Spire : the part of the shell above the body whorl . </Li> <Li> Suture : The junction between whorls of most gastropods </Li> <Li> Teleoconch : the entire shell without the protoconch ; the postnuclear whorls . </Li> <Li> Umbilicus : in shells where the whorls move apart as they grow , on the underside of the shell there is a deep depression reaching up towards the spire ; this is the umbilicus </Li> <Li> Varix : on some mollusk shells , spaced raised and thickened vertical ribs mark the end of a period of rapid growth ; these are varices </Li> <Li> Whorl : each one of the complete rotations of the shell spiral </Li> </Ul>
the opening to the snail shell is known as the
the opening to the snail shell is known as the
Aperture
Aperture