Glossary of Terms
Although probably nowhere near comprehensive, this Glossary of Terms should help beginners and experienced shellers come to terms with some of the most-used terms in Conchology.
Acentric: oblique, cutting growth lines at an angle.
Adductor Muscle: muscle responsible for closing the valves in bivales.
Anal Sulcus: notch or groove at or near posterior end of aperture.
Angulate: with an angular profile.
Annulate: with concentric rings.
Anterior: at or towards the front or head end of a shell; in gastropod shells it is the opposite end of the apex of the shell; in bivalves the anterior margin is on the opposite side of the ligament, i.e. where the foot protrudes.
Aperture: the shell opening.
Apex: posterior tip of shell.
Articulamentum: porcellaneous inner layer of chiton shell.
Articulated: (a) colour lines consisting of a series of joint-like markings; (b) valves hinged together.
Attenuate: slender tapering.
Axial: lying in-line with apex-base axis.
Axial Sculpture: shell feature or sculpture running parallel to the axis of coiling.
Axis: an imaginary line through the apex of a gastropod shell, about which the whorls are coiled.
Banding: color marking in continuous stripes.
Base: lower part, anterior side of it.
Bead: a rounded granule or tubercle.
Beak: (a) tip of the umbo in bivalves; (b) apex of a valve in chitons; (c) entire siphonal rostum in gastropods.
Bifid: divided in two by a notch or groove.
Bivalve: any mollusc having two valves or shells that are hinged together, as in mussels and clams.
Body Whorl: the most recently formed whorl of a spiral shell terminating in the aperture; usually the largest whorl of a spiral shell.
Bulbous: swollen, bulb-shaped.
Byssal Notch: notch on anterior side of a bivalve through which the byssus passes.
Byssus: bunch of chitinous threads anchoring members of some bivalve groups.
Callus: a thick, usually shiny secondary deposit of calcium.
Capuliform: cap-shaped, with recurved apex.
Cardinal Area: dorsal surface between hinge margin and umbo, usually bearing the external ligament.
Cardinal Tooth: a hinge-tooth situated beneath the umbo in bivalves.
Cephalopoda: one of the seven classes of molluscs (squids, octopus, argonauta, spirula).
Ceratus: a spur near base of outer lip.
Chambered: having divisions across the hollow of the shell, separating or dividing the shell into chambers.
Chiton: the coat-of-mail shells (Polyplacophora); they possess a shell made up of eight shell plates.
Chomata: small tubercles along edge of valves.
Cilia: microscopic filaments.
Cingulum: spiral cord, especially one bordering the suture.
Columella: central axis of a gastropod shell, lower part of inner lip.
Concentric: parallel to the line of growth.
Conchologist: one who collects and/or studies shells.
Conchology: the study of marine, fresh-water and land-shells; the arrangement and description of molluscs based upon a study of the hard parts only.
Convolute: spire completely hidden by last whorl, but not sunken to form an umbilicus.
Cords: coarse, rounded spiral or transverse linear sculptures on the shell surface.
Costa: a rib.
Crenate: regularly notched or scalloped.
Crenulate: with regular fine notches or folds.
Cusp: small, often tooth-like projection.
Deltoidal: more or less triangular.
Dendritic: branched like a tree.
Denticle: a small tooth.
Denticulate: with small teeth.
Depressed: low in proportion to diameter.
Detritus: surface deposits, consisting largely of decaying organic matter.
Dextral: with a right-handed spiral.
Digitation: a finger-like projection.
Disjunct: successive whorls not in contact.
Distal: at the end of.
Divaricate: sculpture diverging or splitting, usually along a line.
Domed: low, broad and rather gently rounded.
Dorsal: on upper side.
Dorsal Sulcus: groove or line down centre of back in Cypraeidae.
Dorsum: back or upper side.
Elongate: extended; considerably longer in one dimension than another.
Endemic: restricted to a certain geographical area.
Equivalve: with equal valves.
Ex Pisce: removed from the gut of a fish.
False Umbilicus: a shallow depression at the base of the body whorl, not penetrating into the columella.
