Seashell
Overview
A seashell or sea shell, also known simply as a shell, is a hard, protective outer layer created by an animal that lives in the sea. The shell is part of the body of the animal. Empty seashells are often found washed up on beach
Beach
A beach is a geological landform along the shoreline of an ocean, sea, lake or river. It usually consists of loose particles which are often composed of rock, such as sand, gravel, shingle, pebbles or cobblestones...

es by beachcombers
Beachcombing
Beachcombing and beachcomber are words with multiple, but related, meanings that have evolved over time.A beachcomber is someone who "combs" the beach, and the intertidal zone in general, looking for things of value, interest or utility....

. The shells are empty because the animal has died and the soft parts have been eaten by another animal or have rotted out
Decomposition
Decomposition is the process by which organic material is broken down into simpler forms of matter. The process is essential for recycling the finite matter that occupies physical space in the biome. Bodies of living organisms begin to decompose shortly after death...

.

The term seashell usually refers to the exoskeleton
Exoskeleton
An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Examples of exoskeleton animals include insects such as grasshoppers...

 of an invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...

 (an animal without a backbone).
Discussions
Encyclopedia
A seashell or sea shell, also known simply as a shell, is a hard, protective outer layer created by an animal that lives in the sea. The shell is part of the body of the animal. Empty seashells are often found washed up on beach
Beach
A beach is a geological landform along the shoreline of an ocean, sea, lake or river. It usually consists of loose particles which are often composed of rock, such as sand, gravel, shingle, pebbles or cobblestones...

es by beachcombers
Beachcombing
Beachcombing and beachcomber are words with multiple, but related, meanings that have evolved over time.A beachcomber is someone who "combs" the beach, and the intertidal zone in general, looking for things of value, interest or utility....

. The shells are empty because the animal has died and the soft parts have been eaten by another animal or have rotted out
Decomposition
Decomposition is the process by which organic material is broken down into simpler forms of matter. The process is essential for recycling the finite matter that occupies physical space in the biome. Bodies of living organisms begin to decompose shortly after death...

.

The term seashell usually refers to the exoskeleton
Exoskeleton
An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Examples of exoskeleton animals include insects such as grasshoppers...

 of an invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...

 (an animal without a backbone). Most shells that are found on beaches are the shells of marine
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...

 mollusks ("molluscs" in British English
British English
British English, or English , is the broad term used to distinguish the forms of the English language used in the United Kingdom from forms used elsewhere...

), partly because many of these shells endure better than other seashells.

Apart from mollusk shell
Mollusc shell
The mollusc shell is typically a calcareous exoskeleton which encloses, supports and protects the soft parts of an animal in the phylum Mollusca, which includes snails, clams, tusk shells, and several other classes...

s, other shells that can be found on beaches are those of barnacle
Barnacle
A barnacle is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile suspension feeders, and have...

s, horseshoe crab
Horseshoe crab
The Atlantic horseshoe crab, Limulus polyphemus, is a marine chelicerate arthropod. Despite its name, it is more closely related to spiders, ticks, and scorpions than to crabs. Horseshoe crabs are most commonly found in the Gulf of Mexico and along the northern Atlantic coast of North America...

s and brachiopod
Brachiopod
Brachiopods are a phylum of marine animals that have hard "valves" on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, while the front can be opened for feeding or closed for protection...

s. Marine annelid
Annelid
The annelids , formally called Annelida , are a large phylum of segmented worms, with over 17,000 modern species including ragworms, earthworms and leeches...

 worms in the family Serpulidae
Serpulidae
Serpulidae is a family of sessile, tube-building annelid worms in the class Polychaeta. The members of this family differ from the sabellid tube worms in that they have a specialized operculum that blocks the entrance of their tubes when they withdraw into the tubes. In addition, serpulids secrete...

 create shells made of calcareous tubes cemented onto other surfaces. The shells of sea urchin
Sea urchin
Sea urchins or urchins are small, spiny, globular animals which, with their close kin, such as sand dollars, constitute the class Echinoidea of the echinoderm phylum. They inhabit all oceans. Their shell, or "test", is round and spiny, typically from across. Common colors include black and dull...

s are called tests, and the moulted shells of crab
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...

s and lobster
Lobster
Clawed lobsters comprise a family of large marine crustaceans. Highly prized as seafood, lobsters are economically important, and are often one of the most profitable commodities in coastal areas they populate.Though several groups of crustaceans are known as lobsters, the clawed lobsters are most...

s are called exuviae. While most seashells are external, some cephalopods have internal shells.

Seashells have been admired, studied and used by humans for many different purposes throughout history and pre-history. But seashells are not the only kind of shells. In a variety of habitats it is possible to find shells from freshwater animals such as freshwater mussels and freshwater snail
Freshwater snail
A freshwater snail is one kind of freshwater mollusc, the other kind being freshwater clams and mussels, i.e. freshwater bivalves. Specifically a freshwater snail is a gastropod that lives in a watery non-marine habitat. The majority of freshwater gastropods have a shell, with very few exceptions....

s, and it is also possible to find shells from land snail
Land snail
A land snail is any of the many species of snail that live on land, as opposed to those that live in salt water and fresh water. Land snails are terrestrial gastropod mollusks that have shells, It is not always an easy matter to say which species are terrestrial, because some are more or less...

s.

Terminology

When the word "seashells" is used to refer only to the shells of marine mollusks then studying seashells is part of conchology
Conchology
Conchology is the scientific or amateur study of mollusc shells. Conchology is one aspect of malacology, the study of molluscs, however malacology studies molluscs as whole organisms, not just their shells. Conchology pre-dated malacology as a field of study. It includes the study of land and...

. Conchologists or serious collectors who have a scientific bias are in general careful not to disturb living populations and habitats: even though they may collect a few live animals, most responsible collectors do not often over-collect or otherwise disturb ecosystems.

When studying the whole molluscan animal is included as well as studying the shell, then the study is known as malacology
Malacology
Malacology is the branch of invertebrate zoology which deals with the study of the Mollusca , the second-largest phylum of animals in terms of described species after the arthropods. Mollusks include snails and slugs, clams, octopus and squid, and numerous other kinds, many of which have shells...

; a person who studies mollusks is known as a malacologist.

Finding seashells

Seashells are commonly found in beach drift, which is natural detritus deposited along strandlines on beach
Beach
A beach is a geological landform along the shoreline of an ocean, sea, lake or river. It usually consists of loose particles which are often composed of rock, such as sand, gravel, shingle, pebbles or cobblestones...

es by the wave
Wave
In physics, a wave is a disturbance that travels through space and time, accompanied by the transfer of energy.Waves travel and the wave motion transfers energy from one point to another, often with no permanent displacement of the particles of the medium—that is, with little or no associated mass...

s and the tide
Tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....

s. Shells are very often washed up onto a beach empty and clean, the animal having already died, and the soft parts having rotted away or having been eaten by either predators or scavenger
Scavenger
Scavenging is both a carnivorous and herbivorous feeding behavior in which individual scavengers search out dead animal and dead plant biomass on which to feed. The eating of carrion from the same species is referred to as cannibalism. Scavengers play an important role in the ecosystem by...

s.

