The Cassidae are a

taxonomic 280px, Generalized scheme of taxonomy Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme of classes (a taxonomy) and the allocation ...

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

of medium-sized, large, and sometimes very large

sea snail Sea snails are slow-moving marine (ocean), marine gastropod Mollusca, molluscs, usually with visible external shells, such as whelk or abalone. They share the Taxonomic classification, taxonomic class Gastropoda with slugs, which are distinguishe ...

s commonly called helmet snails or bonnet snails. These are marine

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

mollusk Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The ...

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 Cassoid ...

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 ( limnic 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''.

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 or foreshore is the area above water level at low tide and underwater at high tide; in other words, it is the part of the littoral zone within the tidal range. This area can include several types of habitats with various ...

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. Spire ...

. 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: ) was a prominent Roman writer on agriculture in the Roman Empire. His in twelve volumes has been completely preserved and forms an important source on Roman agriculture and ancient Roman cuisin ...

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

varices A varix (: varices) is an abnormally dilated blood 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 ...

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

aperture In optics, the aperture of an optical system (including a system consisting of a single lens) is the hole or opening that primarily limits light propagated through the system. More specifically, the entrance pupil as the front side image o ...

. 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 i ...

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 animal of the phylum Echinodermata (), which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". While bilaterally symmetrical as larv ...

(especially

sea urchin Sea urchins or urchins () are echinoderms in the class (biology), class Echinoidea. About 950 species live on the seabed, inhabiting all oceans and depth zones from the intertidal zone to deep seas of . They typically have a globular body cove ...

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 Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...

and by rasping with their

radula The radula (; : radulae or radulas) is an anatomical structure used by mollusks 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 enters ...

. 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 arthropod mouthparts, mouthparts used for feeding and sucking. In vertebrates, a pr ...

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 (biology), family of medium-sized to very large sea snails, known as the tun shells. These are marine invertebrates, marine gastropod molluscs in the clade Littorinimorpha. The name ''tun'' refers to the snails' shell sh ...

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 Arthur Adams (1820 in Gosport, Hampshire – 1878) was an England, English physician and natural history, naturalist. Adams was assistant surgeon Royal Navy on board HMS Samarang (1822), HMS ''Samarang'' during the survey of the islands of ...

, 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. It is a ...

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'' Sacco, 1890 *'' Eucorys'' Beu, 2008 *''

Galeodea ''Galeodea'' is a genus of large sea snails, marine (ocean), 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 ...

'' Link, 1807 *'' Microsconsia'' Beu, 2008 *'' Oocorys'' P. Fischer, 1883 *'' Phalium'' Link, 1807 - bonnet shells *''

Sconsia ''Sconsia'' is a genus of large sea snails, marine gastropod mollusks in the family Cassidae The Cassidae are a taxonomic family of medium-sized, large, and sometimes very large sea snails commonly called helmet snails or bonnet snails. Thes ...

'' Gray, 1847 *'' Semicassis'' Mörch, 1852 ;Genera brought into synonymy : * ''Bathygalea'' Woodring & Olsson, 1957: synonym of ''Echinophoria'' Sacco, 1890 * ''Benthodolium'' Verrill & Smith n Verrill 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 '' Echinophoria'' 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'' Image:Cassis cornuta 01.jpg, '' Cassis cornuta'' Image:Cypraecassis rufa 01.JPG, '' Cypraecassis rufa'' Image:Galeodea rugosa 002.jpg, '' Galeodea rugosa'' 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 ''Cassis tuberosa'', the king helmet, is a species of very large sea snail with a solid, heavy shell, a marine gastropod mollusc in the family Cassidae, the helmet shells and their allies. Distribution This species occurs in the Western Atla ...

'' was the first species to be made into cameos. * The black helmet ''

Cassis madagascariensis ''Cassis madagascariensis'', common name the queen helmet, is a marine (ocean), marine gastropod mollusc in the family Cassidae, the helmet shells and bonnet shells. It is known for being the largest species of its family in the Atlantic Ocean. T ...

'', 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 is a typically black-and-white banded variety of agate, a silicate mineral. The bands can also be monochromatic with alternating light and dark bands. ''Sardonyx'' is a variety with red to brown bands alternated with black or white bands. ...

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

sardonyx Onyx is a typically black-and-white banded variety of agate, a silicate mineral. The bands can also be monochromatic with alternating light and dark bands. ''Sardonyx'' is a variety with red to brown bands alternated with black or white bands. T ...

-like appearance because it has

sard Carnelian (also spelled cornelian) is a brownish-red mineral commonly used as a semiprecious stone. Similar to carnelian is sard, which is generally harder and darker; the difference is not rigidly defined, and the two names are often used int ...

-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 {{Authority control