Archerd Shell Collection > Shell Classes > Gastropoda > Cassidae


Family: Cassidae (Helmet Shells)


Description
 
The Helmet Shells are heavily constructed, large or medium size shells with a rather short spire and a well-developed final whorl. The body whorl is voluminous, and often ornamented with knobs and varices (lengthwise ribs). The callus is well developed and extends over the entire ventral surface. Coarse teeth on the inner side of the lip and several prominent columellar folds are common, but not invariable.
Defining characteristics are: outer lip thickened and recurved on the dorsal surface to form a prominent helmet-like rim; and, a short syphonal canal bent backwards and opening toward the dorsal surface. The Family contains eighty or more living species that  live in warm waters around the world. 
 
This snail has a dramatic way of feeding on sea urchins. It creeps up slowly, raises its shell quite high, then abruptly drops the heavy shell in such a way that the urchin is completely engulfed. The urchin spines are covered by a three-layered thin "skin"in communication with poison glands that can quickly release toxins as the spine penetrates the predator. However, the the helmet snail first releases a paralytic enzyme from its salivary gland, which protects it from the toxins. Then, the snail secretes sulfuric acid sufficiently strong to dissolve the sea urchin shell. In about 10 minutes its meal has been consumed.
 
Classification:
Class: Gastropoda
Clade: Littorinimorpha
Superfamily: Tonnoidea
Family: Cassidae
Major Genera
  • Genus: Casmaria
  • Genus: Cassis
  • Genus: Cypraecassis
  • Genus: Galeodea
  • Genus: Galeoocorys
  • Genus: Morum
  • Genus: Oocorys
  • Genus: Phalium
  • Genus: Sconsia
Phalium_glaucum.JPG (48896 bytes)
Phalium glaucum (Linnaeus, 1758)
Gray Bonnet

 

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Archerd Shell Collection > Shell Classes > Gastropods > Helmet Shells