View source for Seashell

{{short description|Hard, protective outer layers created by an animal that lives in the sea}}
{{distinguish|Seychelles}}
{{for-multi|the coaster ship|MV Seashell|the color|Seashell (color)}}
{{More citations needed|date=January 2009}}
{{Use dmy dates|date=September 2020}}
{{sea shell topics}}

[[File:Conchiglie Seashells 01.jpg|right|thumb|Seashells washed up on the beach in [[Valencia, Spain]]; nearly all are single valves of [[bivalve]] [[mollusk]]s, mostly of ''[[Mactra corallina]]'']]
[[File:Selection of seashells.jpg|right|thumb|Hand-picked molluscan seashells ([[bivalve]]s and [[gastropod]]s) from the beach at [[Clacton on Sea]] in England]]
[[File:Seashells.JPG|thumb|A group of seashells, mostly bivalves in the family Pholadidae]]
[[File:Seashell unknown 3.jpg|thumb|226x226px|Mixed shells on a beach in Venezuela]]
[[File:Seashells living in Persian Gulf.ogv|thumb|[[Hermit crab]]s inhabiting marine gastropod shells that lived in the [[Persian Gulf]]]]
[[File:Different types of shells.jpg|thumb|A group of beachworn sea snail shells that vary in size, form and pattern combination.]]

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. Most seashells are made by [[Mollusca|mollusks]], such as [[snail]]s, [[clam]]s, and [[oyster]]s to protect their soft insides.<ref name=":0">{{Cite web |title=How are seashells made? |url=https://www.whoi.edu/know-your-ocean/did-you-know/how-are-seashells-made/ |access-date=14 May 2024 |website=Woods Hole Oceanographic Institution |language=en-US |archive-date=22 March 2022 |archive-url=https://web.archive.org/web/20220322101724/https://www.whoi.edu/know-your-ocean/did-you-know/how-are-seashells-made/ |url-status=live }}</ref> Empty seashells are often found washed up on [[beach]]es by [[beachcombing|beachcombers]]. The shells are empty because the animal has died and the soft parts have [[decomposition|decomposed]] or been eaten by another organism.

A seashell is usually the [[exoskeleton]] of an [[invertebrate]] (an animal without a backbone), and is typically composed of [[calcium carbonate]]<ref name=":0" /> or [[chitin]]. Most shells that are found on beaches are the shells of [[marine (ocean)|marine]] mollusks, partly because these shells are usually made of calcium carbonate, and endure better than shells made of chitin.

Apart from [[mollusk shell]]s, other shells that can be found on beaches are those of [[barnacle]]s, [[horseshoe crab]]s and [[brachiopod]]s. Marine [[annelid]] worms in the family [[Serpulidae]] create shells which are tubes made of calcium carbonate cemented onto other surfaces. The shells of [[sea urchin]]s are called "[[test (zoology)|test]]s", and the moulted shells of [[crab]]s and [[lobster]]s are [[exuviae]]. While most seashells are external, some [[cephalopods]] have internal shells.

Seashells have been used by humans for many different purposes throughout history and prehistory. However, seashells are not the only kind of shells; in various habitats, there are shells from freshwater animals such as [[freshwater mussel]]s and [[freshwater snail]]s, and shells of [[land snail]]s.

== Terminology ==
When the word "seashells" refers only to the shells of marine mollusks, then studying seashells is part of [[conchology]]. 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.

The study of mollusks (including their shells) is known as [[malacology]]; a person who studies mollusks is known as a [[malacologist]].

== Occurrence ==
Seashells are commonly found in beach drift, which is natural detritus deposited along strandlines on [[beach]]es by the [[wave]]s and the [[tide]]s. Shells are very often washed up onto a beach empty and clean, the animal having already died.

