The sculpture of a mollusc shell

Mollusc shell

The mollusc shell is typically a calcareous exoskeleton which encloses, supports and protects the soft parts of an animal in the phylum Mollusca, which includes snails, clams, tusk shells, and several other classes...

 is the three-dimensional ornamentation on the outer surface, as distinct from the basic shape of the shell itself

Mollusc shell

The mollusc shell is typically a calcareous exoskeleton which encloses, supports and protects the soft parts of an animal in the phylum Mollusca, which includes snails, clams, tusk shells, and several other classes...

 or colouration. Sculpture may be concave as well as convex. Sometimes it has microscopic

Microscopic

The microscopic scale is the scale of size or length used to describe objects smaller than those that can easily be seen by the naked eye and which require a lens or microscope to see them clearly.-History:...

 detail. Sculpture refers to the calcareous

Calcareous

Calcareous is an adjective meaning mostly or partly composed of calcium carbonate, in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines.-In zoology:...

 outer layer, not the fleshy periostracum

Periostracum

The periostracum is a thin organic coating or "skin" which is the outermost layer of the shell of many shelled animals, including mollusks and brachiopods. Among mollusks it is primarily seen in snails and clams, i.e. in bivalves and gastropods, but it is also found in cephalopods such as the...

 which may be textured even if the underlying shell is smooth. In many taxa the shells have no sculpture apart from fine growth lines.

Terms

• Axial sculpture - Sculpture running parallel to the axis of coiling, an imaginary line through the apex of a shell about which the whorls are coiled.
• Bead - A small hemispherical protuberance resembling a bead, similar to but smaller than a nodule.
• Beaded - resembling rows or strings of beads.
• Growth line - A fine transverse
  Transverse plane
  The transverse plane is an imaginary plane that divides the body into superior and inferior parts. It is perpendicular to the coronal and sagittal planes....
  
   line marking the growth of the shell.
• Lira, Lirate - ornamented with fine thread-like lines or grooves.
• Longitudinal sculpture - Sculpture following the direction of the axis of the shell.
• Nodule - A rounded protuberance on the shell sculpture; larger than a bead.
• Nodose, Nodulose, Nodular - Bearing small rounded protuberances or tubercules.
• Ornament - Can refer to surface sculpture standing out in relief on shell surface; or simply to sculpture as a whole.
• Plait
  Plait (gastropod)
  A plait is an anatomical feature which is present the shells of some snails, or gastropods. This sculpture occurs often in the shells of marine gastropod mollusks in the clade Neogastropoda, but it is also found in some pulmonate land snails....
  
  - Folds on the columella
  Columella
  Lucius Junius Moderatus Columella is the most important writer on agriculture of the Roman empire. Little is known of his life. He was probably born in Gades , possibly of Roman parents. After a career in the army , he took up farming...
  
  .
• Pustule - A very fine knob-like protrusion, smaller than a tubercule.
• Reticulate - Sculpture consisting of a criss-crossing network of riblets, threads, or grooves.
• Rib - A strong ridge on the surface of the shell.
• Riblet - Smaller than a rib, but coarser than a thread.
• Spiral sculpture - Sculpture following the spiral growth of the shell.
• Stria (plural striae) - A shallow incised groove.
• Striate - Ornamented with striae.
• Thread - A very fine riblet.
• Transverse sculpture - Sculpture parallel to the edge of the outer lip of the aperture
  Aperture (mollusc)
  The aperture is an opening in certain kinds of mollusc shells: it is the main opening of the shell, where part of the body of the animal emerges for locomotion, feeding, etc....
  
  .
• Tubercle - Elevated knob-like projections or protrusions; larger than a pustule.
• Varicose - Bearing one or more varices
  Varix (mollusc)
  A varix is an anatomical feature of the shell of certain sea snails, marine gastropod molluscs.It is a thickened axial ridge in the shell of some families of gastropods. A varix is located at intervals around the whorl, and is formed by considerable thickening of the outer lip at a resting stage...
  
  .