Empty seashells are often picked up by beachcombers, and collecting these shells is a harmless hobby
Hobby
A hobby is a regular activity or interest that is undertaken for pleasure, typically done during one's leisure time.- Etymology :A hobby horse is a wooden or wickerwork toy made to be ridden just like a real horse...

 or study. However, the majority of seashells which are offered for sale commercially have been collected alive (often in bulk) and then killed and cleaned, specifically for the commercial trade. This type of large-scale exploitation can sometimes have a strong negative impact on local ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....

s, and sometimes can significantly reduce the distribution of rare species
Rare species
A rare species is a group of organisms that are very uncommon or scarce. This designation may be applied to either a plant or animal taxon, and may be distinct from the term "endangered" or "threatened species" but not "extinct"....

.

Molluscan seashells

The word seashell is often used to mean only the shell of a marine
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...

 mollusk. Marine mollusk shells that are familiar to beachcombers and thus most likely to be called "seashells" are the shells of marine species of bivalves (or clam
Clam
The word "clam" can be applied to freshwater mussels, and other freshwater bivalves, as well as marine bivalves.In the United States, "clam" can be used in several different ways: one, as a general term covering all bivalve molluscs...

s), gastropods (or snail
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...

s), scaphopods (or tusk shell
Tusk shell
The tusk shells or scaphopods are a class of shelled marine mollusks. The scientific name of this class is Scaphopoda, meaning "shovel-footed". Shells of species within this class range from about 0.5 to 15 cm in length...

s), polyplacophorans (or chiton
Chiton
Chitons are small to large, primitive marine molluscs in the class Polyplacophora.There are 900 to 1,000 extant species of chitons in the class, which was formerly known as Amphineura....

s), and cephalopod
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...

s (such as nautilus
Nautilus
Nautilus is the common name of marine creatures of cephalopod family Nautilidae, the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina. It comprises six living species in two genera, the type of which is the genus Nautilus...

 and spirula). These shells are very often the most commonly encountered, both in the wild, and for sale as decorative objects.

Marine species of gastropods and bivalves are more numerous than land and freshwater species, and the shells are often larger and more robust. The shells of marine species also often have more sculpture
Sculpture (mollusc)
The sculpture of a mollusc shell is the three-dimensional ornamentation on the outer surface, as distinct from the basic shape of the shell itself or colouration. Sculpture may be concave as well as convex. Sometimes it has microscopic detail. Sculpture refers to the calcareous outer layer, not the...

 and more color, although this is by no means always the case.

In the tropical and sub-tropical areas of the planet, there are far more species of colorful, large, shallow water shelled marine mollusks than there are in the temperate zones and the regions closer to the poles.

Although there are a number of species of shelled mollusks that are quite large, there are vast numbers of extremely small species too, see micromollusk
Micromollusk
A micromollusk is a descriptive term for 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...

s.

Not all mollusks are marine however, there are numerous land and freshwater mollusks, see for example snail
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...

 and freshwater bivalves
Freshwater bivalves
Freshwater bivalves are one kind of freshwater molluscs. They are bivalves which live in freshwater, as opposed to saltwater. Although the majority of species of bivalve molluscs live in the sea, a number of different families of bivalves live in freshwater...

. And not all mollusks have an external shell: some mollusks such as some cephalopods (squid and octopuses) have an internal shell, and many mollusks have no shell, see for example slug
Slug
Slug is a common name that is normally applied to any gastropod mollusc that lacks a shell, has a very reduced shell, or has a small internal shell...

 and nudibranch
Nudibranch
A nudibranch is a member of what is now a taxonomic clade, and what was previously a suborder, of soft-bodied, marine gastropod mollusks which shed their shell after their larval stage. They are noted for their often extraordinary colors and striking forms...

.

Bivalves

Bivalves are often the most common seashells that wash up on large sandy beaches or in sheltered lagoon
Lagoon
A lagoon is a body of shallow sea water or brackish water separated from the sea by some form of barrier. The EU's habitat directive defines lagoons as "expanses of shallow coastal salt water, of varying salinity or water volume, wholly or partially separated from the sea by sand banks or shingle,...

s. They can sometimes be extremely numerous. Very often the two valves become separated.

Shell Beach, Western Australia
Shell Beach, Western Australia
Shell Beach is a beach in the Shark Bay region of Western Australia, 45 kilometres south-east of Denham.It covers a 110 km long stretch of coast along the L'Haridon Bight. It is one of only two beaches in the world made entirely from shells....

 is a beach which is entirely made up of the shells of the cockle
Cockle (bivalve)
Cockle is the common name for a group of small, edible, saltwater clams, marine bivalve molluscs in the family Cardiidae.Various species of cockles live in sandy sheltered beaches throughout the world....

 Fragum erugatum as shown here.

Gastropods

Certain species of gastropod seashells (the shells of sea snail
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...

s) can sometimes be common, washed up on sandy beaches, and also on beaches that are surrounded by rocky marine habitat.

Polyplacophorans

Chiton
Chiton
Chitons are small to large, primitive marine molluscs in the class Polyplacophora.There are 900 to 1,000 extant species of chitons in the class, which was formerly known as Amphineura....

 plates or valves often wash up on beaches in rocky areas where chitons are common. Chiton shells, which are composed of eight separate plates and a girdle, usually come apart not long after death, so they are almost always found as disarticulated plates. Plates from larger species of chitons are sometimes known as "butterfly shells" because of their shape.

Cephalopods

Only a few species of cephalopod
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...

s have shells (either internal or external) that are sometimes found washed up on beaches.

Some cephalopod
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...

s such as Sepia
Sepia (genus)
Sepia is a genus of cuttlefish in the family Sepiidae encompassing some of the best known and most common species. The cuttlebone is relatively ellipsoid in shape...

, the cuttlefish, have a large internal shell, the cuttlefish bone, and this often washes up on beaches in parts of the world where cuttlefish are common.

Spirula spirula is a deep water squid-like cephalopod. It has an internal shell which is small (about 1 in or 24 mm) but very light and buoyant. This chambered shell floats very well and therefore washes up easily and is familiar to beachcombers in the tropics.

Nautilus
Nautilus
Nautilus is the common name of marine creatures of cephalopod family Nautilidae, the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina. It comprises six living species in two genera, the type of which is the genus Nautilus...

is the only genus of cephalopod that has a well-developed external shell. Females of the cephalopod genus Argonauta
Argonaut (animal)
The argonauts are a group of pelagic octopuses. They are also called paper nautiluses, referring to the paper-thin eggcase that females secrete...

create a papery egg case which sometimes washes up on tropical beaches and is referred to as a "paper nautilus".

The largest group of shelled cephalopods, the ammonite
Ammonite
Ammonite, as a zoological or paleontological term, refers to any member of the Ammonoidea an extinct subclass within the Molluscan class Cephalopoda which are more closely related to living coleoids Ammonite, as a zoological or paleontological term, refers to any member of the Ammonoidea an extinct...

s, are extinct, but their shells are very common in certain areas as fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

s.