Empty seashells are often picked up by beachcombers. 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.<ref>{{Cite web|url=https://www.nationalgeographic.com/animals/2018/07/wildlife-watch-seashells-illegal-trade-handicrafts/|archive-url=https://web.archive.org/web/20180716171356/https://www.nationalgeographic.com/animals/2018/07/wildlife-watch-seashells-illegal-trade-handicrafts/|url-status=dead|archive-date=16 July 2018|title=Seashell Souvenirs Are Killing Protected Marine Life|date=16 July 2018|website=Animals|access-date=19 March 2019}}</ref> This type of large-scale exploitation can sometimes have a strong negative impact on local [[ecosystem]]s, and sometimes can significantly reduce the distribution of [[rare species]].

== Shell synthesis ==
Seashells are created by the [[Mollusca|mollusc]]s that use them for protection.<ref name="whoi">{{Cite web |title=How are seashells made? |url=https://www.whoi.edu/know-your-ocean/did-you-know/how-are-seashells-made/ |publisher=Woods Hole Oceanographic Institution |date=2022 |accessdate=21 March 2022 |archive-date=20 March 2022 |archive-url=https://web.archive.org/web/20220320212038/https://www.whoi.edu/know-your-ocean/did-you-know/how-are-seashells-made/ |url-status=live }}</ref> Molluscs have an outside layer of tissues on their bodies {{ndash}} the [[mantle (mollusc)|mantle]] {{ndash}} which creates the shell material and which connects the shell to the mollusc. The specialized cells in the mantle form the shell using different [[Mineral (nutrient)|minerals]] and [[protein]]s.<ref name=whoi/> The proteins are then used to create the framework that supports the growing shell. [[Calcium carbonate]] is the main compound of shell structure, aiding in [[adhesion]].<ref name=whoi/>

== Molluscan seashells ==
{{more citations needed section|date=September 2011}}

[[File:Seashells North Wales 1985.jpg|thumb|Seashells hand-picked from beach drift in [[North Wales]] at [[Shell Island (Wales)|Shell Island]] near [[Harlech Castle]], [[Wales]], [[bivalve]]s and [[gastropod]]s, March/April 1985]]
{{main|Mollusc shell}}
[[File:Shells on the seashore.jpg|thumb|Shells on the seashore]]

The word ''seashell'' is often used to mean only the shell of a [[Marine (ocean)|marine]] [[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]]s), [[gastropod]]s (or [[snail]]s), [[scaphopod]]s (or [[tusk shell]]s), [[polyplacophora]]ns (or [[chiton]]s), and [[cephalopod]]s (such as [[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 (mollusc)|sculpture]] 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]]s.

Not all mollusks are marine. There are numerous land and freshwater mollusks, see for example [[snail]] and [[freshwater bivalves]]. In addition, 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]] and [[nudibranch]].

=== Bivalves ===
{{main|Bivalvia}}
[[File:CoquillagesFadiouth.jpg|thumb|Single valves of the [[bivalve]] ''[[Senilia senilis]]'', plus two [[gastropod]]s, washed up on the beach at [[Fadiouth]], [[Senegal]]]]
Bivalves are often the most common seashells that wash up on large sandy beaches or in sheltered [[lagoon]]s. They can sometimes be extremely numerous. Very often the two [[valve (mollusc)|valves]] become separated.

There are more than 15,000 species of bivalves that live in both marine and freshwater.  Examples of bivalves are clams, scallops, mussels, and oysters. The majority of bivalves consist of two identical shells that are held together by a flexible hinge.  The animal's body is held protectively inside these two shells. Bivalves that do not have two shells either have one shell or they lack a shell altogether. The shells are made of calcium carbonate and are formed in layers by secretions from the mantle. Bivalves, also known as pelecypods, are mostly filter feeders; through their gills, they draw in water, in which is trapped tiny food particles.  Some bivalves have eyes and an open circulatory system.  Bivalves are used all over the world as food and as a source of pearls. The larvae of some freshwater mussels can be dangerous to fish and can bore through wood.

[[Shell Beach, Western Australia]], is a beach which is entirely made up of the shells of the [[cockle (bivalve)|cockle]] ''[[Fragum erugatum]]''.

