Aperture the opening at the front of the gastropod shell, from which the foot and head of the animal protrude.
Apical organ An organ sensitive to gravity, located at the end opposite the mouth in a ctenophore; consisting of a capsule containing granules that tumble in response to gravity as the animal's position changes, causing the animal to right itself.
Abdomen the hindmost division an animal's body
Abductor muscle In bivalve mollusks, a muscle that draws the two valves together, enclosing the soft parts
Ambulacral groove A groove containing rows of tube feet on the lower surface of a sea star or a brittle starfish
annelids also known as the segmented worms, are a large phylum, with over 22,000 extant species including ragworms, earthworms, and leeches. The species exist in and have adapted to various ecologies – some in marine environments as distinct as tidal zones and hydrothermal vents, others in fresh water, and yet others in moist terrestrial environments.
Antenna A sensory appendage on the head of an arthropod or annelid
Anterior the forward end of a bivalve shell
Apex beginning of the shell growth, the top of the gastropod spire
Apophysis a projecting spur inside a bivalve shell below the umbo, the site of a muscle attachment.
Axis the straight line with respect to which a body (shell) is symmetrical. Often referred to as the central structure of spiral shell
Aristotle's lantern The chewing mechanism of a sea urchin. It has 5 teeth operated by a complex system of levers and muscles
Base In gastropods, the portion of the body whorl below the periphery at the bottom of the shell
Basal Callus In olive shells, a shelly spirally-ridged thickening on the columellar base.
Beak The initial or earliest, part of a bivalve shell.
Biconic Tapering at both ends, like two cones placed with their broad ends together.
Bilateral symmetry When the left side is an exact counterpart of the right
Binary Fission A mode of asexual reproduction in which the body of an organism divides into two equal parts
Bioluminescence Light produced by a living organism through a biochemical reaction
Bivalve A shell with 2 valves or shell parts
Body Whorl In gastropod shells, the final whorl, and usually the largest, containing most of the animal's (mollusk's) soft parts
Brackish Containing some salt, but less than seawater
Budding A mode of asexual reproduction in which an outgrowth of an organism develops and forms a new individual
Byssus A bunch of silky threads anchoring some bivalves to solid objects
Byssal gap In some bivalves, the opening between the margins of the valves through which the byssus passes
Byssal notch In scallops and wing shells, a triangular or rounded indentation through which the byssus emerges
Calcareous Composed of calcium carbonate
Callum Thin calcareous covering of the gape in some clams
Callus A thick or thin layer of shelly substance generally smooth and glossy and sometimes transparent
Canal A channel at the top or bottom (rear or front end) of the aperture to accommodate the siphon of a gastropod
Cancellate Longitudinal and spiral lines or ribs, crossing.
Carnivorous feeding on the flesh or of other animals (meat eaters)
Cardinal Tooth A projection on the hinge plate below the umbo
Cartilage An internal , elastic substance found in bivalves, which controls the opening of the valves(shell)
Ctenophora They comprise a phylum of marine invertebrates, commonly known as comb jellies, that inhabit sea waters worldwide. They are notable for the groups of cilia they use for swimming (commonly referred to as "combs"), and they are the largest animals to swim with the help of cilia. Depending on the species, adult ctenophores range from a few inches to 5 feet in size.
Their bodies consist of a mass of jelly, with a layer two cells thick on the outside, and another lining the internal cavity. The phylum has a wide range of body forms, including the egg-shaped cydippids with a pair of retractable tentacles that capture prey, they genrally prey on other ctenophores.
Central Teeth In bivalves the hinge teeth located on the interior under the umbones (same as cardinal tooth)
Chondrophore A spoon like projection in the hinge of some bivalve shells
Cnidaria is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments (predominantly the latter), including jellyfish, hydroids, sea anemone, corals and some of the smallest marine parasites. Their distinguishing feature is the cnidocytes, specialized cells with ejectable flagella used mainly for envenomation and capturing prey. Their bodies consist of mesoglea, a non-living jelly-like substance, sandwiched between two layers of epithelium that are mostly one cell thick.
Cnidarians mostly have two basic body forms: swimming medusae and sessile polyps, both of which are radially symmetrical with mouths surrounded by tentacles that bear cnidocytes. Both forms have a single orifice and body cavity that are used for digestion and respiration. Many cnidarian species produce colonies that are single organisms composed of medusa-like or polyp-like zooids, or both (hence they are trimorphic).
(REF: "cnidaria". Oxford English Dictionary (Online ed.)) (REF: "WoRMS - World Register of Marine Species" )
Columella The pillar of a gastropod shell around which the whorls form their spiral circuit
Concentric In bivalves, refers to the curved ridges on the shell, being arcs with the beaks at the center
Conchologist A student of mollusks and their shells
Conic Shaped like a cone
Crenulate Notched or scalloped
Cuspidate Prickly pointed
Deck A small platform under the beaks or diaphragm
Decussated Lines crossing at right angles
Denticle A small usually rounded tooth
Detritus Fine particles of plant, animal or inorganic matter
Dextral Turning from left to right; right-handed.
