Mollusca Glossary

Gastropoda: Glossary

Abbreviated Dendrogram
Mollusca ├─Aculifera └─Conchifera ╘═Helcionelloida └─┬─Bellerophontoidea └─Gastropoda (crown group) ╞═Eogastropoda (paraphyletic or polyphyletic) │ ├?─Macluritoidea │ ├?─Euomphaloidea │ └─Patellogastropoda └─Orthogastropoda ├─Vetigastropoda ├─Neritimorpha └─┬─Caenogastropoda └─Heterobranchia ├─Opisthobranchia └─Pulmonata

Gastropod radulas
Systematics Gastropoda


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Acuminate Gradually tapered to a point. Sharply pointed.

Acute Sharply angled. Sharp; a spire with an angle of less than ninety degrees.

anistrophic - a shell which is spirally coiled and is asymmetrical.

Anal canal: An opening in the gastropod shell through which excrement is expelled.

Anterior: an-te'ri-or (L ante=before)   at or towards the front or head end of a shell.

Anterior canal: An open or closed tubular shell extension at the anterior end of a shell, through which the siphon is extended. Same as siphonal canal

Aperture   ap'er-ture (L apertures=an opening)   The major opening of a univalve shell (gastropod, paragastropod, cephalopod, etc).

Apical whorls Those whorls near the apex.

Apex   a'pex (L apex=the tip, summit)   the tip of the spire of a gastropod and generally consists of the embryonic shell.

Apical cavity A space under the apex of patellate gastropods.

Axial Pertaining to or more or less parallel to the axis of coiling. Parallel, or nearly so, with the shell axis. Longitudinal, following the direction of the axis of the shell. Longitudinal ribs or color bands. In the same direction as the axis; from apex to the base of a snail shell. Axial ribs are those parallel to the edge of the outer lip. Transverse is a preferred term. In gastropods, running parallel to the shell's axis, or from spire to base.

Axial sculpture 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.


Bead A small, more or less hemispherical protuberance resembling a bead. Beads are smaller than nodules.

Beaded Sculptured so as to resemble beads, or strings of beads.

Body whorl The most recently formed whorl of a spiral shell, terminating in the aperture.

Buccal Pertaining to the organs of the mouth area in gastropods, especially to the bulging flexible mass that supports the radula.

Buccal bulb The bulging mouth extension carrying the ribbon of teeth (radula).

Buccinid or Buccinoid Like the whelk Buccinum.


Ceras   cer'as  (Gr Keras = horn)  a horn or horn like appendage located on nudibranchs

Columella col-u-mel'la. The thickened axial pillar around which the whorls of univalves are built.

Conch (L concha = shell)  a trumpet shell; a large marine mollusks with a univalve shell

Coronate Encircled by a row of spines or prominent nodes, especially at the shoulder of the last whorl in gastropods.


Detorsion de-tor'sion. the act of twisting back or removing torsion;  unwinding

Dextral dex'tral  (L dexter = to the right)   Having the aperture on the right side of the shell when the apex is upwards and the aperture is facing you.  The whorls spiral in a clock-wise manner.

Digitation Finger-like projection outwards from outer lip.

Dorsal dor'sal  (L dorsum = the back)  The back of a gastropod remote from the aperture;  The conical top surface of a limpet


Estivate es'ti-vate  (L aestivare = to spend the summer)   to pass the summer in a state of torpor;  the dormancy in the summer of some lank snails.


Foliated Having branched or crimped outer ends; applied to the appearance of spines of certain gastropods such as some Muricidae.

Fusiform Spindle-shaped with a long canal and an equally long spire, tapering from the middle toward each end; applied to univalves as in the genus Fusinus.



Height In gastropods (except in cowries) the distance from the embryonic whorls or apex to the siphonal canal (the term "length" is also used).





Heterostrophic Apical whorls coiled opposite to adult whorls.

Labial teeth Tooth-like processes around the aperture of some gastropods, notably cowries.

Labrum or Labial lip Outer lip or right margin of aperture of univalves.

Lip(s) In gastropods, the margin of the aperture: the inner lip (labium) extends from the base of the columella to the suture and is divided into a columellar lip and a prietal lip; the outer lip (labrum) is that part of the lip furthest from the axis of coiling.

Lira (plural lirae) Fine linear elevation of shelly material usually within outer lip of some gastropod shells.

Lirate Sculptured with fine (or thread-like) lines or grooves.



Nodule A rounded protuberance on the shell sculpture; larger than a bead.

Nodose, Nodulose or Nodular Bearing rounded protuberances on the shell; sculptured with small tubercles, knobs, nodes or projections.

Nuclear tip The apex of a gastropod shell.

Nuclear whorl(s) Small, and generally smooth and unsculptured whorls which have been formed within the egg and which constitute the apex of gastropod shells.

Nucleus Earliest formed part of a shell or operculum. In gastropods, the initial whorls of the shell (protoconch) or the first-formed portion of an operculum; in bivalves, the prodissoconch.


Operculate;  having an operculum

Operculum o-per'cu-lum. A horny or shelly (calcareous) plate attached dorsally to the foot serving to close the aperture, wholly or partially, when the animal withdraws into its shell. A chitinous or calcareous plate present in many mollusks.  

Ornament Surface sculpture standing out in relief on shell surface.

