| Mollusca | ||
| Metazoa | Glossary |
| Phylogeny | Metazoa | Mollusca | ||
| Annelida |
◄─┬─Aculifera
└─Conchifera |
Mollusca | Mollusca | Platyzoa |
|
Abbreviated Dendrogram
Spiralia
├─Brachiopoda
└─┬─Annelida
│
└─Mollusca
├─Aculifera
│ ╞═Mattheviidae
│ │ └─Aplacophora
│ └─Polyplacophora
└─Conchifera
╞═Tryblidiida (Monoplacophora)
│ └─Cephalopoda
╘═Helcionelloida
╞═Rostroconchia
│ └─Scaphopoda
├─Bivalvia
└─Gastropoda
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Adapical Toward shell apex along axis or slightly oblique to it.
Adductor muscle(s) Anterior and posterior muscles that close a bivalve shell. In a bivalve, the muscle, either one or two, connecting valves and drawing them together.
Annulated Marked with rings.
Annulation or Annular ring A growth increment in a tubular shell marked by regular constrictions (e.g., caecum).
Anterior an-te’ri-or (L ante=before) situated in front, in lower animals relatively nearer the head; At or towards the front or head end of a shell.
Anterior extremity or margin Front or head end of animal or shell. In gastropod shells it is the front or head end of the animal, i.e. 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 ap’er-ture (L apertures=an opening) The major opening of a univalve shell (gastropod, paragastropod, cephalopod, etc).
Apical pertaining to the apex.
Apical whorls Those whorls near the apex.
Apex, Apexes or Apices a’pex (L apex=the tip, summit) the tip of the spire of a gastropod and generally consists of the embryonic shell. First-formed tip of the shell. The beginning or summit of the shell. The beginning or summit or the gastropod spire. The top or earliest formed part of shell-tip of the protoconch in univalves-the umbos, beaks or prodissoconch in bivalves. In gastropods, the tip of the spire; in tusk shells, the small, open hind end.
Apical At the apex, point or tip.
Aragonite A mineral composed, like calcite, of calcium carbonate, but differing from calcite in certain characters of crystallization, density, and cleavage.
Articulated ar-tic’u-lated (L articulatus=jointed) the union forming a joint as the interlocking teeth of the hinge plate in bivalves
Articulamentum Internal layer of a chiton shell. In chitons, the middle shell layer.
Asymmetrical as-ym-met’ri-cal (Gr a=priv.; syn=with; metron=measure) not even on both sides of an axis, bilaterally uneven, lack of symmetry
Attachment scar Any impression left on a molluscan shell by the attachment of a soft part (e.g., mantle, muscle, or foot).
Axial Pertaining to or more or less parallel to the axis of coiling.
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.
Band A strip of shell material differentiated by color or construction from the shell on either side of it.
Banding Color marking in continuous stripes.
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.
Bivalve bi-valve (L bi=two; valva=door) any mollusc having two valves or shells that are hinged together, as in mussels and clams. more
Body whorl The most recently formed whorl of a spiral shell (generally gastropod but could refer to paragastropod or spiral tergmyan - in cephalopoda the term "living chamber" is more usually used), terminating in the aperture.
Branchiae(Gr Branchia=gills) gills; respiratory organs for breathing the oxygen dissolved in water.
Branchial (GR branchia=gills) The ventral or inhalant aperture. Used to take in food particles and oxygen and to release fertilized eggs.
Buccal buc’cal (L bucca=the cheek) pertaining to the mouth or cheek
Buccal mass a bulging; tongue-like object, made up of cartilage and muscle, which supports the radula
Buttress A shell-strengthening structure--e.g., a supporting laminar costa in gastropods, or a support for part of the hinge in bivalves.
Calcareous cal-ca’re-ous (L calyx=lime) consisting of, containing, or by the nature of limestone or calcium carbonate; a shelly substance.
Cephalic ceph-al’ic (Gr Kephale=head) of, pertaining to, on, in, or near the head
Calcified With the conchiolin matrix partially or entirely reinforced by calcium carbonate intercalations.