Molluscan seashells used by other animals

Empty molluscan seashells are a sturdy, and usually readily available, "free" resource which is often easily found on beaches, in the intertidal zone
Intertidal zone
The intertidal zone is the area that is above water at low tide and under water at high tide . This area can include many different types of habitats, with many types of animals like starfish, sea urchins, and some species of coral...

, and in the shallow subtidal zone. As such they are sometimes used second-hand
Second-Hand
Second-Hand was a 2005 Romanian film directed by Dan Piţa.-Plot summary:The film's plot surrounds the romantic involvement of two contrasting characters: Petre , a Mafioso, and Andreea , a young violin player. The pair meet and fall in love...

 by animals other than humans for various purposes, including for protection (as in hermit crab
Hermit crab
Hermit crabs are decapod crustaceans of the superfamily Paguroidea. Most of the 1100 species possess an asymmetrical abdomen which is concealed in an empty gastropod shell that is carried around by the hermit crab.-Description:...

s) and for construction.

By other mollusks

  • Carrier shells in the family Xenophoridae
    Xenophoridae
    Xenophoridae, common name carrier shells, are a taxonomic family of medium-sized to large sea snails, marine gastropod mollusks in the clade Littorinimorpha....

     are marine shelled gastropods, fairly large sea snails. Most species of xenophorids cement a series of objects to the rim of their shells as they grow. These objects are sometimes small pebbles or other hard detritus. Very often shells of bivalves or smaller gastropods are used, depending on what is available on the particular substrate
    Substrate (biology)
    In biology a substrate is the surface a plant or animal lives upon and grows on. A substrate can include biotic or abiotic materials and animals. For example, encrusting algae that lives on a rock can be substrate for another animal that lives on top of the algae. See also substrate .-External...

     where the snail itself lives. It is not clear whether these shell attachments serve as camouflage
    Camouflage
    Camouflage is a method of concealment that allows an otherwise visible animal, military vehicle, or other object to remain unnoticed, by blending with its environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly...

    , or whether they are intended to help prevent the shell sinking into a soft substrate
    Substrate (biology)
    In biology a substrate is the surface a plant or animal lives upon and grows on. A substrate can include biotic or abiotic materials and animals. For example, encrusting algae that lives on a rock can be substrate for another animal that lives on top of the algae. See also substrate .-External...

    .


  • Small octopus
    Octopus
    The octopus is a cephalopod mollusc of the order Octopoda. Octopuses have two eyes and four pairs of arms, and like other cephalopods they are bilaterally symmetric. An octopus has a hard beak, with its mouth at the center point of the arms...

    es sometimes use an empty shell as a sort of cave to hide in, or hold seashells around themselves as a form of protection like a temporary fortress.

By other invertebrates

  • Almost all genera of hermit crab
    Hermit crab
    Hermit crabs are decapod crustaceans of the superfamily Paguroidea. Most of the 1100 species possess an asymmetrical abdomen which is concealed in an empty gastropod shell that is carried around by the hermit crab.-Description:...

    s use or "wear" empty marine gastropod shells throughout their lifespan, in order to protect their soft abdomens, and in order to have a strong shell to withdraw into if attacked by a predator. Each individual hermit crab is forced to find another gastropod shell on a regular basis, whenever it grows too large for the one it is currently using.

Some hermit crab species live on land and may be found quite some distance from the sea, including those in the tropical genus Coenobita
Coenobita
The genus Coenobita contains the sixteen species of terrestrial hermit crabs. The majority of the species are found in the Indo-Pacific region, with only one species in West Africa, one species occurring along the western Atlantic Ocean, and one species occurring on the Pacific coast of the Americas...

.

Collecting shells as a hobby and a study

There are numerous popular books and field guide
Field guide
A field guide is a book designed to help the reader identify wildlife or other objects of natural occurrence . It is generally designed to be brought into the 'field' or local area where such objects exist to help distinguish between similar objects...

s on the subject of shell-collecting. Although there are a number of books about land and freshwater mollusks, the majority of popular books emphasize, or focus exclusively on, the shells of marine mollusks. Both the science of studying mollusk shells and the hobby of collecting and classifying them are known as conchology
Conchology
Conchology is the scientific or amateur study of mollusc shells. Conchology is one aspect of malacology, the study of molluscs, however malacology studies molluscs as whole organisms, not just their shells. Conchology pre-dated malacology as a field of study. It includes the study of land and...

. The line between professionals and amateur enthusiasts is often not well defined in this subject, because many amateurs have contributed to, and continue to contribute to, conchology and the larger science of malacology
Malacology
Malacology is the branch of invertebrate zoology which deals with the study of the Mollusca , the second-largest phylum of animals in terms of described species after the arthropods. Mollusks include snails and slugs, clams, octopus and squid, and numerous other kinds, many of which have shells...

. Many shell collectors belong to "shell clubs" where they can meet others who share their interests. A large number of amateurs collect the shells of marine mollusks, and this is partly because many shells wash up empty on beaches, or live in the intertidal or sub-tidal zones, and are therefore easily found and preserved without much in the way of specialized equipment or expensive supplies. Some shell collectors find their own material and keep careful records, or buy only "specimen shells", which means shells which have full collecting data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...

: information including how, when, where, in what habitat, and by whom, the shells were collected. On the other hand, some collectors buy the more widely available commercially-imported exotic shells, the majority of which have very little data, or none at all. To museum
Museum
A museum is an institution that cares for a collection of artifacts and other objects of scientific, artistic, cultural, or historical importance and makes them available for public viewing through exhibits that may be permanent or temporary. Most large museums are located in major cities...

 scientists, having full collecting data (when, where, and by whom it was collected) with a specimen is far more important than having the shell correctly identified. Some owners of shell collections hope to be able to donate their collection to a major natural history or zoology museum
Museum
A museum is an institution that cares for a collection of artifacts and other objects of scientific, artistic, cultural, or historical importance and makes them available for public viewing through exhibits that may be permanent or temporary. Most large museums are located in major cities...

 at some point, however, shells with little or no collecting data are usually of no value to science, and are likely not to be accepted by a major museum. Apart from any damage to the shell that may have happened before it was collected, shells can also suffer damage when they are stored or displayed. For an example of one rather serious kind of damage see Byne's disease
Byne's disease
Byne's disease, more accurately known as Bynesian decay, is a peculiar and permanently damaging condition which often attacks mollusk shells that are in storage or on display for long periods of time....