=== Gastropods ===
{{main|Gastropod shell}}
[[File:Sea shells, playa grande, costa rica.jpg|thumb|Numerous ''[[Turritella]]'' gastropod shells washed up on a beach at [[Playa Grande, Costa Rica]]]]
Certain species of gastropod seashells (the shells of [[sea snail]]s) can sometimes be common, washed up on sandy beaches, and also on beaches that are surrounded by rocky marine habitat.

=== Polyplacophorans ===
{{main|Chiton}}
[[File:Chiton tuberculatus plates.jpg|thumb|130px|left|Loose valves or plates from ''[[Chiton tuberculatus]]'' from the beachdrift on the southeast coast of [[Nevis]], [[West Indies]]]]
[[Chiton]] 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 ===
{{main|Cephalopod}}
[[File:Cuttlebone.jpg|thumb|130px|Cuttlebone from a ''[[Sepia (genus)|Sepia]]'' sp.]]
[[File:Nautilus species shells.png|thumb|130px|Shells of 3 species of ''[[Nautilus]]'']]

Only a few species of [[cephalopod]]s have shells (either internal or external) that are sometimes found washed up on beaches.

Some cephalopods such as ''[[Sepia (genus)|Sepia]]'', 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&nbsp;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]]'' is the only genus of cephalopod that has a well-developed external shell. Females of the cephalopod genus ''[[Argonaut (animal)|Argonauta]]'' 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]]s, are extinct, but their shells are very common in certain areas as [[fossil]]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]], and in the shallow subtidal zone.  As such they are sometimes used [[second-hand]] by animals other than humans for various purposes, including for protection (as in [[hermit crab]]s) and for construction.

==== Mollusks ====
* Carrier shells in the family [[Xenophoridae]] 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 (biology)|substrate]] where the snail itself lives. It is not clear whether these shell attachments serve as [[camouflage]], or whether they are intended to help prevent the shell sinking into a soft substrate.

[[File:Ocellated octopus.jpg|thumb|left|An ocellated (spotted) octopus using a clamshell as a shelter]]
* Small [[octopus]]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.

==== Invertebrates ====
[[File:Diogenes pugilator.jpg|thumb|Marine [[hermit crab]] ''[[Diogenes pugilator]]'', using a shell of the dog whelk ''[[Nassarius reticulatus]]'']]
{{biomineralization sidebar|exoskeletons}}

* Almost all genera of [[hermit crab]]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]]''.

=== Conchology ===
{{main|Conchology}}

There are numerous popular books and [[field guide]]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]]. 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]]. 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]]: 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]] 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 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]].

==== 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 US, these clubs are more common in southerly coastal areas, such as [[Florida]] and [[California]], where the marine fauna is rich in species.

==== Identification ====
[[File:Concha com pintura (1.2), Acervo do Museu do Colono (Santa Leopoldina).jpg|thumb|A [[Conch shell]], often [[Conch (instrument)|used as a musical instrument]]]]
Seashells are usually identified by consulting general or regional shell-collecting [[field guide]]s, and specific scientific books on different taxa of shell-bearing mollusks ([[monograph]]s) or "iconographies" (limited text – mainly photographs or other illustrations). (For a few titles on this subject in the US, 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]]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]]) 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]] (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" ====
[[File:Shells01.jpg|thumb|A group of purchased (mostly marine) shells includes the shell of a large tropical land snail (upper right), and a shiny freshwater apple snail shell (center)]]

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 mollusc|freshwater mollusk]] 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 [[snail|land snail]] 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.

