Snail is a general name that is related mainly often to territory of them, terrestrial pulmonate gastropod molluscs. However, the frequent name “snail” is also applied to generally of the elements of the molluscan group Gastropoda that have a curled shell that is big enough for the being to pull back finally into. When the phrase is used in this most common nous, it comprises not just land of the species but as well lots of varieties of sea and freshwater species. Infrequently a few other molluscs that are not really gastropods, such as the Monoplacophora, which apparently look like little limpets, may also casually be demoted to as “snails”. Species like creatures that naturally lack a shell, or have only an internal shell, are usually called slugs, and land species that have only a very small shell (that they cannot retract into) are often called semislugs.