.
Shell clubs

There are a number of clubs or societies which consist of people who are united by a shared interest in shells. In the USA these clubs are more common in southerly coastal areas, such as Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...

 and California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

, where the marine fauna is rich in species.
Identification

Seashells are usually identified by consulting general or regional shell-collecting field guide
Field guide
A field guide is a book designed to help the reader identify wildlife or other objects of natural occurrence . It is generally designed to be brought into the 'field' or local area where such objects exist to help distinguish between similar objects...

s, and specific scientific books on different taxa of shell-bearing mollusks (monograph
Monograph
A monograph is a work of writing upon a single subject, usually by a single author.It is often a scholarly essay or learned treatise, and may be released in the manner of a book or journal article. It is by definition a single document that forms a complete text in itself...

s) or "iconographies" (limited text - mainly photographs or other illustrations). (For a few titles on this subject in the USA, see the list of books at the foot of this article.) Identifications to the species level are generally achieved by examining illustrations and written descriptions, rather than by the use of Identification key
Identification key
In biology, an identification key is a printed or computer-aided device that aids the identification of biological entities, such as plants, animals, fossils, microorganisms, and pollen grains...

s, as is often the case in identifying plants and other phyla of invertebrates. The construction of functional keys for the identification of the shells of marine mollusks to the species level can be very difficult, because of the great variability within many species and families. The identification of certain individual species is often very difficult, even for a specialist in that particular family. Some species cannot be differentiated on the basis of shell character alone.

Numerous smaller and more obscure mollusk species (see micromollusk
Micromollusk
A micromollusk is a descriptive term for 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...

) are yet to be discovered and named. In other words, they have not yet been differentiated from similar species and assigned scientific (binomial) names in articles in journals recognized by the International Commission on Zoological Nomenclature
International Commission on Zoological Nomenclature
The International Commission on Zoological Nomenclature is an organization dedicated to "achieving stability and sense in the scientific naming of animals". Founded in 1895, it currently comprises 28 members from 20 countries, mainly practicing zoological taxonomists...

 (ICZN). Large numbers of new species are published in the scientific literature each year. There are currently an estimated 100,000 species of mollusks worldwide.
Non-marine "seashells"

The term seashell is also applied loosely to mollusk shells that are not of marine origin, for example by people walking the shores of lakes and rivers using the term for the freshwater mollusk
Freshwater mollusc
Freshwater molluscs are those members of the Phylum Mollusca which live in freshwater habitats, both lotic such as rivers, streams, canals, springs, and underground cave streams and lentic such as lakes, ponds , and ditches.This article is about freshwater Mollusca in general; for information on...

 shells they encounter. Seashells purchased from tourist shops or dealers may include various freshwater and terrestrial shells as well. Non-marine items offered may include large and colorful tropical land snail
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...

 shells, freshwater apple snail shells, and pearly freshwater unionid mussel shells. This can be confusing to collectors, as non-marine shells are often not included in their reference books.

As currency

Seashells have been used as a medium of exchange in various places, including many Indian Ocean and Pacific Ocean islands, also in North America, Africa and the Caribbean.
  • The most common species of shells to be used as currency have been Cypraea moneta
    Cypraea moneta
    Monetaria moneta, commonly known as the money cowry, is a species of small sea snail, a marine gastropod mollusk in the family Cypraeidae, the cowries....

    , the "money cowry
    Cowry
    Cowry, also sometimes spelled cowrie, plural cowries, is the common name for a group of small to large sea snails, marine gastropod molluscs in the family Cypraeidae, the cowries...

    ", and certain tusk shell
    Tusk shell
    The tusk shells or scaphopods are a class of shelled marine mollusks. The scientific name of this class is Scaphopoda, meaning "shovel-footed". Shells of species within this class range from about 0.5 to 15 cm in length...

    s or dentalium, such as those used in North Western North America for many centuries.
  • Some tribes of the indigenous peoples of the Americas
    Indigenous peoples of the Americas
    The indigenous peoples of the Americas are the pre-Columbian inhabitants of North and South America, their descendants and other ethnic groups who are identified with those peoples. Indigenous peoples are known in Canada as Aboriginal peoples, and in the United States as Native Americans...

     used shells for wampum
    Wampum
    Wampum are traditional, sacred shell beads of the Eastern Woodlands tribes of the indigenous people of North America. Wampum include the white shell beads fashioned from the North Atlantic channeled whelk shell; and the white and purple beads made from the quahog, or Western North Atlantic...

     and hair pipe
    Hair pipe
    A Hair Pipe is a term for a wide slim bead, more than 1.5 inches wide, which were popular with American Indians, particularly from the Great Plains and Northwest Plateau....

    s. The Native American wampum
    Wampum
    Wampum are traditional, sacred shell beads of the Eastern Woodlands tribes of the indigenous people of North America. Wampum include the white shell beads fashioned from the North Atlantic channeled whelk shell; and the white and purple beads made from the quahog, or Western North Atlantic...

     belts
    were made of the shell of the quahog clam.
  • It is of historic interest that the Dutch East India Company
    Dutch East India Company
    The Dutch East India Company was a chartered company established in 1602, when the States-General of the Netherlands granted it a 21-year monopoly to carry out colonial activities in Asia...

    , a major force in the colonization of the Indian and Pacific Oceans, amassed a large portion of its vast fortune via trading shell money of the species Cypraea moneta
    Cypraea moneta
    Monetaria moneta, commonly known as the money cowry, is a species of small sea snail, a marine gastropod mollusk in the family Cypraeidae, the cowries....

    and Cypraea annulus, in exchange for commodities such as spice
    Spice
    A spice is a dried seed, fruit, root, bark, or vegetative substance used in nutritionally insignificant quantities as a food additive for flavor, color, or as a preservative that kills harmful bacteria or prevents their growth. It may be used to flavour a dish or to hide other flavours...

    s, exotic animals, and gemstone
    Gemstone
    A gemstone or gem is a piece of mineral, which, in cut and polished form, is used to make jewelry or other adornments...

    s, all of which were considered valuable in Europe at the time.

As tools

Seashells have often been used as tool
Tool
A tool is a device that can be used to produce an item or achieve a task, but that is not consumed in the process. Informally the word is also used to describe a procedure or process with a specific purpose. Tools that are used in particular fields or activities may have different designations such...

s, because of their strength and the variety of their shapes.
  • Giant clam
    Giant clam
    The giant clam, Tridacna gigas , is the largest living bivalve mollusc. T. gigas is one of the most endangered clam species. It was mentioned as early as 1825 in scientific reports...

    s (Family Tridacnidae) have been used as bowls, and when big enough, even as bathtubs and baptism
    Baptism
    In Christianity, baptism is for the majority the rite of admission , almost invariably with the use of water, into the Christian Church generally and also membership of a particular church tradition...

    al fonts.
  • Melo melo
    Melo melo
    Melo melo, common name the Indian volute or bailer shell, is a very large sea snail, a marine gastropod mollusc in the family Volutidae, the volutes.-Distribution:...

    , the "bailer volute
    Volutidae
    Volutidae, common name volutes, are a taxonomic family of predatory sea snails that range in size from 9 mm to over 500 mm, marine gastropod mollusks...

    ", is so named because Native Australians used it to bail out their canoes.
  • Many different species of bivalves have been used as scrapers, blades, clasps, and other such tools, due to their shape.
  • Some marine gastropods have been used for oil lamp
    Oil lamp
    An oil lamp is an object used to produce light continuously for a period of time using an oil-based fuel source. The use of oil lamps began thousands of years ago and is continued to this day....

    s, the oil being poured in the aperture of the shell, and the siphonal canal
    Siphonal canal
    Some sea marine gastropods have a soft tubular anterior extension of the mantle called a siphon through which water is drawn into the mantle cavity and over the gill and which serves as a chemoreceptor to locate food. In many carnivorous snails, where the siphon is particularly long, the structure...

     serving as a holder for the wick.

