Sculpture (mollusc)

The sculpture of a mollusc shell is the three-dimensional ornamentation on the outer surface, as distinct from the basic shape of the shell itself or colouration. Sculpture may be concave as well as convex. Sometimes it has microscopic detail. Sculpture refers to the calcareous outer layer, not the fleshy periostracum 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 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 - Folds on the columella.
• 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.
• Tubercle - Elevated knob-like projections or protrusions; larger than a pustule.
• Varicose - Bearing one or more varices.

References