=== Cultural significance ===
{{further|Molluscs in culture}}
{{more citations needed section|date=July 2016}}

==== Currency ====
{{main|shell money}}

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.
[[Image:Cypraea-moneta-001.jpg|thumb|1742 drawing of shells of the money cowry, ''[[Monetaria moneta]]'']]
* The most common species of shells to be used as currency have been ''[[Monetaria moneta]]'', the "money [[cowry]]",<ref name="Poutiers">{{cite book|last=Poutiers|first=J. M.|date=1998|chapter=Gastropods|url=http://www.fao.org/docrep/009/w7191e/w7191e44.pdf|title=FAO Species Identification Guide for Fishery Purposes: The living marine resources of the Western Central Pacific|volume=1. Seaweeds, corals, bivalves and gastropods|location=Rome|publisher=FAO|page=503|access-date=30 January 2019|archive-date=31 January 2019|archive-url=https://web.archive.org/web/20190131043502/http://www.fao.org/docrep/009/w7191e/w7191e44.pdf|url-status=live}}</ref><ref>Hogendorn, Jan and Johnson Marion: The Shell Money of the Slave Trade. African Studies Series 49, [[Cambridge University Press]], [[Cambridge]], 1986.</ref> and certain [[Dentalium (anthropology)|dentalium]] [[tusk shell]]s, used in North Western North America for many centuries.
* Many of the tribes and nations all across the continent of Africa have historically used the [https://web.archive.org/web/20160323070635/http://www.blackhistorypages.net/pages/cowrie.php cowry] as their media of exchange. The cowry circulated, historically, alongside metal coins and goods, and foreign currencies. Being durable and easy to carry the cowry made a very favorable currency.
* Some tribes of the [[indigenous peoples of the Americas]] used shells for [[wampum]] and [[hair pipe]]s.<ref>[[John C. Ewers|Ewers, John C.]] "[http://www.sil.si.edu/DigitalCollections/BAE/Bulletin164/section2.htm#Shell%20hp Hair Pipes in Plains Indian Adornment] {{Webarchive|url=https://web.archive.org/web/20071201173655/http://www.sil.si.edu/DigitalCollections/BAE/Bulletin164/section2.htm#Shell%20hp |date=1 December 2007 }}", ''Bureau of American Ethnology Bulletin 164'', pp. 29–85.  United States Government Printing Office, Washington : 1957.</ref> The Native American ''[[wampum]] belts'' were made of the shell of the [[quahog]] clam.

==== Tools ====
Seashells have often been used as [[tool]]s, because of their strength and the variety of their shapes.
* [[Giant clam]]s (Family Tridacnidae) have been used as bowls, and when big enough, even as bathtubs and [[baptism]]al fonts.
* ''[[Melo melo]]'', the "bailer [[Volutidae|volute]]", is so named because Native Australians used it to [[Bailing (boats)|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]]s, the oil being poured in the aperture of the shell, and the [[siphonal canal]] serving as a holder for the wick.

==== Horticulture ====
Because seashells are in some areas a readily available bulk source of calcium carbonate, shells such as [[oyster]] shells are sometimes used as soil conditioners in [[horticulture]]. The shells are broken or ground into small pieces in order to have the desired effect of raising the [[pH]] and increasing the [[calcium]] content in the soil.

