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Taxon profile

species

Cassis cornuta Linnaeus, 1758

kingdom Animalia - animals »  phylum Mollusca - mollusks »  class Gastropoda - gastropods »  order Caenogastropoda »  family Cassidae

Images

Description

Adult shell large, 175 to 348 mm. (7 to 14 inches) in length, rotund, with a row of 5 to 7 large or small spines on the shoulder, with a large, oblong, heavy parietal shield, and with a heavy outer lip bearing 5 to 7 large whitish teeth on the central inner edge. Nuclear whorls 2-1/2, minute, bulimoid, opaque-white, smooth, and with a brown suture in the first whorl. Post-nuclear whorls with 5 to 7 irregular, poorly beaded spiral threads. The first varix is produced in the 7th or 8th whorl. Adults with 7 or 8 former varical lips in the spire. Body whorl with 3 or 4 spiral, raised ridges, the upper one on the shoulder bearing 5 to 7 long or short, pointed or broad knobs, while the 2 cords below each bear 3 or 4 very small knobs. There may be an additional low, spiral cord near the base. Outer surface of whorls minutely pitted. Parietal shield heavy, broadly or narrowly elongate, yellowish or brownish orange, with two spotted spiral cords and the surface pitting showing through the central region. Lower half of columella with 8 to 11 poorly developed, whitish, spiral plicae. Outer lip heavy, broad, glossy, cream to orange and with 5 to 7 large teeth on the inner edge in the central region. Posterior side of outer lip usually with 7 broad patches of brown. Umbil-icus usually sealed; true umbilicus usually open and containing trapped pieces of loose coral, stones or pieces of shells. Siphonal canal fairly long and pointing upward. In young specimens less than 60 mm. in length: inner columella with about 14 small, short, spiral plicae; inside of outer lip with 10 to 12 small denticles along the entire length of the outer lip; body whorl maculated with brown and with cancellate sculpturing in which the axial ribs predominate. Operculum chitinous, brown, elongate-oblong and about 1/4 the length of the aperture.

Distribution

Range—East Africa to Polynesia; Japan to Australia. Its distribution broadly coincides with that of coral reefs of the Indo-Pacific.
Remarks—The Horned Helmet is the largest and most widespread of the Indo-Pacific Cassidae. It reaches a length of 14 inches. It is characterized by its large, orange-yellow parietal shield, the row of 5 to 7 knobs on the shoulder of the dorsum, and by the numerous honeycomb-like pittings on the outer surface. Although the shells are variable in several characters, particularly in the coloration and shape of the parietal shield and in the size and number of knobs on the shoulder, I can recognize no consistent differ-ences between Red Sea, East African and Poly-nesian specimens.
In some areas particularly Hawaii, there appears to be considerable sexual dimorphism in the shells, the males being smaller, less ovate, and having larger and fewer knobs on the dor-sum. Young specimens have 9 to 13 small, uniform-sized knobs on the shoulder.
The shell is used by the natives of the South Seas as a container for liquids. It is a popular household shell ornament in many parts of the world, but does not lend itself to cameo carvings.
When shaking a cleaned specimen, one can sometimes hear a small, trapped object inside that defies release even though the shell is slowly rolled in a counterclockwise direction. This has led some shell collectors to suppose that a pearl or piece of broken shell was trapped inside by former varices. However, the object is usually a piece of coral, stone, or shell trapped inside the umbilical region and not within the apertural opening or cavities of the early whorls.
Habitat—Cassis cornuta Linne occurs in colonies at depths from 1 to 15 fathoms where the bottom consists of sand and broken coral rock. During periods of inactivity, or perhaps while feeding, they may be partially buried be-low the surface of the sand. They probably feed on echinoderms. Robert C. Guest reports that "they are more active at night, and when moving they lift their shells straight up, move forward, then drop their shells down."

Sources

Abbott: Indo-Pacific Mollusca. The Helmet Shells of the World.
Author: Jan Delsing

Links and literature

EN Galli C.: WMSDB - Wolrdwide Mollusc Species Data Base July 10, 2013 [http://www.bagniliggia.it/WMSD/WMSDhome....] [as Cassis cornuta Linnaeus, 1758]
Data retrieved on: 23 November 2013
CZ Pfleger V. (1999): České názvy živočichů III. Měkkýši (Mollusca), Národní muzeum, (zoologické odd.), Praha, 108 pp. [as Cassis cornuta (LINNÉ, 1758)]
Data retrieved on: 11 November 2013

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