Osphradium "a sense organ located in the mantle cavity close to the gill; in the Archaeogastropoda and Mesogastropoda it consists of sense cells arranged in groups, in the Neogastropoda it is a complex organ with comb-like lamellae and hair cells that react to chemical stimuli. It has also been held that the osphradium is used to indicate the amount of suspended matter in the water." [Lindner 1975 p.22]

Outer lip The lip of the aperture of a gastropod shell furthest from the shell axis. The outer lip itself has inner and outer surfaces.


Phaneromphalus having a very large or prominent umbilicus

Plait Spiral fold or ridge on the columella. Plica.

Plica (plural plicae) Fold or ridge on the columella, a less conspicuous feature than columella fold but the two terms are more or less interchangeable.

Plicate Folded or twisted or bearing plaits. Folded or plaited. Bearing plicae; also occasionally used here as equivalent to crenulate.

Plication(s) A raised ridge, fold, or plait, especially on the columella of a gastropod shell.

Plicate Folded or twisted; having plicae.

Posterior The rear or tail end of an animal; in a gastropod shell, towards the apex.

Posterior canal Anal canal; Notch, or trough-like or tubular extension of the posterior aperture margin supporting the excurrent siphon.

Propodium pro-po'di-um  Latinized Gr  Pro- = before + -podis = foot)   The foremost division of the foot of a gastropod used to push aside sediment as the animal crawls.

Protoconch pro'to-conch  (Gr  Proto = first;  konche=shell)  The embryonic shell. It is present in the adult as the apical or nuclear whorls and often demarcated from the teleoconch whorls by a change of sculpture, design, texture or colour..



Reticulate Lines, riblets, threads or grooves crossing each other like a net.

Rib An elongate sculptural element of a shell, raised above the surrounding surface. A fine rib is a riblet, and a very fine rib is a thread.

Riblet A small rib, but coarser than a thread.

Selenizone Spiral band of crescentic growth lines, associated with marginal slit or foramen in certain univalves Pleurotomariine, Bellerophontid, etc).

Sinistral sin'is-tral  (L  sinister=left)  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.


Sinus si'nus  (L  sinus=a curve)  A depression, bend, embayment;  a recess or indentation.

Siphonal Canal, siphonal notch   A tube-like extension or notch-like infolding of the lip of the aperture in a gastropod shell, often continuous with columella, also known as an anterior canal, through which the inhalant (anterior) siphon is extended.

Slit  (AS  slite=slit0  A shallow or relatively long incision in the outer margin of the aperture of a gastropod.

Spiral sculpture Sculpture following the helical growth of a gastropod shell.

Spire All whorls of a spiral shell exclusive of the body whorl.

Stria (Pl. striae). Narrow and shallow incised groove.

Striate Marked with striae.

Suture The continuous spiral line of junction of the whorls.


Taenioglossa A term for a group of mollusks equipped with a radular ribbon containing generally seven longitudinal rows of teeth (i.e. Cypraeidae, Cymatiidae). Radula with each row consisting of a central, a lateral, and a pair of marginal teeth.

Teleoconch All the whorls of a gastropod shell after the protoconch.

Thread A very fine sculptural element of a shell, raised above the surrounding surface. Finer than a rib.

Trochiform, Trochoid or Trochoidal Conically shaped, like an inverted spinning top, or like the shell of a Trochus having a pointed spire, flat sides and flat base.

Tubercle(s) Elevated knob-like projections or protrusion; larger than pustule.

Turbinoform, Turbinate Turban-shaped, with broadly conical spire and convex base, as in shell of Turbo.

Turreted With the spire whorls like a succession of turrets, emerging one above the other, having a very high spire, the base usually flattened or slightly convex. In gastropods, tower-shaped, with a long spire and somewhat shouldered whorls.

Turriculate Having the form of a turret; tower-shaped; spire whorls regularly stepped in outline forming a long spire with somewhat shouldered whorls; as in terebra.

Turriform With a many whorled, slender spire.


Umbilicate Navel-like; with depressed cavity. Having an umbilicus.

Umbilicus um-bil'I-cus  (L  umbilicus=naval    Gr  corde=string) Cavity or hollow around the axis of a gastropod shell, the hole around which the inner surface of a gastropod shell is coiled; a pit or chink in the shell next to or within the base of the Columella, formed when the inner walls of successive whorls do not meet. The opening at the base of a hollow columella, surrounded by the base of the body whorl.

Uncinus (plural uncini) In gastropods, a marginal or lateral tooth on the radula, more or less hook-like in shape.

Undulate: Having a wavy surface.


Varicose Bearing a varix or varices.

Varical Pertaining to a varix.

Varix (Pl. varices). An thickened or elevated axial ridge in certain gastropods, more prominent than ribs and generally more widely spaced, formed by thickening of the outer lip at a resting stage in the growth of the shell

Velum Ciliated mantle flap by which a molluscan larva swims.

Ventral ven'tral  (L venter=the belly)   Of, pertaining to, or situated on, the lower side of a dorsoventral organism; on the aperture surface of a gastropod shell; Opposite to dorsal.


Whorl A single, complete turn of 360° in the spiral growth of a gastropod shell.





(from Man and Mollusc Glossary)

AS       =          Anglo-Saxon
Fr        =          French
Gr        =          Greek
L          =          Latin

Links and References

Glossary/Mollusks - a very comprehensive glossary

Man and Mollusc Glossary - includes derivation of original word

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