Cephalopoda Ceph-a-lop’o-da (Gr Kaphale=head; pous=foot) One of the seven classes of molluscs. (Squids, octopus, Argonaut, Spirula.) more
Ceras cer’as (Gr Keras=horn) a horn or horn like appendage located on nudibranchs
Chambered cham’bered (Gr Kamara=anything with an arched cover) having divisions across the hollow of the shell, separating or dividing the same into chambers. (as in the Nautilus)
Chiton chi’ton (Gr Chiton=tunic) the coat-of-mail shells (Polyplacophora) . They possess a shell made up of eight shell plates. more
Cilium (plural Cilia) (L cilium=eyelid) A hair-like extension from the cell surface and capable of rhythmic movement. Used to designate the filaments on the mantle, in the gills, etc.
Coelom coe’lom (Gr Koilos=a hollow) body cavity, that space between the viscera and the body wall.
Columella col-u-mel’la (L columen=column) The thickened axial pillar around which the whorls of univalves are built.
Comarginal parallel with the margin
Compressed - high and narrow in cross-section, flattened laterally
Conchiolin con-chi’ol-in (L concha=shell) proteinaceous organic compound forming the periostracum of a shell, and also forms the organic matrix for calcareous parts of the shell.
Conchologist One who collects shells; a student of conchology.
Conchology con-chol’o-gy (L concha=shell) The study of marine, fresh-water and land-shells; the arrangement and description of molluscs based upon a study of the hard parts only. Now generally replaced by Malacology..
Convolute With last whorl completely concealing the earlier ones.
Cord(s) Coarse, rounded spiral or transverse linear sculpture on the shell surface; smaller than costae.
Cordate Heart shaped.
Corneous Consisting of horn, of a non-calcareous hornlike texture, as the opercula of some mollusks, such as the Neogastropod Busycon.
Corrugated Folded or ridged; broadly and heavily sculptured.
Costa (pl. costae) Large, cordlike ridge that runs longitudinally, spirally, or concentrically on a shell rib. Line of ornament similar to, but of greater prominence than, a cord.
Costate Rib-like sculpture, which is strongly ridged.
Cotype One of several specimens collectively designated type; no longer used. See Holotype and Paratype.
Crassate Coarse and solid.
Crenate, Crenulate or Crenulated Finely notched, scalloped, wrinkled or delicately corrugated around the margin. Describing edge of the inner margins of some bivalve shells, or the outer lip margin of gastropod shells.
Crenules Small notches or beads.
Crop (AS cropp=craw) a widened part of the esophagus where food may be temporarily stored before being passed on to the stomach
Ctenidium cten-id’I-um (Gr Kteis=comb) a gill-comb. Molluscan gill ; one of the respiratory organs found in molluscs. Plural is ctenidia
Cusp Point of a tooth. A prominence, or point; temporary ridges of sand perpendicular to the shoreline.
Decussate or Decussated Sculpture crossings at acute angles. Having a latticed surface ornamentation formed by the intersection of fine ribs, not necessarily at right angles. See also Cancellate.
Deltoidal More or less triangular.
Dentate Sculptured, with teeth or short ridges. Having conspicuous projections along a margin in gastropod shells. See Denticles.
Denticles Small teeth. Small projections around the margin of a gastropod aperture or the margin of a bivalve valve, especially near the hinge. (Not to be confused with true interlocking hinge teeth.)
Denticulate(d) Sculptured with small nodules or points. Having denticles. Toothed.
Dentition Tooth structure: referring in bivalves to the hinge teeth, in gastropods usually to the elements of the radula.
Depressed Low in proportion to diameter.
Detritus de-tri’tus (L detritus=a rubbing away) a mass of disintegrated material composed of bits of sea weed and other organic wastes found on the ocean floor
Deviate de’vi-ate (L de=from; via=away) To turn aside from the straight or regular coarse.
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.
Dioecious di-oe’cious (Gr Di=two; oikos=house) having the male and female present in different individuals. ( an individual is either male or female but never both). Opposed to monoecious
Discoid or Discoidal Disc-shaped; whorls coiled in one plane more or less compressed.
Distal dis’tal (L di=apart; sto=stand) relatively remote from the center of the body or point of attachment. Away from the center of origin, the farthest part from an object.
Dorsal dor’sal (L dorsum=the back) referring to the back edge or top of a bivalve, in the region of the hinge. The back of a gastropod remote from the aperture; The conical top surface of a limpet
Ectoderm - in triploblastic (three-layered) animals, this is the outer body layer. It forms the skin, nervous system, etc
Egg capsule A protective structure enclosing an individual egg or a cluster of eggs.
Elevated Raised up; high in proportion to diameter.
Elongate Extended; considerably longer in one dimension than another.
