See text Scientific classification or biological classification is a method by which biologists group and categorize species of organisms. ... “Animalia” redirects here. ... Classes Caudofoveata Aplacophora Polyplacophora Monoplacophora Bivalvia Scaphopoda Gastropoda Cephalopoda † Rostroconchia † Helcionelloida † ?Bellerophontidae The molluscs (British spelling) or mollusks (American spelling) are members of the large and diverse phylum Mollusca, which includes a variety of familiar animals well-known for their decorative shells or as seafood. ... Subclasses Eogastropoda (True Limpets and relatives) Orthogastropoda The gastropods, gasteropods, or univalves, are the largest and most successful class of mollusks, with 60,000-75,000 known living species comprising the snails and slugs as well as a vast number of marine and freshwater species. ... Infraclasses Apogastropoda Cocculiniformia Murchisoniina Neritopsina Vetigastropoda In their work, which has become a standard reference in the field, Ponder and Lindberg (1997) showed that the Orthogastropoda is one of two subclasses of the Gastropoda the class of molluscs, the other subclass being the Eogastropoda. ... Orders Heterostropha Opisthobranchia Pulmonata This article does not cite its references or sources. ... Suborders Systellommatophora Basommatophora Eupulmonata Stylommatophora The Pulmonata are an order (sometimes subclass) of snails and slugs that have developed lungs. ... Suborder Eupulmonata Haszprunar & Huber, 1990 Infraorder Acteophila Dall, 1885 (= formerly Archaeopulmonata) Superfamily Melampoidea Stimpson, 1851 Infraorder Trimusculiformes Minichev & Starobogatov, 1975 Superfamily Trimusculoidea Zilch, 1959 Infraorder Stylommatophora A. Schmidt, 1856 (land snails) Subinfraorder Orthurethra Superfamily Achatinelloidea Gulick, 1873 Superfamily Cochlicopoidea Pilsbry, 1900 Superfamily Partuloidea Pilsbry, 1900 Superfamily Pupilloidea Turton, 1831 Subinfraorder... Anatomy of a slug A slug from North Bend, WA Slugs are gastropod molluscs without shells or with very small internal shells, in contrast to snails, which have a prominent coiled shell. ...