Gastropod Shell - Shape of The Shell

Shape of The Shell

The distinction of the shape of the shell may vary, based on the purpose. For example distinguishing into three groups can be based on the height - width ratio:

• oblong - the height is much bigger than the width
• globose or conical shell - the height and the width of the shell are approximatelly the same
• depressed - the width is much bigger than the height

The following are the principal modifications of form in the gastropod shell.

• Regularly spiral:
  • Bulloid : bubble-shaped Bulla ampula
  • Coeloconoid : a slightly concave shell in which the incremental angle increases steadily during growth
  • Cone-shaped, obconic. Conus
  • Contabulate, short, with shouldered whorls
  • Convolute ; aperture as long as the shell, nearly or quite concealing the spire. Cypraea
  • Cylindrical, pupiform. Lioplax, Pupa
  • Depressed, lenticular. Ethalia carneolata
  • Discoidal. Elachorbis
  • Ear-shaped. Haliotis
  • Elongated, subulate, elevated. Terebra
  • Few-whorled. Helix pomatia.
  • Fusiform, spindle-shaped. Fusinus
  • Gibbous. Whorls swelled beyond the normal contour of increase (usually on the aperture side ). Streptaxis.
  • Globular. Natica
  • Many-whorled. Millerelix peregrina.
  • Short, bucciniform. Buccinum
  • Trochiform, pyramidal, conical with a flat base. Trochus
  • Turbinated ; conical, with rounded base. Turbo
  • Turrited, turriculated, babylonic ; an elongated shell with the whorls angulated or shouldered on their upper part. Turritella
• Scalariform, whorls not impinging. Epitonium
• Irregularly spiral, evolute. Siliquaria, Vermetus
• Tubular. Dentalium, or tooth-shell.
• Shield-shaped. Umbraculum
• Boat-shaped, slipper-shaped. Crepidula
• Conical or limpet-shaped. Patella
• Biconic : two conical shapes touching their bases and tapering at both ends : Fasciolaria tulipa
• Multivalve and imbricated. Chiton

• oblong shell of Bulgarica denticulata

• globose shell of Sphincterochila candidissima

• depressed shell of Escargot de Quimper

Detailed distinction of the shape can be:

• cap shape

• ear shape

• neritiform

• planispiral

• depressed trochiform or valvatiform

• trochiform

• ovate-conic

• conic

• elongate-conic or turriform or cockscrew shape

• top shape

• spindle shape - the sea snail Syrinx aruanus has the largest shell of any living gastropod.

• club shape

• barrel shape

• egg shape

• irregular shape

Pear shape means both shapes: ovate-conic and conic.