shells - front view

absent adult almost aplacophores atypical bivalves bone cases caudofovacopy ates cephalopods certain character chitons class classes conchyliology consonants covered cuttlefishes daylight dedicated dental even external formerly gastropods grouped groups included majority malacology mollusk mollusks monoplacophores most number opisthobranches other outside oysters pieuvres polyplacophores rather reason reduced scaphopodes secrete shell shooting skeleton slugs small snails solacopy nogastres sometimes squids study subdivision systematically undefined well without