Diatom A microscopic, unicellular plant living either attached to a solid or as plankton, and capable of photosynthesis
Dinoflagellate A microscopic, unicellular, planktonic organism with two flagella, sometimes capable of photosynthesis
Diocious Having separate sexes
Discoidal The whorls being coiled in one plane
Dorsal Belonging to the back
Drift line A line of debris left by waves at the high-tide line
Ears In scallops and file shells, triangular or oblong projections at the ends of the hinge line.
Ectoderm The outermost layer in developing embryos, lying over the mesoderm and the endoderm.
Egg Capsule a protective structure enclosing an individual egg or a cluster of eggs.
Echinoderms. This is a marine group of animals which include sea stars, brittle stars, sea urchins, sea cucumbers and sea lilies. The echinoderm's most common feature is their radial symmetry. The body is usually arranged in five parts. This is the body axis, with the mouth at one end and the anus at the other. Some species have their mouth facing up, while others down.
The Echinoderm have an internal limy skeleton, covered by skin. Some species have spines and some spines are moveable and others fixed. spines can vary in size and shape.
phylum is an internal hydraulic system, termed the water vascular system. This system operates many tube feet called pedia. The feet are slender, fingerlike appendages, arranged in rows. These the animal extends by pumping full of fluid and then retracts its muscles within the tube foot. The tube feet are used to aid in movement and feeding. Some animals have suction disks at their tips. This allows the animal to cling to objects.
Inside the echinoderms body is a complex system of canals, filled with sea water. The water passes thru a sieve plate as it enters and exists the body.
The echinoderm has a complex digestive system, nervous system and reproductive organs. Body waist goes thru the skin or the water vascular system.
Endoderm The innermost layer in the developing embryo lying beneath the ectoderm and the mesoderm.
Epidermis The outermost cellular layer of skin
Epithelio Muscular Cell In cnidarians, an epidermal cell with long, contractile fibers on its inner surface, lying parallel to the surface of the body.
Escutcheon A depression found behind the umbones of a bivalve shell, often encompassing an external ligament
Equivalve Both valves (upper and lower shell of a bivalve mollusk) have the same size and shape
Family A unit containing two or more closely related species belonging to one genus or two or more geneta, subordinate to a super family.
Fauna The animal life of a region or locality
Fissure A slit or cut
Flagellum (flagella) A whip/like appendage of a cell used in locomotion or in creating a current.
Flange An erect, projecting flat ridge.
Fluted a series of elongated, slightly projecting channels and ridges along a margin. Scalloped or arched
Foot A muscular organ used in moving, adhering to a surface, or digging into sand and mud, by gastropod mollusks
Frilled a series of crowded, fine, wavy or pleated, sharp, often scaly ridges.
Furrows Broad, usually shallow grooves
Fusiform Spindle shaped
Gape A region of incomplete closure between the two valves of a bivalve mollusk
Gastropod Stomach footed. A mollusk with head bearing tentacles and eyes, a foot, and a one piece shell (sometimes with no shell) A snail or slug
Gastrodermis The cellular layer lining the digestive cavity
Gemmule An internal bud of certain sponges consisting of a mass of cells surrounded by a tough sheath, which survives the winter or other rigors, and germinates to form a new individual under more favorable conditions.
Genus (genera) A unit containing one or more species that share many structural features and ecological characteristics and whose scientific names all begin with the same word; subordinate to a family.
Gill A respiratory organ that extracts dissolved oxygen and salts from the water
Gill Chamber In bivalves it is the space between and around the the gills
Girdle The muscular ribbon surrounding and binding together a chiton's shelly places
Globose Tending to be inflated, like a ball
Granulose surface covered with small raised pimples
Gonad Sex gland, ovary or testis
Growth Line or Ridge In gastropods and bivalves, A fine or coarse raised line, defining a temporary pause in the shell growth
Head A usually distinct structure located at the animal's front end, containing the mouth, eyes, and sensory tentacles. This is absent in bivalves and poorly defined in chiton shells
Head valve The valve at the front end of a chiton that laps over the front edge of the next valve
Herbivorous Feeding on algae or other plant material
Hermaphroditic Combining the organs and functions of both sexes
Hinge Inner edge of the valve of a bivalve shell, mostly joined by a ligament to the opposite valve and usually bearing teeth in that valve.
Hinge Line In bivalves it is the area along the upper margin where the two valves are hinged
Hinge Teeth In Bivalves, a series of teeth along the valves' upper margins that interlock. This helps keep the valves aligned
Holdfasts Finger/like extensions at the base of seaweeds, such as kelp, that serve to attach the plants to rocks or other objects
Horny Made of horn, a brown fibrous organic substance
Impressed Indented or sunken
Incised Finley scratched.