In horticulture

Because seashells are in some areas a readily available bulk source of calcium carbonate, shells such as oyster
Oyster
The word oyster is used as a common name for a number of distinct groups of bivalve molluscs which live in marine or brackish habitats. The valves are highly calcified....

 shells are sometimes used as soil conditioners in horticulture
Horticulture
Horticulture is the industry and science of plant cultivation including the process of preparing soil for the planting of seeds, tubers, or cuttings. Horticulturists work and conduct research in the disciplines of plant propagation and cultivation, crop production, plant breeding and genetic...

. The shells are broken or ground into small pieces in order to have the desired effect of raising the pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

 and increasing the calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

 content in the soil.

In religion and spirituality

Seashells have played a part in religion and spirituality, sometimes even as ritual objects.
  • In Christianity, the scallop
    Scallop
    A scallop is a marine bivalve mollusk of the family Pectinidae. Scallops are a cosmopolitan family, found in all of the world's oceans. Many scallops are highly prized as a food source...

     shell is considered to be the symbol of Saint James the Great
    Saint James the Great
    James, son of Zebedee was one of the Twelve Apostles of Jesus. He was a son of Zebedee and Salome, and brother of John the Apostle...

    , see Pecten jacobaeus
    Pecten jacobaeus
    Pecten jacobaeus is a species of scallop, an edible saltwater clam, a marine bivalve mollusc in the family Pectinidae, the scallops.This species appears to be endemic to the Mediterranean Sea, but it may in fact be conspecific with Pecten maximus, the great scallop, which has a larger distribution...

    .
  • In Hinduism
    Hinduism
    Hinduism is the predominant and indigenous religious tradition of the Indian Subcontinent. Hinduism is known to its followers as , amongst many other expressions...

     left-handed shells of Turbinella pyrum
    Turbinella pyrum
    Turbinella pyrum, common names the chank shell, sacred chank or chank, also known as the divine conch, sometimes referred to simply as a conch, is a species of very large sea snail with a gill and an operculum, a marine gastropod mollusk in the family Turbinellidae...

    (the sacred shankha
    Shankha
    Shankha bhasam , also spelled and pronounced as Shankh and Sankha, is a conch shell of ritual and religious importance in Hinduism and Buddhism. It is the shell of a large predatory sea snail,Turbinella pyrum found in the Indian Ocean....

    ) are considered to be sacred to the god Vishnu
    Vishnu
    Vishnu is the Supreme god in the Vaishnavite tradition of Hinduism. Smarta followers of Adi Shankara, among others, venerate Vishnu as one of the five primary forms of God....

    . The person who finds a left-handed chank shell (one that coils to the left) is sacred to Vishnu, as well. The chank shell also plays an important role in Buddhism
    Buddhism
    Buddhism is a religion and philosophy encompassing a variety of traditions, beliefs and practices, largely based on teachings attributed to Siddhartha Gautama, commonly known as the Buddha . The Buddha lived and taught in the northeastern Indian subcontinent some time between the 6th and 4th...

    .
  • Cowries have often been considered to be symbols of female fertility. They were often treated as actual fertility charms
    Amulet
    An amulet, similar to a talisman , is any object intended to bring good luck or protection to its owner.Potential amulets include gems, especially engraved gems, statues, coins, drawings, pendants, rings, plants and animals; even words said in certain occasions—for example: vade retro satana—, to...

    . The dorsum of the shell resembles a pregnant belly, and the underside of the shell resembles a vulva
    Vulva
    The vulva consists of the external genital organs of the female mammal. This article deals with the vulva of the human being, although the structures are similar for other mammals....

    . In the South Indian state of Kerala, cowries are used for making astrological predictions.
  • In Santería
    Santería
    Santería is a syncretic religion of West African and Caribbean origin influenced by Roman Catholic Christianity, also known as Regla de Ocha, La Regla Lucumi, or Lukumi. Its liturgical language, a dialect of Yoruba, is also known as Lucumi....

    , shells are used for divination purposes.
  • The Moche
    Moche
    'The Moche civilization flourished in northern Peru from about 100 AD to 800 AD, during the Regional Development Epoch. While this issue is the subject of some debate, many scholars contend that the Moche were not politically organized as a monolithic empire or state...

     culture of ancient Peru
    Peru
    Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....

     worshipped animals and the sea, and often depicted shells in their art.

As musical instruments

Seashells have been used as musical instruments, wind instruments for many hundreds if not thousands of years. Most often the shells of large sea snails are used, as trumpets, by cutting a hole in the spire
Spire (mollusc)
A spire is a descriptive term for part of the coiled shell of mollusks. The word is a convenient aid in describing shells, but it does not refer to a very precise part of shell anatomy: the spire consists of all of the whorls except for the body whorl...

 of the shell, or cutting off the tip of the spire altogether. Various different kinds of large marine gastropod shells can be turned into "blowing shells", however the most commonly encountered species used as "conch
Conch
A conch is a common name which is applied to a number of different species of medium-sized to large sea snails or their shells, generally those which are large and have a high spire and a siphonal canal....

" trumpets are:
  • The sacred chank, Turbinella pyrum
    Turbinella pyrum
    Turbinella pyrum, common names the chank shell, sacred chank or chank, also known as the divine conch, sometimes referred to simply as a conch, is a species of very large sea snail with a gill and an operculum, a marine gastropod mollusk in the family Turbinellidae...

    , known in India as the shankha
    Shankha
    Shankha bhasam , also spelled and pronounced as Shankh and Sankha, is a conch shell of ritual and religious importance in Hinduism and Buddhism. It is the shell of a large predatory sea snail,Turbinella pyrum found in the Indian Ocean....

    . In Tibet
    Tibet
    Tibet is a plateau region in Asia, north-east of the Himalayas. It is the traditional homeland of the Tibetan people as well as some other ethnic groups such as Monpas, Qiang, and Lhobas, and is now also inhabited by considerable numbers of Han and Hui people...

     it is known as "dung-dkar".

  • The Triton shell
    Triton (mollusk)
    Triton is the common name given to a number of very large sea snails, predatory marine gastropods in the genus Charonia. The name "triton" is also often applied as part of the common name, to other, much smaller sea snails of other genera within the same family, Ranellidae.Tritons are named after...

     also known as "Triton's trumpet" Charonia tritonis
    Charonia tritonis
    Charonia tritonis, common name Triton's trumpet, is a species of very large sea snail, a marine gastropod mollusc in the family Ranellidae, the tritons.Also see Charonia or Triton .-Distribution:...

    which is used as a trumpet in Melanesian and Polynesian culture and also in Korea
    Korea
    Korea ) is an East Asian geographic region that is currently divided into two separate sovereign states — North Korea and South Korea. Located on the Korean Peninsula, Korea is bordered by the People's Republic of China to the northwest, Russia to the northeast, and is separated from Japan to the...

     and Japan. In Japan this kind of trumpet is known as the horagai
    Horagai
    ' are large conch shells that have been used as a trumpets in Japan for many centuries. The instrument, which has served a number of purposes throughout Japanese history, has been given a number of Japanese names depending on its function...

