The Cassidae are a

taxonomic Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. A ...

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

of medium-sized, large, and sometimes very large sea snails commonly called helmet snails or bonnet snails. These are

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

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is es ...

s in the superfamily

Tonnoidea The Tonnoidea are a superfamily of sea snails, marine gastropod molluscs in the order Littorinimorpha. This superfamily includes many very large species. Nomenclature Beu (1998, 2008) favours usage of Tonnoidea and Tonnidae rather than Ca ...

and the clade

Littorinimorpha Littorinimorpha is a large order of snails, gastropods, consisting primarily of sea snails ( marine species), but also including some freshwater snails ( aquatic species) and land snails ( terrestrial species).Bouchet P. & Rocroi J.-P. (Ed.); Fr ...

.Gofas, S. (2010). Cassidae. In: Bouchet, P.; Gofas, S.; Rosenberg, G. (2010) World Marine Mollusca database. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=22999 on 2011-01-19 About 60 species comprise the family Cassidae; an example is ''

Cypraecassis rufa ''Cypraecassis rufa'' is a species of large sea snail, a marine gastropod mollusc in the family Cassidae. It is commonly known as the bullmouth shell or red helmet shell, and also as the cameo shell. Distribution This species is found off ...

''.

Nomenclature

Despite its incorrect formation (the correct one would be Cassididae, based on the genitive form of Cassis), the ICZN has placed the name Cassidae Latreille, 1825 on the official list of family names, therefore avoiding homonymy with Cassididae Stephens, 1831 (based on Cassida Linnaeus, 1758, a chrysomelid beetle); Opinion 1023 (1974, Bulletin of Zoological Nomenclature 31: 127-129).

Distribution

Species of this family occur in tropical and temperate seas from the

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 ...

to depths of 100 m (330 ft), buried in the sand during the day and becoming active at night.

Shell description

Members of this family are shaped rather like bonnets or helmets, as their common name suggests. The shells are large, thick, subglobular with dextrally coiled, sometimes varicose, whorls, and a short

spire A spire is a tall, slender, pointed structure on top of a roof of a building or tower, especially at the summit of church steeples. A spire may have a square, circular, or polygonal plan, with a roughly conical or pyramidal shape. Spires are ...

. The coiling may be trochospiral or convoluted. The shells of many species have great variability, which has led to many misidentifications, resulting in many synonyms. Many species have a large and solid shield over the parietal body or beside the thick, plicated

columella Lucius Junius Moderatus Columella (; Arabic: , 4 – ) was a prominent writer on agriculture in the Roman Empire. His ' in twelve volumes has been completely preserved and forms an important source on Roman agriculture, together with the ...

. Many species show blunt knobs and thickened axial ridges, known as

varices A varix (pl. varices) is an abnormally dilated vessel with a tortuous course. Varices usually occur in the venous system, but may also occur in arterial or lymphatic vessels. Examples of varices include: * Varicose veins, large tortuous veins usua ...

. The thin, horny operculum is oval in shape and covers a long

aperture In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. An ...

. The

siphonal canal The siphonal canal is an anatomical feature of the shells of certain groups of sea snails within the clade Neogastropoda. Some sea marine gastropods have a soft tubular anterior extension of the mantle called a siphon through which water ...

is straight or slightly curved. The outer lip is somewhat thicker at its margin and toothed on the inside.

Anatomy

These snails have a large mantle and a large, muscular foot. Their large head has an extensible snout. The eyes are at the base of the single pair of tentacles.

Feeding habits

Helmet bonnets prey on

echinoderms An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the ...

(especially

sea urchin Sea urchins () are spiny, globular echinoderms in the class Echinoidea. About 950 species of sea urchin live on the seabed of every ocean and inhabit every depth zone from the intertidal seashore down to . The spherical, hard shells (tests) ...

s), starting by gripping them using the foot. The snail then makes a hole in the urchin through the combined action of a secretion which is rich in sulfuric acid and by rasping with their

radula The radula (, ; plural radulae or radulas) is an anatomical structure used by molluscs for feeding, sometimes compared to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food ...