==== Religion and spirituality ====
[[File:Flag of Kingdom of Travancore.svg|thumb|A sacred chank shell on the flag of [[Travancore]], India]]
<!-- Deleted image removed: [[File:Strombuslarcomuseum.jpg|thumb|right|Moche Shell, 200 A.D. [[Larco Museum|Larco Museum Collection]] Lima, Peru.]] -->
[[File:Spatha shell. From Naqada tomb 1539, Egypt. Naqada I period. The Petrie Museum of Egyptian Archaeology, London.jpg|thumb|Spatha shell. From Naqada tomb 1539, Egypt. Naqada I period. The Petrie Museum of Egyptian Archaeology, London]]
Seashells have played a part in religion and spirituality, sometimes even as ritual objects.
* In Christianity, the [[scallop]] shell is considered to be the symbol of [[Saint James the Great]], see ''[[Pecten jacobaeus]]''.<ref>{{Cite web|last=Raichlen|first=Steven|title=The venerable scallop's versatility makes it a rare culinary blessing|url=https://www.baltimoresun.com/news/bs-xpm-1990-11-04-1990308108-story.html|access-date=12 November 2020|website=baltimoresun.com|date=4 November 1990|language=en-US|archive-date=8 May 2021|archive-url=https://web.archive.org/web/20210508232021/https://www.baltimoresun.com/news/bs-xpm-1990-11-04-1990308108-story.html|url-status=live}}</ref>
* In [[Hinduism]], left-handed shells of ''[[Turbinella pyrum]]'' (the sacred [[shankha]]) are considered to be sacred to the god [[Vishnu]]. 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]].
* [[Cowries]] have often been considered to be symbols of female fertility. They were often treated as actual fertility [[amulet|charms]]. The dorsum of the shell resembles a pregnant belly, and the underside of the shell resembles a [[vulva]]. In the South Indian state of Kerala, cowries are used for making astrological predictions.
* In the [[Santería]] religion, shells are used for [[divination]].
* The [[Moche (culture)|Moche]] culture of ancient [[Peru]] worshipped animals and the sea, and often depicted shells in their art.<ref>Berrin, Katherine & Larco Museum. ''The Spirit of Ancient Peru:Treasures from the [[Larco Museum|Museo Arqueológico Rafael Larco Herrera]].'' New York: [[Thames and Hudson]], 1997.</ref>
* In Christianity, the top of the [[sand dollar]] represents the Star of Bethlehem that led the Wise Men to the manger of Christ. Outside the "star" you will see the Easter Lily, a sign of Jesus' Resurrection. There are four holes that represent the holes in the Lord's hands and feet. The center hole is the Wound to His Sacred Heart by the spear of Longinus. On the other side of the sand dollar, you will see Poinsettia. Lastly, if you break open the sand dollar, five doves will come out, the doves of Peace and Joy.<ref>The Legend of the Sand Dollar</ref>

==== Musical instruments ====
{{main|Conch (musical instrument)}}
[[File:Hindu priest blowing conch during punja.jpg|thumb|Hindu priest sounding a ritual trumpet made from ''[[Turbinella pyrum]]'']]
[[File:Gyeonbokgung-March-01.jpg|thumb|Korean military procession with ''[[Charonia]]'' trumpets]]

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 (mollusc)|spire]] 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]]" trumpets are:
* The sacred chank, ''[[Turbinella pyrum]]'', known in India as the [[shankha]]. In [[Tibet]] it is known as "dung-dkar".<ref name=Clark>{{cite web |url=http://www.furious.com/perfect/shells.html |title=Some Basics on Shell Trumpets and some very Basics on how to make them |author=Clark, Mitchell |year=1996 |publisher=furious.com |access-date=24 July 2016 |url-status=live |archive-url=https://web.archive.org/web/20131021010404/http://www.furious.com/perfect/shells.html |archive-date=21 October 2013}}</ref>
* The [[Triton (mollusk)|Triton shell]] also known as "Triton's trumpet" ''[[Charonia tritonis]]'' which is used as a trumpet in Melanesian and Polynesian culture and also in [[Korea]] and Japan. In Japan this kind of trumpet is known as the [[horagai]]. In Korea it is known as the [[nagak]]. In some Polynesian islands it is known as "''pu''".<ref name=Clark/>
* The [[Queen Conch]] ''[[Lobatus gigas]]'', has been used as a trumpet in the Caribbean.

Children in some cultures are often told the myth that you can hear the sound of the ocean by holding a seashell to ones ear. This is due to the effect of [[seashell resonance]].