    . In Korea it is known as the nagak
    Nagak
    The nagak is a large seashell played as a horn in Korean traditional music. It produces only a single tone and is used primarily in the military procession music called daechwita....

    . In some Polynesian islands it is known as "pu". http://www.furious.com/perfect/shells.html
  • The Queen Conch Strombus gigas
    Strombus gigas
    Lobatus gigas, commonly known as the queen conch, is a species of large edible sea snail, a marine gastropod mollusk in the family of true conchs, the Strombidae...

    , is or was sometimes used as a trumpet in the Caribbean.

In personal adornment

Whole seashells or parts of sea shells have been used as jewelry or in other forms of adornment since prehistoric times. Mother of pearl was historically primarily a seashell product, although more recently some mother of pearl comes from freshwater mussels. Also see pearl
Pearl
A pearl is a hard object produced within the soft tissue of a living shelled mollusk. Just like the shell of a mollusk, a pearl is made up of calcium carbonate in minute crystalline form, which has been deposited in concentric layers. The ideal pearl is perfectly round and smooth, but many other...

.
  • Shell necklaces have been found in Stone Age graves as far inland as the Dordogne
    Dordogne
    Dordogne is a départment in south-west France. The départment is located in the region of Aquitaine, between the Loire valley and the High Pyrénées named after the great river Dordogne that runs through it...

     Valley in France.
  • Seashells are often used whole and drilled, so that they can be threaded like bead
    Bead
    A bead is a small, decorative object that is usually pierced for threading or stringing. Beads range in size from under to over in diameter. A pair of beads made from Nassarius sea snail shells, approximately 100,000 years old, are thought to be the earliest known examples of jewellery. Beadwork...

    s, or cut into pieces of various shapes. Sometimes shells can be found that are already "drilled" by predatory snails of the family Naticidae
    Naticidae
    Naticidae, common name the moon snails, is a family of minute to large-sized predatory sea snails, marine gastropod molluscs in the clade Littorinimorpha.Naticidae is the only family in the superfamily Naticoidea....

    . Fine whole shell necklaces were made by Tasmanian Aboriginal women for more than 2,600 years. The necklaces represent a significant cultural tradition which is still practised by Palawa women elders. The shells used include pearly green and blue-green maireener (rainbow kelp) shells, brown and white rice shells, black cats' teeth shells and pink button shells.
  • Naturally-occurring, beachworn, cone shell "tops" (the broken-off spire of the shell, which often has a hole worn at the tip) can function as beads without any further modification. In Hawaii
    Hawaii
    Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...

     these natural beads were traditionally collected from the beach drift in order to make puka shell
    Puka shell
    Puka shells originally were naturally occurring bead-like objects which could be found on some beaches in Hawaii. These were beachworn pieces of cone snail shells, a kind of seashell. Puka is the Hawaiian word for "hole" and refers to the naturally occurring hole in the middle of these rounded...

     jewelry. Since it is hard to obtain large quantities of naturally-occurring beachworn cone tops, almost all modern puka shell jewelry uses cheaper imitations, cut from thin shells of other species of mollusk, or even made of plastic.
  • Shells historically have been and still are made into, or incorporated into, necklaces, pendants, beads, earrings, button
    Button
    In modern clothing and fashion design, a button is a small fastener, most commonly made of plastic, but also frequently of seashell, which secures two pieces of fabric together. In archaeology, a button can be a significant artifact. In the applied arts and in craft, a button can be an example of...

    s, brooch
    Brooch
    A brooch ; also known in ancient times as a fibula; is a decorative jewelry item designed to be attached to garments. It is usually made of metal, often silver or gold but sometimes bronze or some other material...

    es, ring
    Ring (finger)
    A finger ring is a circular band worn as a type of ornamental jewelry around a finger; it is the most common current meaning of the word ring. Other types of metal bands worn as ornaments are also called rings, such as arm rings and neck rings....

    s, hair combs
    Comb
    A comb is a toothed device used in hair care for straightening and cleaning hair or other fibres. Combs are among the oldest tools found by archaeologists...

    , belt buckles and other uses.
  • The shell of the large "bullmouth helmet" sea snail, scientific name Cypraecassis rufa
    Cypraecassis rufa
    Cypraecassis rufa is a species of large sea snail, a marine gastropod mollusk in the family Cassidae. It is commonly known as the bullmouth or red helmet shell, and also as the cameo shell.-Distribution:...

    , was historically, and still is, used to make valuable cameos.
  • Mother of pearl
    Nacre
    Nacre , also known as mother of pearl, is an organic-inorganic composite material produced by some mollusks as an inner shell layer; it is also what makes up pearls. It is very strong, resilient, and iridescent....

     from many seashells including species in the family Trochidae
    Trochidae
    The Trochidae, common name top snails, are a taxonomic family of very small to large sea snails, marine gastropod molluscs in the clade Vetigastropoda ....

    , Turbinidae
    Turbinidae
    Turbinidae, the turban snails, are a family of small to large marine gastropods. Turbinidae have a strong, thick calcareous operculum readily distinguishing them from the somewhat similar Trochidae or top snails, which have a corneous operculum...

    , Haliotidae, and various pearly bivalves, has often been used in jewelry, buttons, etc.
  • In London, Pearly Kings and Queens
    Pearly Kings and Queens
    Pearly Kings and Queens, known as pearlies, are an organised charitable tradition of working class culture in London, England.The practice of wearing clothes decorated with pearl buttons originated in the 19th century. It is first associated with Henry Croft, an orphan street sweeper who collected...

     traditionally wear clothing covered in patterns made up of hundreds of "pearl button
    Button
    In modern clothing and fashion design, a button is a small fastener, most commonly made of plastic, but also frequently of seashell, which secures two pieces of fabric together. In archaeology, a button can be a significant artifact. In the applied arts and in craft, a button can be an example of...

    s", in other words, buttons made of mother-of-pearl or nacre
    Nacre
    Nacre , also known as mother of pearl, is an organic-inorganic composite material produced by some mollusks as an inner shell layer; it is also what makes up pearls. It is very strong, resilient, and iridescent....

    . In recent years however, the majority of "pearl buttons" are imitations that are made of pearlescent plastic.

In crafts

"Sailor's Valentines
Sailor's Valentines
A sailor's valentine is a type of antique souvenir, or sentimental gift, originally brought home from a sailor's voyage at sea for his loved one between 1830 and 1890...

" were late 19th century decorative keepsakes which were made in the Caribbean, and which were often purchased by sailors to give to their loved ones back home for example in England. These valentines consisted of elaborate arrangements of small seashells glued into attractive symmetrical designs, which were encased on a wooden (usually octagonal) hinged box-frame. The patterns used often featured heart-shaped designs, or included a sentimental expression of love spelled out in small shells.