Emarginate With margin, or edge, of shell cut into by a notch or notches or gently indented.
Endogastric - coiled in a ventral or posterior direction. The opposite of Exogastric. Helcionelloids, early cephalopods (Plectronoceras, etc) and gastropods and all endogastrically coiled, although the latter developed from exogastric ancestors by means of torsion. illustration.
Epidermis The outermost layer of the molluscan body, not associated with the shell; cuticle; integument or skin. (Often erroneously applied to the periostracum, the outer layer of the shell.)
Epifauna Animals that normally live exposed, above the substratum surface; may be with or without attachment.
Esophagus e-soph’a-gus (Gr Oisophagos= the gullet) A membranous tube or canal through which masticated food or drink passes from the pharynx to the stomach
Exhalent siphon a short outlet formed of a fold of mantle through which water and other wastes are expelled.
Exogastric - coiled in a dorsal or anterior direction. The most primitive conchifran molluscs are exogastric.
Flange An erect, projecting flattened ridge.
Foliaceous Leaf-like, flattened, projecting like tiles.
Foot The muscular locomotor organ, undersurface of the body of a mollusc upon which the animal rests or moves. In bivalves, the contraction and expansion of this organ is used in the burrowing, locomotion, or for anchoring the animal. In the cephalopods, it is represented by the siphon and possibly the tentacles. The presence of a creeping or muscular foot is one of the characteristics that distinguish molluscs from other organisms.
Frilled With a series of crowded, fine, wavy or pleated, sharp, often scaly ridges.
Gaping Incapable of closing completely.
Gastropoda gas’trop’o-da (Gr Gaster-stomach; pous=foot) A class of molluscs. Scientific term for molluscs which have undergone torsion. The name refers to the fact that these creatures seem to creep upon their bellies. In fact in gastropods the stomach is situated well above the region of the foot. more
Gill (ME gile=a gill) or Ctenidium. A large sheet-like organ used for breathing the air dissolved in the water. In bivalves they also play the role of food collecting. The respiratory organ of molluscs.
Girdle gir’dle (AS gyrdel=a girdle) A flexible, leathery, muscular integument holding the valves of chitons in place. It is often ornamented with scales, spicules, or hairy processes.
Globose Roughly spherical in outline.
Globular Globe or sphere-shaped, like a ball.
Gonad gon’ad (Gr Gonos=seed) A generative tissue which eventually becomes a testis or ovary. Gonoduct, an oviduct or seminal duct.
Granular Bearing granules as surface sculpture.
Granulate, Granulated or Granulose Finely beaded or noduled. Having a rough surface of grainlike elevations.
Granule A pustular surface structure.
Groove An elongate and fairly uniform depression in the shell or soft parts of a mollusk.
Growth line(s) Impressed lines on the shell-surface due to growth-stages and rest periods.
Growth stages Exaggerated growth lines indicating a cessation of growth.
Head In general, the area of a molluscan body that bears the sense organs and the mouth (or proboscis). A usually distinct structure located at the animal's front end, containing the mouth, eyes, and sensory tentacles; absent in bivalves, poorly defined in chitons.
Haemolymph he’mo-lymph (Gr haima=blood) Molluscan blood
Helical Spirally coiled.
Hermaphrodite her-maph’ro-dite (Gr Myth=Hermaphrodites, having a fabled son of Hermes and Aphrodite) Having the sexes united in the same individual The animal is both male and female.
Holotype hol’o-type (Gr Holos=whole = type) The original type. The single specimen upon which a species is based
Impressed Indented. Pushed down, either as a line or an area.
Incised Sculptured with one or more sharply cut grooves.
Incremental lines Faint concentric growth lines.
Incrustation An irregular deposit on the shell surface.
Incurved Term used to indicate that a structure curves in upon itself, as do the umbones of certain bivalves, or the spines or lamellae of certain bivalves and gastropods.
Infauna, infaunal Sessile and mobile animals that spend part or all of their lives buried beneath the substratum. Many bivalves are infaunal. Compare with semi-infaunal
Inflated Applied to rotund shells of thin structure; swollen, increased unduly, distended.
Inflected or Inflexed Turned inward, in the same direction.
Inhalant siphon a tube like fold of the mantle along which water, containing oxygen and food particles is drawn into the mantle cavity.
Intercostal Placed or occurring between the ribs.
Intermediate ribs Secondary sculpture, smaller than the primary ribs.