==== Personal adornment ====
[[File:Kikuyu woman traditional dress.jpg|thumb|upright|Use of [[gastropod shell]]s, specifically [[cowries]], in traditional dress of the [[Kikuyu people]] of [[Kenya]], Africa]]
[[File:Pearlykingandqueen.jpg|right|thumb|upright|A [[Pearly Kings and Queens|Pearly King and Queen]] in London]]
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]].
* Shell necklaces have been found in Stone Age graves as far inland as the [[Dordogne]] Valley in France.
* Seashells are often used whole and drilled, so that they can be threaded like [[bead]]s, or cut into pieces of various shapes. Sometimes shells can be found that are already "drilled" by predatory snails of the family [[Naticidae]]. 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 [[Tasmanian Aboriginal|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.<ref>[http://www.nma.gov.au/collections/dulcie_greeno_necklaces Tasmanian Aboriginal shell necklaces] {{webarchive|url=https://web.archive.org/web/20110612010907/http://www.nma.gov.au/collections/dulcie_greeno_necklaces/ |date=12 June 2011 }}, [[National Museum of Australia]].</ref>
* 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]] these natural beads were traditionally collected from the beach drift in order to make [[puka shell]] 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 (clothing)|buttons]], [[brooch]]es, [[ring (finger)|rings]], [[comb|hair combs]], belt buckles and other uses.
* The shell of the large  "bullmouth helmet" sea snail, scientific name ''[[Cypraecassis rufa]]'', was historically, and still is, used to make valuable [[Cameo (carving)|cameos]].
* [[Nacre|Mother of pearl]] from many seashells including species in the family [[Trochidae]], [[Turbinidae]], [[Haliotidae]], and various pearly bivalves, has often been used in jewelry, buttons, etc.
* In London, [[Pearly Kings and Queens]] traditionally wear clothing covered in patterns made up of hundreds of "pearl [[Button (clothing)|buttons]]", in other words, buttons made of [[mother-of-pearl]] or [[nacre]]. In recent years however, the majority of "pearl buttons" are imitations that are made of pearlescent plastic.

==== Folk art ====
{{main|Shellcraft}}

"[[Sailor's valentine]]s" 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.<ref>{{Cite web |last=Bingham |first=Claire |date=2024-02-14 |title=Sailor's Valentines to warm the cockles of your heart |url=https://www.worldofinteriors.com/story/sailors-valentines |access-date=2025-11-07 |website=The World Of Interiors |language=en-GB}}</ref> 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 shell work artifacts is a practice of [[Indigenous Australians|Aboriginal women]] from [[La Perouse, New South Wales|La Perouse]] in [[Sydney]], dating back to the 19th century. Shell work objects include baby shoes, jewelry boxes and replicas of famous landmarks, including the [[Sydney Harbour Bridge]] and the [[Sydney Opera House]]. 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.<ref>{{cite web|url=https://www.nma.gov.au/explore/collection/highlights/shellwork-sydney-harbour-bridge |title = Shellwork Sydney Harbour Bridge|website= National Museum of Australia Collections|url-status = live|archive-url=https://web.archive.org/web/20190130215018/https://www.nma.gov.au/explore/collection/highlights/shellwork-sydney-harbour-bridge |archive-date=30 January 2019 }}</ref>

==== Architectural decoration ====
Small pieces of colored and iridescent shell have been used to create [[mosaic]]s and [[inlay]]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 human-made [[shell grotto]]s.

==== Art ====
[[File:Aphrodite Anadyomene Louvre CA2288.jpg|thumb|upright|[[Aphrodite]], 1st century BC, 13&nbsp;cm, 5&nbsp;in]]
A very large outdoor sculpture at [[Akkulam]] of a gastropod seashell is a reference to the sacred chank shell ''[[Turbinella pyrum]]'' of India. In 2003, [[Maggi Hambling]] designed a striking 13&nbsp;ft (4 m) high sculpture of a [[scallop]] shell which stands on the beach at [[Aldeburgh]], in England. The goddess of love, [[Venus (mythology)|Venus]] or [[Aphrodite]], is often traditionally depicted rising from the sea on a seashell.  In ''[[The Birth of Venus (Botticelli)|The Birth of Venus]]'', [[Botticelli]] depicted the goddess [[Venus (goddess)|Venus]] rising from the ocean on a [[scallop]] shell.

