''Crepidula onyx'', the onyx slippersnail or onyx slipper snail, is a

species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

of sea snail with

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they ar ...

s, a

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

gastropod mollusc in the family

Calyptraeidae The Calyptraeidae are a family of small to medium-sized marine prosobranch gastropods. MolluscaBase. Calyptraeidae Lamarck, 1809. Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=141 ...

, the slipper snails and cup-and-saucer snails.

Shell description

The

shell Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses ** Thin-shell structure Science Biology * Seashell, a hard o ...

of ''Crepidula onyx'' is up to 70 mm in length. The interior of the shell is glossy and is a strong tan to dark brown color, similar to the common colors of the mineral

onyx Onyx primarily refers to the parallel banded variety of chalcedony, a silicate mineral. Agate and onyx are both varieties of layered chalcedony that differ only in the form of the bands: agate has curved bands and onyx has parallel bands. The c ...

. The "shelf" or "deck" is white. The shell of this species can be distinguished from the shell of ''

Crepidula adunca ''Crepidula adunca'', common name the "hooked slippersnail" is a species of sea snail or "slipper snail", a marine gastropod mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of wh ...

'' by: * Its larger size, * The

apex The apex is the highest point of something. The word may also refer to: Arts and media Fictional entities * Apex (comics), a teenaged super villainess in the Marvel Universe * Ape-X, a super-intelligent ape in the Squadron Supreme universe *Apex, ...

is low and near the margin of the shell, curved to one side and not markedly hooked (rather than high, hooked and centrally placed), * The interior shelf is notched at the ends, rather than curved forward at both ends, and * The

periostracum The periostracum ( ) is a thin, organic coating (or "skin") that is the outermost layer of the shell of many shelled animals, including molluscs and brachiopods. Among molluscs, it is primarily seen in snails and clams, i.e. in gastropods a ...

is more prominent.Morris, Robert H. 2002. Intertidal Invertebrates of California: 690

Distribution

The native range for this species is the Eastern

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contine ...

coast of the Americas, from

Southern California Southern California (commonly shortened to SoCal) is a geographic and cultural region that generally comprises the southern portion of the U.S. state of California. It includes the Los Angeles metropolitan area, the second most populous urban ...

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the eas ...

Nonindigenous distribution

The species has been introduced and is considered to be established in

Puget Sound Puget Sound ( ) is a sound of the Pacific Northwest, an inlet of the Pacific Ocean, and part of the Salish Sea. It is located along the northwestern coast of the U.S. state of Washington. It is a complex estuarine system of interconnected m ...

Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...

, since 2005.

Ecology

Habitat

This species is common on rocks, shells, and pilings in protected bays, but it also lives in sheltered places on the open coast, occurring from the low

intertidal zone The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various species ...

subtidal The neritic zone (or sublittoral zone) is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately in depth. From the point of view of marine biology it forms a relatively stable and well-illuminated ...

waters.

References

This article incorporates public domain text (a

public domain The public domain (PD) consists of all the creative work to which no exclusive intellectual property rights apply. Those rights may have expired, been forfeited, expressly waived, or may be inapplicable. Because those rights have expired, ...

work of the United States Government) from: * 2008. ''Crepidula onyx''.

USGS The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

Nonindigenous Aquatic Species Database, Gainesville, FL. . Calyptraeidae Gastropods described in 1824 Taxa named by George Brettingham Sowerby I {{Calyptraeidae-stub