Involute In gastropods (e.g., cypraea), coiling so that later whorls (or just the final whorl) envelop earlier whorls, such that the height of the aperture is the greatest vertical dimension.
Iridescent Colors resulting from light refraction, not pigmentation.
Iteration, Iterative morphogenesis. In computer science, performing a repeated mathematical operation on a resulting value. In this context the term is used to denote processes that result in both metameric segments and repeated ectodermal skeletal structures.
Labial Palps la’bi-al palps (L. labium=lip palpare=to feel) Paired ciliated triangular flaps on either side of the mouth in bivalves.
Lamellar gills la-mel’lar gills (L. lamella=small plate) Enlarged, flattened plate-like gills (ctenidia) which form the feeding organs of most bivalves.
Lamellibranchia Alternative name for Bivalvia; Bivalvia preferred.
Larva The youngest stage of a mollusk after it hatches from the egg.
Larval shell Shell of a molluscan larva before it undergoes metamorphosis, usually set off by a change of sculpture.
Lateral lat’er-al (L latus=the side0 pertaining to the side.
Lateral teeth interlocking teeth of bivalves, not functioning as a hinge but serving to prevent valves from sliding upon each other when closed.
Length In bivalves, the greatest horizontal dimension parallel to a line bisecting the adductor scars; in gastropods and scaphopods, the same dimension as height; in chitons, the greatest dimension parallel to axis of symmetry; in cephalopods, variously defined, but generally taken as the greatest dimension of the animal when the arms are stretched out parallel to their full extent.
Malacologist One who studies the mollusc animal along with the shell.
Malacology mal-a-col’ogy (Gr malos=soft-bodied logia=to speak) The study of molluscs (clams and snail) based on soft anatomy. The branch of zoology that deals with molluscs, the animal within the shell.
Malacozoology The study of living mollusks in relation to their animate and inanimate environment.
Mantle man’tle (L mantellum=a cloak, mantle) A soft, fleshy sheet of tissue that surrounds the mollusk's body and lines the inner surface of the shell. It secretes the materials that form the shell from the marginal glands and provides the periostracum. The presence of a mantle is one of the characteristics that distinguish molluscs from other organisms.
Mantle line The line on the dorsal surface of a cowry shell and some bellerophontids where the mantle lobes meet.
Margin Extreme edge of valve of bivalve shell; also the thickened periphery of base of some gastropods, notably cowries; sometimes used as equivalent to edge.
Median Along the central line or axis.
Metamery, Metameric - having a series of repeated similar body segments - e.g. an annelid or arthropod. See also Pseudometamery
Muscle scar Slight depression on the inner surface of the valve of a bivalve shell where a muscle is attached; in limpets, the scar left by the margin of the mantle and the foot retractor muscles. See also Accessory Scar; Adductor scar.
Nacre na’cre (Fr nacre=mothe-of-pearl) The pearly or iridescent substance which lines the interior of some molluscs shells.
Nacreous With a layer of nacre, or mother-of-pearl.
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.
Nephridium ne-phrid’I-um (Gr nephros= a kidney) one of the tubular renal organs of the molluscs.
Nephridiopore; the duct through which liquid wastes drain from the nephridium.
Operculum o-per’cu-lum (L operire=to close or shut) 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 molluscs.
Operculate; having an operculum
Opisthogyrate In bivalves, having the beaks pointed backward, or posteriorly; opposite of prosogyrate.
Orbicular Circular or rounded. Order: A group of related superfamilies.
Ornament Surface sculpture standing out in relief on shell surface.
Osphradium os-phr’di-um (Gr Osphraddion=strong scent) An olfactory organ of some molluscs. A collection of elongated sensory cells over each gill.
Palps (plural palpi) (L palpare=to feel) Ciliated structures that surround the mouth. Food is sorted here and moved towards the mouth.
Pelagic pe-lag’ic (Gr Pelagos=the open sea) Pertaining to or living in the open sea far from land.
Pelecypoda pel-e-cyp’oda (Gr Pelekys=axe; pous=foot) Another term for Bivalves. Molluscs bearing a two valved shell that is hinged along one edge.
Periostracum per-I-os’tra-cum (Gr peri=around; ostracukon=shell) The outer skin or horny covering on the exterior of many shells. May be thin and transparent or thick, fibrous or hairy.