<gallery>
File:Akkulam shanku.jpg|Enormous seashell sculpture at [[Akkulam]], [[Thiruvananthapuram]], India
File:The Scallop, Maggi Hambling, Aldeburgh.jpg|Large sculpture of a [[scallop]] on the beach at [[Aldeburgh]], by [[Maggi Hambling]], 2003
File:Albertus Seba Muscheln.jpg|Illustration from an 18th-century book, edited by [[Albertus Seba]]. These decorative arrangements were a popular way to display seashells at the time
File:Hendrick Goltzius - Portrait of the Haarlem Shell Collector Jan Govertsen van der Aer - Google Art Project.jpg|Portrait of the Shell Collector Jan Govertsen van der Aer, by [[Hendrick Goltzius]] (1603)
</gallery>

==== 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 jowar maize and dry fish.{{Citation needed|date=February 2011}}

=== Use ===
Seashells, namely from bivalves<ref>{{Cite journal|last1=Ferraz|first1=Eduardo|last2=Gamelas|first2=José A. F.|last3=Coroado|first3=João|last4=Monteiro|first4=Carlos|last5=Rocha|first5=Fernando|date=12 July 2019|title=Recycling Waste Seashells to Produce Calcitic Lime: Characterization and Wet Slaking Reactivity|journal=Waste and Biomass Valorization|language=en|volume=10|issue=8 |pages=2397–2414|doi=10.1007/s12649-018-0232-y|bibcode=2019WBioV..10.2397F |issn=1877-2641}}</ref> and gastropods, are fundamentally composed of calcium carbonate. In this sense, they have potential to be used as raw material in the production of [[Lime (material)|lime]].

{{anchor|shellcrete}} Along the [[Gulf Coast of the United States]], [[oyster]] shells were mixed into [[cement]] to make "shellcrete" which could form bricks, blocks and platforms. It could also be applied over logs.<ref>{{cite book|title=Preservation News|url=https://books.google.com/books?id=_aYaAQAAMAAJ|year=1985|publisher=National Trust for Historic Preservation in the United States.|page=94|quote= Brittle buildings made of "shellcrete," a seashell-cement mix applied over logs, are risky to move.}}</ref> A notable example is the 19th-century [[Sabine Pass Lighthouse]] in Louisiana, near Texas.<ref>{{cite book|last=Tunnell|first=John Wesley|title=Encyclopedia of Texas Seashells|url=https://books.google.com/books?id=PIkC-rU2NkoC&pg=PA17|year=2010|publisher=Texas A&M U. Press|isbn=978-1-60344-337-1|pages=17–19|quote= Many impressive old homes and public buildings, as well as more mundane structures such as cisterns and curbs, were constructed of shellcrete bricks in Corpus Christi, Galveston, and other cities along the coast. However, very few exist today.}}</ref>

== Shells of other marine invertebrates ==
{{Unreferenced section|date=December 2017}}

=== Arthropods ===
[[File:Crab from Long Island.jpg|thumb|The moulted [[carapace]] of a [[lady crab]] found on the beach at [[Long Beach, New York|Long Beach, Long Island, New York State]]]]
[[File:Horseshoe Crab remains.jpg|thumb|left|Shell of [[horseshoe crab]] on a beach]]

Many [[arthropod]]s have [[sclerite]]s, or hardened body parts, which form a stiff exoskeleton made up mostly of [[chitin]].  In [[crustacean]]s, especially those of the class [[Malacostraca]] (crabs, shrimps and lobsters, for instance), the plates of the exoskeleton may be fused to form a more or less rigid [[carapace]]. Moulted carapaces of a variety of marine malacostraceans often wash up on beaches. The [[horseshoe crab]] is an arthropod of the family [[Limulidae]]. The shells or [[exuviae]] of these arachnid relatives are common in beach drift in certain areas of the world.

=== Echinoderms ===
[[File:Sea Urchin test 5629 03 22.jpg|thumb|[[Sea urchin]] test]]
Some [[echinoderm]]s such as [[sea urchin]]s, including [[heart urchin]]s and [[sand dollar]]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 ===
[[File:LingulaanatinaAA.JPG|thumb|A whole animal of the brachiopod ''[[Lingula anatina]]'' from Australia with the shell showing on the left]]
The [[brachiopod]]s, or lamp shells, superficially resemble clams, but the phylum is not closely related to mollusks. Most lines of brachiopods ended during the [[Permian-Triassic extinction event]], and their ecological niche was filled by bivalves. A few of the remaining species of brachiopods occur in the low [[intertidal zone]] and thus can be found live by beachcombers.

