A snail is a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name snail is also used for most of the members of the molluscan class Gastropoda that have a coiled shell that is large enough for the animal to retract completely into. When the word "snail" is used in this most general sense, it includes not just land snails but also numerous species of sea snails and freshwater snails. Gastropods that naturally lack a shell, or have only an internal shell, are mostly called slugs, and land snails that have only a very small shell are often called semi-slugs.
A seashell or sea shell, also known simply as a shell, is a hard, protective outer layer usually created by an animal or organism that lives in the sea. The shell is part of the body of the animal. Empty seashells are often found washed up on beaches by beachcombers. The shells are empty because the animal has died and the soft parts have decomposed or been eaten by another animal.
Gastropods, commonly known as slugs and snails, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda.
Sea slug is a common name for some marine invertebrates with varying levels of resemblance to terrestrial slugs. Most creatures known as sea slugs are gastropods, i.e. they are sea snails that over evolutionary time have either completely lost their shells, or have seemingly lost their shells due to having a greatly reduced or internal shell. The name "sea slug" is most often applied to nudibranchs, as well as to a paraphyletic set of other marine gastropods without obvious shells.
Heterobranchia, the heterobranchs, is a taxonomic clade of snails and slugs, which includes marine, aquatic and terrestrial gastropod mollusks.
A siphon is an anatomical structure which is part of the body of aquatic molluscs in three classes: Gastropoda, Bivalvia and Cephalopoda.
The operculum is a corneous or calcareous anatomical structure like a trapdoor that exists in many groups of sea snails and freshwater snails, and also in a few groups of land snails; the structure is found in some marine and freshwater gastropods, and in a minority of terrestrial gastropods, including the families Helicinidae, Cyclophoridae, Aciculidae, Maizaniidae, Pomatiidae, etc.
Sea snail is a common name for slow-moving marine gastropod molluscs, usually with visible external shells, such as whelk or abalone. They share the taxonomic class Gastropoda with slugs, which are distinguished from snails primarily by the absence of a visible shell.
Cone snails, or cones, are highly venomous sea snails of the family Conidae.
The Trochidae, common name top-snails or top-shells, are a family of various sized sea snails, marine gastropod molluscs in the subclass Vetigastropoda. This family is commonly known as the top-snails because in many species the shell resembles a toy spinning top.
Calliostoma is a genus of small to medium-sized sea snails with gills and an operculum, marine gastropod molluscs within the family Calliostomatidae, the Calliostoma top snails. Previously this genus was placed within the family Trochidae. Calliostoma is the type genus of the family Calliostomatidae.
A micromollusk is a shelled mollusk which is extremely small, even at full adult size. The word is usually, but not exclusively, applied to marine mollusks, although in addition, numerous species of land snails and freshwater mollusks also reach adult size at very small dimensions.
Janthina janthina is a species of holoplanktonic sea snail, a marine gastropod mollusk in the family Epitoniidae. Its common names include violet sea-snail, common violet snail, large violet snail and purple storm snail.
Freshwater snails are gastropod mollusks that live in fresh water. There are many different families. They are found throughout the world in various habitats, ranging from ephemeral pools to the largest lakes, and from small seeps and springs to major rivers. The great majority of freshwater gastropods have a shell, with very few exceptions. Some groups of snails that live in freshwater respire using gills, whereas other groups need to reach the surface to breathe air. In addition, some are amphibious and have both gills and a lung. Most feed on algae, but many are detritivores and some are filter feeders.
Nassarius tritoniformis is a species of sea snail, a marine gastropod mollusc in the family Nassariidae, the nassa mud snails or dog whelks.
Agnewia is a genus of sea snails, marine gastropod mollusks in the family Muricidae, the murex snails or rock snails.
Eupleura is a genus of sea snails, marine gastropod mollusks in the family Muricidae, the murex snails or rock snails.
In the shell of gastropod mollusks, the lip is the free margin of the peristome or aperture of the gastropod shell.
Conus is a genus of predatory sea snails, or cone snails, marine gastropod mollusks in the family Conidae. Prior to 2009, it included all cone snail species but is now more precisely defined, as are other cone snail genera.
Terrestrial molluscs or land molluscs (mollusks) are an ecological group that includes all molluscs that live on land in contrast to freshwater and marine molluscs. They probably first occurred in the Carboniferous, arising from freshwater ones.