Fasciole: band or ridge encircling the base, formed by the growth of the siphonal canal.
Fimbriated: fringed or regularly crenulated.
Fissure: slit or notch.
Flame: mark that tapers to a point.
Flange: an erect, projecting flattened ridge.
Foramen: perforation or opening.
Fossa: deep groove.
Fossula: shallow longitudinal furrow situated towards front end of inner lip in Cypraeidae.
Fossular Ridge: ridge bordering the fossula.
Foveolated: with small pits.
Frond: leaf-like extension.
Fusiform: tapering at both ends.
Gape: space left between margins of valves when they are closed.
Gastropoda: a class of molluscs; scientific term for molluscs which have undergone torsion.
Gemmulate: with small beads.
Gibbose: very swollen, hump-backed.
Girdle: the tough mantle enclosing a chiton shell.
Globose/Globular: rounded or spherical.
Gradate: whorls rising in steps.
Granulose: with fine grain-like beads.
Growth Lines: fine axial or concentric lines indicating previous growing margin.
Guttered: with wide, shallow grooves.
Helical: spirally coiled.
Hinge Plate: platform on inner dorsal margin bearing hinge-teeth.
Holotype: the original type; the single specimen upon which a species is based.
Imbricate: overlapping like roof tiles.
Imperforate: without umbilicus.
Impressed: indented; sunken.
Incised: sculptured with one or more sharply cut grooves.
Incrustation: an irregular deposit on the shell surface.
Inductura: parietal shield.
Inflated: swolelen; stronlgy convex.
Inflexed: turned inward.
Intercostal: placed or occurring between the ribs.
Interspace: interval between ribs or ridges.
Interstices: gaps or pits between ridges or teeth.
Intervarical: between two varices.
Involute: spire completely enveloped by last whorl, leaving an apical umbilicus.
Iridescent: colours resulting from light refraction, not pigmentation.
Isodont: with a few symmetrically arranged hinge-teeth.
Jagged: with sharply uneven edge.
Junior Synonym: the later of two names.
Labial: pertaining to the inner lip.
Labium: inner lip.
Labral: pertaining to the outer lip.
Labrum: outer lip.
Lamella: a thin, flattened plate.
Lanceate: shaped like a spearhead.
Lateral: on the side.
Lectotype: a specimen subsequently selected from a series of syntypes and officially designated as such.
Lenticular: shaped like a convex-sided disc.
Ligament: horny, elastic structure joining hinges or two valves together.
Linear: long, narrow and parallel-sided.
Lira/Lirae: a ridge (ridges).
Lobate: with lobes.
Malacologist: one who studies the mollusc animal along with the shell.
Malacology: the study of molluscs (clams and snail) based on soft anatomy; the branch of zoology that deals with molluscs, the animal within the shell.
Malleate: having a hammered appearance.
Mantle: fleshy fold responsible for shell growth.
Mantle Line: the line on the dorsal surface of a cowrie shell where the mantle lobes meet.
Margin: extreme edge of valve of bivalve shells; also the thickened periphery of base of some gastropods, notably cowries; sometimes used as equivalent to edge.
Median/Medial: on the mid-line.
Nacre: the pearly or iridescent substance which lines the interior of some molluscs shells.
Naticiform: shaped like a natica.
Neotype: specimen designated as a new type when the holotype has been lost.
Node: a knob.
Nodule: small knob.
Nodulose: with small knobs.
Nomenclature: a system of names.
Nuclear Whorl: whorl of the protoconch.
Nucleus: earliest part of operculum.
Operculum: a horny or shelly (calcareous) plate or disc attached to the back of the foot used to close the aperture, wholly or partially, when the animal withdraws into its shell.
Ornament: surface sculpture standing out in relief on shell surface.
Ovate: oval shaped.
Palatal: pertaining to interior of outer lip.
Papilla: nipple-shaped projections.
Paratype: type-specimens, other than the holotype.
Parietal Region: part of inner lip posterior to columella.
Pelagic: pertaining to or living in the open sea far from land; free-swimming or floating.