. The acid secretion is provided by two large

proboscis A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular mouthparts used for feeding and sucking. In vertebrates, a proboscis is an elonga ...

glands.

Taxonomy

In their taxonomy of the Gastropoda of 2005 Bouchet & Rocroi still listed Cassidae as Cassinae Latreille, 1825, a subfamily of

Tonnidae The Tonnidae are a family of medium-sized to very large sea snails, known as the tun shells. These are marine gastropod molluscs in the clade Littorinimorpha. The name ''tun'' refers to the snails' shell shape, which resembles wine casks know ...

Suter, 1913 (1825), following in this Riedel (1995). In his "Revision of the deep-water Cassidae" however, Beu raised in 2008 Cassinae to the rank of family.Beu A.G. (2008) Recent deep-water Cassidae of the world. A revision of Galeodea, Oocorys, Sconsia, Echinophoria and related taxa, with new genera and species (Mollusca, Gastropoda). In Héros V., Cowie R.H. & Bouchet P. (eds), Tropical Deep-Sea Benthos 25. Mémoires du Muséum National d'Histoire Naturelle 196: 269-387.

Genera

Genera within the family include: *'' Casmaria'' H. Adams and A. Adams, 1853 *''

Cassis Cassis (; Occitan: ''Cassís'') is a commune situated east of Marseille in the department of Bouches-du-Rhône in the Provence-Alpes-Côte d'Azur region, whose coastline is known in English as the French Riviera, in Southern France. In 2016, ...

Scopoli Giovanni Antonio Scopoli (sometimes Latinized as Johannes Antonius Scopolius) (3 June 1723 – 8 May 1788) was an Italian physician and naturalist. His biographer Otto Guglia named him the "first anational European" and the "Linnaeus of the Au ...

, 1777 *'' Cypraecassis'' Stutchbury, 1837 *'' Dalium'' Dall, 1889 *''

Echinophoria ''Echinophoria'' is a genus of large sea snails, marine gastropod mollusks in the family Cassidae, the helmet snails and bonnet snails.Bouchet, P. (2010). Echinophoria Sacco, 1890. In: Bouchet, P.; Gofas, S.; Rosenberg, G. (2010) World Marine Mol ...

'' Sacco, 1890 *''

Eucorys ''Eucorys'' is a genus of large sea snails, marine gastropod mollusks in the family Cassidae, the helmet snails and bonnet snails. Species Species within the genus ''Eucorys'' include: * ''Eucorys barbouri'' (Clench & Aguayo, 1939) * ''Eucorys ...

'' Beu, 2008 *''

Galeodea ''Galeodea'' is a genus of large sea snails, marine gastropod mollusks in the subfamily Cassinae of the family Cassidae.Bouchet, P.; Gofas, S. (2011). Galeodea Link, 1807. Accessed through: World Register of Marine Species at http://www.marinespe ...

'' Link, 1807 *'' Microsconsia'' Beu, 2008 *'' Oocorys'' P. Fischer, 1883 *'' Phalium'' Link, 1807 - bonnet shells *'' Sconsia'' Gray, 1847 *'' Semicassis'' Mörch, 1852 ;Genera brought into synonymy : * ''Bathygalea'' Woodring & Olsson, 1957: synonym of ''Echinophoria'' Sacco, 1890 * ''Benthodolium'' Verrill & Smith

n Verrill N, or n, is the fourteenth letter in the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is ''en'' (pronounced ), plural ''ens''. History ...