Planispiral Coiled in a single plane. Bellerophontiform and cephalopod shells are mostly planispiral
Planktotrophic Refers to planktonic larval development where the larvae feeds on micro-organisms and development time in the plankton is long.
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.
Porcellaineous Polished; surface and texture as in porcelain.
Posterior The rear or tail end of an animal.
Propodium pro-po’di-um (Gr Pro=before; pous=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 of a univalve. 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. The rudimentary or embryonic shell of a bivalve is called a Prodissoconch.
Pseudometamery - having multiple body organs, repeated in a metameruic fashion, but the organism as a whole is not metameric - e.g. Trybliida, Polyplacophora. There may be a gradation between pseudometamery and full metamery. Sometimes pseudometamery and metamery are taken to mean the same thing - e.g. in discussions of primitive molluscs.
Radial lines Radiating in relatively unbroken lines from the beaks of bivalves, the apex of gastropods, or the mucro of chitons, as contrasted with concentric.
Radiating Spreading in various directions
Radula rad’u-la (Lrado=to scrape or scratch) 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. The presence of a radula is one of the characteristics that distinguish molluscs from other organisms.
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.
Rugae folds; wrinkles; ridges in the ornament of a shell
Scaphopoda sca-phop’o-da (Gr Scaphe=boat; podos=foot) 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. more
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. Synonymous with ornament.
Selenizone Spiral band of crescentic growth lines, associated with marginal slit or foramen in certain univalves.
Semi-infaunal - lying partially buried in sediment, sand or mud. Some bivalves are semi-infaunal. Compare with infaunal
Shell (AS scell=shell) A hard rigid, calcareous or chitinous structure encasing an animal, or covering some part of it. Some molluscs have an internal shell.
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 as in the pallial line of a bivalve or gastropod.
Siphon si’phon (Gr Siphon=siphon) A prolongation or fold of the mantle conveying water into or out of the mantle cavity of most molluscs.
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.
Siphuncle si’phun-cle (L siphunculus=a little tube) The small tube connecting the chambers in a nautilus shell.
Slit (AS slite=slit0 A shallow or relatively long incision in the outer margin of the aperture of a gastropod.
Spicule spic’ule (L spiculum=a dart) A small, slender, hard body, sharp-pointed, often needle-like as the spiculous fringe found on the girdle of chitons.
Spiral sculpture Sculpture following the helical growth of a gastropod shell.
Spire All whorls of a spiral shell exclusive of the body whorl.
Striate Marked with striae.
Suture The continuous spiral line of junction of whorls of a gastropod shell. The septal connecting in cephalopods
Symmetrical sym-met’ric-al (Gr syn=with; metron=measure) Equal-sided, well balanced, having similar parts arranged in regular reverse order on both sides.
Thread A very fine sculptural element of a shell, raised above the surrounding surface. Finer than a rib.
Trema (p. tremata) perforation of a shell, generally formed by periodic closure of a slit, but occurring also at the apex of some fissurulid limpets
Trochoid or Trochoidal Like an inverted spinning top, or like the shell of a Trochus having a pointed spire, flat sides and flat base.
Truncate Abruptly cut off; applied to the square-ended appearance of certain bivalve shells, and to the abrupt termination of the columella in some gastropod shells such as Planaxis.
Tubercle(s) Elevated knob-like projections or protrusion; larger than pustule.
Truncate Cut off at the end, blunt.
Umbilicate Navel-like; with depressed cavity. Having an umbilicus.
Undulate Having a wavy surface.
Untorted - a mollusc, e.g. a gastropod predecessor, that has not undergone torsion
Valve (L valva=a leaf of a door) 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. hence Univalve; one a single piece shell Bivalve; a two-pieced shell. Multivalve: more than two shell plates as in the chitons.
Veliger vel'I-ger (L veliger=snail-bearing) a larval mollusc in the stage of development where it has developed ciliated swimming membrane or membranes.
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 apertural surface of a gastropod shell; the edge remote from the hinge in a bivalve; the ventral margin is opposite the umbones. Opposite to dorsal.
Vermiform Like a worm in shape.
(from Man and Mollusc Glossary)
AS
= Anglo-Saxon
Fr = French
Gr = Greek
L = Latin
Glossary/Mollusks - a very comprehensive glossary; Man and Mollusc Glossary - includes derivation of original word
| Phylogeny |
page by M. Alan Kazlev, checked ATW050713
page uploaded 28 December 2002