Aperture: the opening in the body whorl of a snail shell.
Axial ribs: sculpture in the same direction as the axis (i.e. from the apex to the base) of a snail shell; axial ribs are parallel to the edge of the outer lip of the aperture.
Beak (umbo): the earliest part of the shell (bivalve) formed.
Bilobate: having two lobes (protuberances).
Body whorl: the lowermost (largest) whorl of a snail shell.
Callus: a swelling or deposit of calcareous or enamel-like material.
Cancellate: crisscrossing lines of sculpture, usually perpendicular to each other.
Concentric ribs: sculpture that is parallel to the margin of the shell.
Crown: the part of the tooth that is covered by enamel and is usually exposed in the mouth.
Cusplets: small cusps.
Hinge: the elongate shell ridge, usually with teeth, where the valves are joined or interlocked.
Inequilateral: the two sides of a single valve are of different length and/or shape.
Inequivalve: the two valves of a bivalve are of different size and shape.
Lingual face: the part of the tooth that faces the tongue, the internal side (as opposed to labial, or external).
Node: a small, knob-like hump or projection.
Occlusal face: the part of the tooth that is the wear surface, it is worn by abrasion from other teeth (above, below) during chewing.
Outer lip: the apertural margin of the last part of the body whorl of a snail shell.
Radial ribs: sculpture that fans out from the umbo (beak) to the margins of the shell.
Reticulate: crisscrossed network of sculpture.
Root: the part of the tooth that is below the enamel within a socket of the jaw or skull—not exposed in the mouth.
Sculpture: a pattern of raised or depressed markings on the shell surface.
Siphonal canal: a tubular prolongation at the base of the aperture that contains the siphon.
Spiral: sculpture of revolving lines in the direction of the turning of whorls in a snail shell.
Teeth (dentition): the shelly protuberances on the dorsal margin of a valve which fit into corresponding sockets of the opposite valve.
Transverse groove: a groove running across a tooth, from side to side.
Umbilicus: a small hole or depression in the base of the body whorl of a snail shell.
Whorl: a complete turn of volution of a snail shell.