=== Annelids ===
Some [[polychaetes]], marine annelid worms in the family [[Serpulidae]], 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]], the worm snails.

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

=== Chelonians ===
[[Sea turtle]]s have a [[carapace]] and [[plastron]] of bone and [[cartilage]] which is developed from their [[rib]]s. Infrequently a turtle "shell" will wash up on a beach.

=== Hard corals ===
[[Image:Shells stones and other curios.JPG|thumb|Dish with beachworn coral pieces, marine gastropod shells, and echinoderm tests, from the Caribbean and the Mediterranean]]

Pieces of the hard skeleton of [[coral]]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]], [[zooxanthella]]e. Typically a coral polyp will harbor particular species of algae, which will [[photosynthesis]]e and thereby provide energy for the coral and aid in calcification,<ref name=MilneBay>
{{cite web
 |author1       = Madl, P.
 |author2       = Yip, M.
 |name-list-style = amp
 |year          = 2000
 |url           = http://biophysics.sbg.ac.at/png/png3.htm
 |work = Field Excursion to Milne Bay Province – Papua New Guinea Working Group: Scleractinian Corals (incl. Porifera)
|title=        PART-III Cnidaria (Gk. cnidos, stinging nettle) reproduction and growth of Scleractinia
|publisher=biophysics.sbg.ac.at
 |access-date    = 31 March 2006
 |url-status       = dead
 |archive-url    = https://web.archive.org/web/20120128205517/http://biophysics.sbg.ac.at/png/png3.htm
 |archive-date   = 28 January 2012}}</ref> while living in a safe environment and using the carbon dioxide and nitrogenous waste produced by the polyp.  [[Coral bleaching]] is a disruption of the balance between polyps and algae, and can lead to the breakdown and death of coral reefs.

=== Soft corals ===
[[File:1-Gorgone.jpg|thumb|An x-ray photograph of a [[gorgonian]]]]
The skeletons of soft corals such as [[gorgonian]]s, also known as [[sea fan]]s and [[sea whip]]s, commonly wash ashore in the [[tropics]] after storms.

=== Plankton and protists ===
{{further|Protist shells}}
[[File:Diatoms through the microscope.jpg|thumb|Marine [[diatom]]s form hard silicate shells]]

Plant-like [[diatom]]s and animal-like [[radiolarian]]s are two forms of [[plankton]] which form hard [[silica]]te shells. [[Foraminifera]] and [[coccolithophore]]s create shells known as "[[test (biology)|tests]]" which are made of calcium carbonate. These shells and tests are usually microscopic in size, though in the case of foraminifera, they are sometimes visible to the naked eye, often resembling miniature mollusk shells.

== See also ==
* [[Bailey-Matthews Shell Museum]]
* [[Marine biogenic calcification]]
* [[Mollusk shell]]
* [[Ocean acidification]]
* [[Seashell resonance]]
* [[Seashell surface]], a mathematical construct
* [[Shell growth in estuaries]]
* [[Shell purse]]
* [[Small shelly fauna]]

== References ==
=== Citations ===
{{Reflist}}

=== Sources ===
{{refbegin}}
; 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}}.
{{refend}}

== External links ==
{{Wiktionary|seashell}}{{commons category|Seashells}}
{{wikiquote}}
* [https://research.fit.edu/shells/ Hohlman Shell Collection, Florida Institute of Technology]
* ''[https://www.gutenberg.org/ebooks/74207 Beautiful Shells]'' (1856) by [[Henry Gardiner Adams|H. G. Adams]]

[[Category:Zoology]]
[[Category:Mollusc shells]]
[[Category:Mollusc products]]
[[Category:Collecting]]
[[Category:Articles containing video clips]]