The making of shellwork artifacts is a practice of Aboriginal women
Indigenous Australians
Indigenous Australians are the original inhabitants of the Australian continent and nearby islands. The Aboriginal Indigenous Australians migrated from the Indian continent around 75,000 to 100,000 years ago....

 from La Perouse
La Perouse, New South Wales
Lapérouse is a suburb in south-eastern Sydney, in the state of New South Wales, Australia. The suburb of Lapérouse is located about 14 kilometres south-east of the Sydney central business district, in the City of Randwick....

 in Sydney, New South Wales, dating back to the 19th century. Shellwork objects include baby shoes, jewelry boxes and replicas of famous landmarks, including the Sydney Harbour Bridge
Sydney Harbour Bridge
The Sydney Harbour Bridge is a steel through arch bridge across Sydney Harbour that carries rail, vehicular, bicycle and pedestrian traffic between the Sydney central business district and the North Shore. The dramatic view of the bridge, the harbour, and the nearby Sydney Opera House is an iconic...

 and the Sydney Opera House
Sydney Opera House
The Sydney Opera House is a multi-venue performing arts centre in the Australian city of Sydney. It was conceived and largely built by Danish architect Jørn Utzon, finally opening in 1973 after a long gestation starting with his competition-winning design in 1957...

. The shellwork tradition began as an Aboriginal women's craft which was adapted and tailored to suit the tourist souvenir market, and which is now considered high art.

In architectural decoration

Small pieces of colored and iridescent shell have been used to create mosaic
Mosaic
Mosaic is the art of creating images with an assemblage of small pieces of colored glass, stone, or other materials. It may be a technique of decorative art, an aspect of interior decoration, or of cultural and spiritual significance as in a cathedral...

s and inlay
Inlay
Inlay is a decorative technique of inserting pieces of contrasting, often coloured materials into depressions in a base object to form patterns or pictures that normally are flush with the matrix. In a wood matrix, inlays commonly use wood veneers, but other materials like shells, mother-of-pearl,...

s, which have been used to decorate walls, furniture and boxes. Large numbers of whole seashells, arranged to form patterns, have been used to decorate mirror frames, furniture and man-made grotto
Grotto
A grotto is any type of natural or artificial cave that is associated with modern, historic or prehistoric use by humans. When it is not an artificial garden feature, a grotto is often a small cave near water and often flooded or liable to flood at high tide...

s.

In art

The pleasing designs of seashells have caused them to be featured in art in various ways, in paintings, in sculpture, and so on. A very large outdoor sculpture at Akkulam
Akkulam
Akkulam is a neighborhood of Thiruvananthapuram city, the capital of Kerala state in India. It is about 10 km from Thiruvananthapuram city center. It is a well known for the picnic and backwater destination Akkulam Lake, an extension of Veli Lake, where it joins with the sea...

 of a gastropod seashell is a reference to the sacred chank shell Turbinella pyrum
Turbinella pyrum
Turbinella pyrum, common names the chank shell, sacred chank or chank, also known as the divine conch, sometimes referred to simply as a conch, is a species of very large sea snail with a gill and an operculum, a marine gastropod mollusk in the family Turbinellidae...

of India. Maggi Hambling
Maggi Hambling
Maggi Hambling CBE is an English painter and sculptor. Perhaps her best known public works are a memorial to Oscar Wilde in central London and Scallop, a 4 metre high steel sculpture of two interlocking scallop shells on Aldeburgh beach dedicated to Benjamin Britten...

 designed a striking 13 ft (4 m) high sculpture of a scallop
Scallop
A scallop is a marine bivalve mollusk of the family Pectinidae. Scallops are a cosmopolitan family, found in all of the world's oceans. Many scallops are highly prized as a food source...

 shell which stands on the beach at Aldeburgh
Aldeburgh
Aldeburgh is a coastal town in Suffolk, East Anglia, England. Located on the River Alde, the town is notable for its Blue Flag shingle beach and fisherman huts where freshly caught fish are sold daily, and the Aldeburgh Yacht Club...

, in England. The goddess of love, Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...

 or Aphrodite
Aphrodite
Aphrodite is the Greek goddess of love, beauty, pleasure, and procreation.Her Roman equivalent is the goddess .Historically, her cult in Greece was imported from, or influenced by, the cult of Astarte in Phoenicia....

 is often traditionally depicted rising from the sea on a seashell. In the Birth of Venus (Botticelli)
The Birth of Venus (Botticelli)
The Birth of Venus is a painting by Sandro Botticelli. It depicts the goddess Venus, having emerged from the sea as a fully grown woman, arriving at the sea-shore...

, Botticelli depicted the goddess Venus rising from the ocean on a scallop
Scallop
A scallop is a marine bivalve mollusk of the family Pectinidae. Scallops are a cosmopolitan family, found in all of the world's oceans. Many scallops are highly prized as a food source...

 shell.

As an additive to poultry feeds

Sea shells found in the creek and backwater of the coast of west India are used as an additive to poultry feed. They are crushed and mixed with jawar maaze and dry fish.

Arthropods

Many arthropod
Arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...

s have sclerite
Sclerite
A sclerite is a hardened body part. The term is used in various branches of biology for various structures including hardened portions of sponges, but it is most commonly used for the hardened portions of arthropod exoskeletons....

s, or hardened body parts, which form a stiff exoskeleton made up mostly of chitin
Chitin
Chitin n is a long-chain polymer of a N-acetylglucosamine, a derivative of glucose, and is found in many places throughout the natural world...

. In crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...

s, especially those of the class Malacostraca
Malacostraca
Malacostraca is the largest of the six classes of crustaceans, containing over 25,000 extant species, divided among 16 orders. Its members display a greater diversity of body forms than any other class of animals, and include crabs, lobsters, shrimp, krill, woodlice, scuds , mantis shrimp and many...

 (crabs, shrimps and lobsters, for instance), the plates of the exoskeleton may be fused to form a more or less rigid carapace
Carapace
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...

. Moulted carapaces of a variety of marine malacostraceans often wash up on beaches. The horseshoe crab
Horseshoe crab
The Atlantic horseshoe crab, Limulus polyphemus, is a marine chelicerate arthropod. Despite its name, it is more closely related to spiders, ticks, and scorpions than to crabs. Horseshoe crabs are most commonly found in the Gulf of Mexico and along the northern Atlantic coast of North America...

 is an arthropod of the family Limulidae
Limulidae
Horseshoe crabs are arthropods that live primarily in shallow ocean waters on soft sandy or muddy bottoms. They will occasionally come on shore for mating...

. The shells or exuviae of these arachnids are common in beach drift in certain areas of the world.

Sea urchins

Some echinoderm
Echinoderm
Echinoderms are a phylum of marine animals. Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone....

s such as sea urchin
Sea urchin
Sea urchins or urchins are small, spiny, globular animals which, with their close kin, such as sand dollars, constitute the class Echinoidea of the echinoderm phylum. They inhabit all oceans. Their shell, or "test", is round and spiny, typically from across. Common colors include black and dull...

s, including heart urchins and sand dollar
Sand dollar
The term Sand dollar refers to species of extremely flattened, burrowing echinoids belonging to the order Clypeasteroida. Some species within the order, not quite as flat, are known as sea biscuits...

s, have a hard "test" or shell. After the animal dies, the flesh rots out and the spines fall off, and then fairly often the empty test washes up whole onto a beach, where it can be found by a beachcomber. These tests are fragile and easily broken into pieces.