Periostracum: the outer skin or horny covering on the exterior of many shells. May be thin and transparent or thick, fibrous or hairy.
Periphery: the widest part of a whorl where it bulges most.
Peristome: whole margin of aperture.
Pinnate: with side-branches.
Plait: a fold or ridge.
Pliculate: with fine ridges.
Posterior: the rear or tail end of an animal.
Proboscis: prolonged snout of carnivorous gastropods bearing the mouth at the tip.
Protoconch: the embryonic shell of a gastropod forming the tip of the spire.
Punctate: with punctuations.
Pupiform: barrel-shaped or swollen in the middle.
Pustulose: with pustules.
Radial: arranged like the spokes of a wheel.
Radula: a rasp-like organ, odontophore or lingual ribbon of armed with tooth-like processes, found in nearly all molluscs except the bivalves; this tough chitinous ribbon of teeth obtains food particles by a rasping or licking action.
Recurved: curved backwards.
Reticulate: with a network of obliquely intersecting ridges.
Rhombic: roughly diamond-shaped with rounded corners.
Rib: a ridge.
Riblet: small rib.
Rostrate: with a rostum.
Rostum: beak-like projection.
Rugose: rough or wrinkled.
Scabrous: rough like a file.
Scalariform: loosely coiled, and not in contact with one another.
Scaphopoda: tusk or tooth shells; this class of molluscs possess an one-piece tapering, curved shell open at both ends and an elongated foot adapted for burrowing.
Sculpture: the decoration (in terms of ridges, ribs, striae, etc) on the surface of a shell; a pattern of raised or depressed markings on the shell's surface.
Shell: a hard rigid, calcareous or chitinous structure encasing an animal, or covering some part of it.
Shoulder Slope: slope between shoulder and suture above.
Sinistral: having the whorls of a spiral shell turning towards the left when a shell is held with its apex pointed up and its aperture facing the viewer; this is a counter-clockwise whorl.
Siphonal Canal or Notch: a tube-like extension or notch-like furrow in the at the anterior end of the lip in a gastropod shell.
Spatula: central area within muscle scar in limpets.
Spicule: a hard, sharp object, often needle-like.
Spiral Sculpture: a sculpture following the helical growth of a gastropod shell.
Spire: all whorls of a spiral shell exclusive of the body whorl.
Stepped: with flat shoulder so that the whorls ascend like steps.
Striae: fine lines, threads or grooves.
Striate: with striae.
Stromboid Notch: with a shallow notch near base of outer lip in Strombidae.
Subulate: tapering very gradually to a sharp point.
Sulcus: a groove.
Suture: the spiral groove where two adjacent whorls are joined.
Syntype: any specimen from a type-series for which no holotype was designated.
Taxon/Taxa: group of organisms with own scientific name.
Teleoconch: all the whorls of a gastropod shell after the protoconch.
Thread: fine ridge.
Transverse: at right angles to main axis.
Trema: a hole in the shell for the exhalent current in haliotis shells.
Trochiform: top-shaped with flat sides.
Truncate: ending abruptly.
Tubercle: elevated knob.
Turbiniform: top-shaped with convex sides.
Turriculate: sharply conical with numerous, rather flattened whorls.
Umbilicate: navel-like; with depressed cavity.
Umbilicus: a perforation, usually in the base of the central axis.
Umbo: the curved dorsal peak of a valve.
Undulate: having a wavy surface.
Univalve: a mollusc consisting of a single spirally coiled shell.
Valve: one of the separate portions of a shell of a mollusc. In bivalves, one of the two portions into which the shell is divided, the two valves usually joined by a hinge. In chitons, one of the eight plates comprising the shell.
Varical: pertaining to a varix.
Varix: a rib-like thickening of the outer lip due to periodic arrested growth of the shell.
Ventral: on the underside.
Ventricose: strongly swollen.
Verrucose: with wart-like tubercules.
Vesicle: a bubble-like sac or hollow chamber.
Volution: a whorl.
Whorl: a single, complete turn of 360° in the spiral growth of a gastropod shell.
Wing: prominent angular extension of the dorsal margin in a bivalve.