Despite its incorrect formation, the ICZN has placed the name Cassidae Latreille, 1825 on the official list offamily names, therefore avoiding homonymy with Cassididae Stephens, 1831 ; Opinion 1023.
Distribution
Species of this family occur in tropical and temperate seas from the intertidal zone to depths of 100 m, buried in the sand during the day and becoming active at night.
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. 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. Many species show blunt knobs and thickened axial ridges, known as varices. The thin, horny operculum is oval in shape and covers a long aperture. The siphonal canal 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.
Helmet bonnets prey on echinoderms, 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 acid secretion is provided by two large proboscis glands.
Taxonomy
In their taxonomy of the Gastropoda of 2005 Bouchet & Rocroi still listed Cassidae as Cassinae Latreille, 1825, a subfamily of TonnidaeSuter, 1913, following in this Riedel. In his "Revision of the deep-water Cassidae" however, Beu raised in 2008 Cassinae to the rank of family.
Bathygalea Woodring & Olsson, 1957: synonym of Echinophoria Sacco, 1890
Benthodolium Verrill & Smith , 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
Human uses
Some helmet shells are carved into cameos, starting in Italy in 1820.
The king helmetCassis 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 appearance and makes it one of the most useful shells for cameos.
The red helmet Cypraecassis rufa gives a sardonyx-like appearance because it has sard-coloured bands under its pale outer coating.
The horned helmetCassis cornuta produces a white figure on an orange background. It is also used as a trumpet by native Filipinos.