Brachiopods

The brachiopod
Brachiopod
Brachiopods are a phylum of marine animals that have hard "valves" on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, while the front can be opened for feeding or closed for protection...

s, or lamp shells, superficially resemble clams, but the phylum is completely unrelated to mollusks. Most lines of brachiopods ended during the Permian-Triassic extinction event
Permian-Triassic extinction event
The Permian–Triassic extinction event, informally known as the Great Dying, was an extinction event that occurred 252.28 Ma ago, forming the boundary between the Permian and Triassic geologic periods, as well as the Paleozoic and Mesozoic eras...

, and their ecological niche was filled by bivalves. A few of the remaining species of brachiopods occur in the low intertidal zone
Intertidal zone
The intertidal zone is the area that is above water at low tide and under water at high tide . This area can include many different types of habitats, with many types of animals like starfish, sea urchins, and some species of coral...

 and thus can be found live by beachcombers.

Annelids

Some polychaetes, marine annelid worms in the family Serpulidae
Serpulidae
Serpulidae is a family of sessile, tube-building annelid worms in the class Polychaeta. The members of this family differ from the sabellid tube worms in that they have a specialized operculum that blocks the entrance of their tubes when they withdraw into the tubes. In addition, serpulids secrete...

, secrete a hard tube made of calcium carbonate, adhering to stones or other shells. This tube resembles, and can be confused with, the shell of marine gastropod mollusks in the family Vermetidae
Vermetidae
Vermetidae, common name the worm snails or worm shells, is a taxonomic family of small to medium-sized sea snails, marine gastropod molluscs in the clade Littorinimorpha....

, the worm snails.

Other more atypical kinds

A few other categories of marine animals leave remains which might be considered "seashells" in the widest possible sense of the word.

Vertebrate "shells": chelonians

Sea turtle
Sea turtle
Sea turtles are marine reptiles that inhabit all of the world's oceans except the Arctic.-Distribution:...

s have a carapace
Carapace
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...

 and plastron of bone and cartilage
Cartilage
Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...

 which is developed from their rib
Rib
In vertebrate anatomy, ribs are the long curved bones which form the rib cage. In most vertebrates, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the chest cavity. They serve to protect the lungs, heart, and other internal organs of the thorax...

s. Infrequently a turtle "shell" will wash up on a beach.

Hard corals

Pieces of the hard skeleton of coral
Coral
Corals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.A coral "head" is a colony of...

s commonly wash up on beaches in areas where corals grow.

The construction of the shell-like structures of corals are aided by a symbiotic relationship with a class of algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

, zooxanthella
Zooxanthella
Zooxanthellae are flagellate protozoa that are golden-brown intracellular endosymbionts of various marine animals and protozoa, especially anthozoans such as the scleractinian corals and the tropical sea anemone, Aiptasia....

e. Typically a coral polyp will harbor particular species of algae, which will photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

e and thereby provide energy for the coral and aid in calcification, while living in a safe environment and using the carbon dioxide and nitrogenous waste produced by the polyp. Coral bleaching
Coral bleaching
Coral bleaching is the loss of intracellular endosymbionts through either expulsion or loss of algal pigmentation.The corals that form the structure of the great reef ecosystems of tropical seas depend upon a symbiotic relationship with unicellular flagellate protozoa, called zooxanthellae, that...

 is a disruption of the balance between polyps and algae, and can lead to the breakdown and death of coral reefs.

Soft corals

The skeletons of soft corals such as gorgonians, also known as sea fan
Sea fan
A gorgonian, also known as sea whip or sea fan, is an order of sessile colonial cnidarian found throughout the oceans of the world, especially in the tropics and subtropics. Gorgonians are similar to the sea pen, another soft coral. Individual tiny polyps form colonies that are normally erect,...

s and sea whips, commonly wash ashore in the tropics
Tropics
The tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately  N and the Tropic of Capricorn in the southern hemisphere at  S; these latitudes correspond to the axial tilt of the Earth...

 after storms.

Plankton and protists

Plant-like diatom
Diatom
Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...

s and animal-like radiolarian
Radiolarian
Radiolarians are amoeboid protozoa that produce intricate mineral skeletons, typically with a central capsule dividing the cell into inner and outer portions, called endoplasm and ectoplasm. They are found as zooplankton throughout the ocean, and their skeletal remains cover large portions of the...

s are two forms of plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...

 which form hard silicate shells. Foraminifera
Foraminifera
The Foraminifera , or forams for short, are a large group of amoeboid protists which are among the commonest plankton species. They have reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net...

 and coccolithophore
Coccolithophore
Coccolithophores are single-celled algae, protists, and phytoplankton belonging to the division of haptophytes. They are distinguished by special calcium carbonate plates of uncertain function called coccoliths , which are important microfossils...

 create shells known as "test
Test (biology)
A test is a term used to refer to the shell of sea urchins, and also the shell of certain microorganisms, such as testate foraminifera and testate amoebae....

s" which are made of calcium carbonate. All these shells and tests are usually (but in the case of foraminifera not always) microscopic in size.

See also

  • Bailey-Matthews Shell Museum
    Bailey-Matthews Shell Museum
    The Bailey-Matthews Shell Museum is a museum of seashells and conchology located in the city of Sanibel, Florida on Sanibel Island on the Gulf coast of Southwest Florida...

  • Gastropod shell
    Gastropod shell
    The gastropod shell is a shell which is part of the body of a gastropod or snail, one kind of mollusc. The gastropod shell is an external skeleton or exoskeleton, which serves not only for muscle attachment, but also for protection from predators and from mechanical damage...

  • Mollusk shell
  • Ocean acidification
    Ocean acidification
    Ocean acidification is the name given to the ongoing decrease in the pH and increase in acidity of the Earth's oceans, caused by the uptake of anthropogenic carbon dioxide from the atmosphere....

  • Seashell resonance
    Seashell resonance
    There is a popular folk myth that if one holds a seashell—specifically, most often, a conch shell—to one's ear, one can hear the sound of the ocean....

  • Seashell surface
    Seashell surface
    In mathematics, a seashell surface is a surface made by a circle which spirals up the z-axis while decreasing its own radius and distance from the z-axis...

    , a mathematical construct

Books

  • Abbott R. Tucker & S. Peter Dance, 1982, Compendium of Seashells, A full color guide to more than 4,200 of the World's Marine shells, E.P. Dutton, Inc, New York, ISBN 0-525-93269-0
  • Abbott R. Tucker, 1985, Seashells of the World: a guide to the better-known species, 1985, Golden Press, New York, ISBN 0-307-24410-5
  • Abbott, R. Tucker, 1986, Seashells of North America, St. Martin's Press, New York, ISBN 1-58238-125-9
  • Abbott, R. Tucker, 1974, American Seashells, Second edition, Van Nostrand Rheinhold, New York, ISBN 0-442-20228-8.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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