1884: synonym of ''Oocorys'' P. Fischer, 1884 * ''Bezoardica'' Schumacher, 1817: synonym of ''Phalium'' Link, 1807 * ''Bezoardicella'' Habe, 1961: synonym of ''Phalium'' Link, 1807 * ''Cassidaria'' Lamarck, 1816: synonym of ''Galeodea'' Link, 1807 * ''Cassidea'' Bruguière, 1789: synonym of ''Cassis'' Scopoli, 1777 * ''Echinora'' Schumacher, 1817: synonym of ''Galeodea'' Link, 1807 * ''Euspinacassis'' Finlay, 1926: synonym of ''

'' Sacco, 1890 * ''Galeoocorys'' Kuroda & Habe, 1957: synonym of ''Galeodea'' Link, 1807 * ''Hadroocorys'' Quinn, 1980: synonym of ''Oocorys'' P. Fischer, 1884 * ''Morio'' Montfort, 1810: synonym of ''Galeodea'' Link, 1807 * ''Taieria'' Finlay & Marwick, 1937: synonym of ''Galeodea'' Link, 1807 * † ''Trachydolium'' Howe, 1926: synonym of ''Echinophoria'' Sacco, 1890 * ''Xenogalea'' Iredale, 1927: synonym of ''Semicassis'' Mörch, 1852 * ''Xenophalium'' Iredale, 1927: synonym of ''Semicassis'' Mörch, 1852 Image:Casmaria erinaceus forma vibex 01.jpg, ''

Casmaria erinaceus ''Casmaria erinaceus'', common name : the common bonnet, is a species of large sea snail, a marine gastropod mollusk in the family Cassidae, the helmet snails and bonnet snails. Description The size of an adult shell varies between 20 ...

'' Image:Cassis cornuta 01.jpg, '' Cassis cornuta'' Image:Cypraecassis rufa 01.JPG, ''

'' Image:Galeodea rugosa 002.jpg, ''

Galeodea rugosa ''Galeodea rugosa'', common name : the rugose bonnet, is a species of large sea snail, a marine gastropod mollusk in the family Cassidae, the helmet snails and bonnet snails. Description The shell size varies between 50 mm and 140&nbs ...

'' Image:Phalium bandatum bandatum 001.jpg, '' Phalium bandatum'' Image:Semicassis granulata granulata 01.JPG, '' Semicassis granulata''

Human uses

Some helmet shells are carved into cameos, starting in Italy in 1820. *The king helmet '' Cassis tuberosa'' was the first species to be made into cameos. * The black helmet '' Cassis madagascariensis'', also known as ''Cassis cameo'', has a dark brown or a claret-coloured shell layer under a yellowish outer layer. This gives it an

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 ...

appearance and makes it one of the most useful shells for cameos. * The red helmet ''

'' gives a

sardonyx 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 ...

-like appearance because it has

sard is a Japanese tuning company and racing team from Toyota, Aichi, mainly competing in the Super GT series and specialising in Toyota tuning parts. History The company was formed in 1972 as Sigma Automotive Co., Ltd by Shin Kato to develop and ...

-coloured bands under its pale outer coating. * The horned helmet '' Cassis cornuta'' produces a white figure on an orange background. It is also used as a trumpet by native Filipinos.

References

* Abbott, R.T. (1968). The Helmet Shells of the World (Cassidae) Part 1. ''Indo-Pacific Mollusca'' 2(9): 7-201 * Riedel F. 1995. An outline of Cassoidean phylogeny (Mollusca, Gastropoda). ''Contributions to Tertiary and Quaternary Geology'' 32(4): 97–132 * Kreipl K. 1997. ''Recent Cassidae''. Christa Hemmen, Wiesbaden, 151 p * Beu A.G. (2008) Recent Deep-water Cassidae of the World. A revision of Galeodea, Oocorys, Sconsia, Echinophoria and related taxa, with new genera and species (Mollusca, Gastropoda). In Héros V., Cowie R.H. & Bouchet P. (eds), ''Tropical Deep-Sea Benthos'' 25. ''Mémoires du Muséum National d'Histoire Naturelle'' 196: 269-387.

External links

* https://www.biolib.cz/en/taxon/id24557/ accessed 5 December 2017
Checklist of Mollusca

ITIS
* Steyn, D.G. & Lussi, M. 2005. ''Offshore Shells of Southern Africa'' * http://www.gastropods.com/Taxon_pages/Family_CASSIDAE.shtml#CASSIDAECASSINAE {{taxonbar, from=Q586745