Incurved Turned inward
Inequivalve Valves differing in shape or size
Inner lip In coiled gastropods, the aperture's inner margin, which usually consists of the parietal and columellar walls. The portion of aperture adjacent to the axis or pillar
Insertion plates In chitons, shelly extentions of the valves' edges the project into the girdle.
Intermediate valves In chitons, the 6 valves between the head and tail valves.
Intertidal Area between the high and low tide lines
Involute Rolled inward from each side as in a cypraea shell species.
Iridescent Reflecting rainbow colors.
Jaws In most gastropods, a pair of horny structures within the pharynx that aid in the breaking up of food particles
Keel A more or less sharp edge, flattened ridge, usually at shoulder or periphery
Lamellibranchia another name for bivalves
Lanceolate Shaped like a lance.
Larva Youngest stage of the mollusk after it hatches from the egg
Ligament In bivalves, a horny elastic structure located on the exterior or interior of the shell's hinge line, connecting the valves; which arcs to keep the valves open.
Ligament area In some bivalves, the area between the umbones containing the external ligament.
Ligament cleft or pit A narrow depression behind the umbones in which the ligament may lie.
Ligament shelf A shelly internal or external platform on which the ligament lies.
Linear Very narrow
Lineated Marked with lines.
Lips The margins of the aperture.
Littoral zone The area between the high and low tide lines, (intertidal zone).
Lirate Resembling fine incised lines
Lunule In some bivalves, a heart shaped or elongate depression in front of the umbones
Lyrate Shaped like a lyre.
Malacology The scientific study of mollusks
Mandible The jaw, the cutting or grinding mouthpart found in certain arthropods and annelids.
Mantle A fleshy lobe which secretes the mollusk's shell and lines the inside of the shell wall
Mantle cavity The space enclosed by the mantle of mollusks containing the gills and the visceral mass.
Mantle folds In bivalves, the two extensions from the mantle that lie against each valve and enclose the internal organs.
Mantle lobes In some gastropods, extensions from the mantle that extend partly or entirely over the shell.
Manubrium Fleshy stalk on the underside of a cnidarian medusa, bearing the mouth.
Margin The shell edge.
Masculate Splashed or spotted
Maxilla The mouth part on a crustacean located directly behind the mandible.
Maxilliped The thoracic appendage of a crustacean modified as an auxiliary mouth part.
Measurement of shells There are two types of measurements. One, point to point or the greatest distance between two points on a shell, this may be the shell width, length or height. The second is the surface of the shell. This type of measuring takes into account shells are usually not flat but have a curvature, especially bivales. Most measurements in our shell description are surface measurements. Surface measurements can and generally do differ from point to point.
Medusa One of the body forms of a cnidarian, Cup shaped or bowl shaped with a mouth on a stalk on the underside, and capable of swimming by rhythmic contractions.
Mesentery A membrane suspending an organ in the body cavity of an animal, its surface continuous with both the surface of the organ and the lining of the cavity.
Mesoderm The middle layer in a developing embryo, lying between the ectoderm and the endoderm.
Mesoglea The jelly like layer between the epidermis and gastrodermis in a cnidarian.
Mesoplax An accessory plate.
Middle area In chitons, the triangular area on a valve between the narrow central area and the side area.
Mollusk A soft-bodied, legless, invertebrate animal which usually secretes calcareous shell
Mother of Pearl A shelly layer or the inner lining of a shell displaying a pearly (nacreous)surface.
Mucus Slippery protective substance secreted onto the exposed surfaces of many animals.
Muscle Scar The impression inside the valve of a bivalve shell made by an adductor muscle (muscle holding the valves together).
Mutualism An intimate relationship between organisms of two different species in which both gain from the association
Nacreous (Nacre) Pearly. Mother of Pearl.
Nematocyst In cnidarians, an explosive capsule in a cell that erupts when stimulated, extending along, stinging or entangling thread.
Nephridium (nephridia) An excretory organ or kidney in some invertebrates
Nodose Having tubercles or knobs.
Node A lumpy protuberance, smaller than a tubercle
Nodule Knoblike projection.
Nucleus The initial or nuclear whorl. Earliest part of a gastropod shell
Nymph The narrow ledge on the hinge behind the umbo, to which the external ligament is attached.
Oblique in a slanting direction.
Obsolete Ceasing to exist, no longer present.
Ocellus (ocelli) An eye-spot; a simple photoreceptor capable of distinguishing a source and change of light intensity, but not of forming an image.
Ornament Raised or depressed features on the shell surface.
Operculum A lid attached to the gastropods foot that closes the shell's aperture, found in many gastropods (snails) and in some tube dwelling annelid worms.
Opisthosoma The body region to the rear of the prosoma in some arthropods.
Oral Arm One of the appendages surrounding the mouth of a scyphozoan medusa.
Oral Disk The flat area around the mouth of an anthozoan polyp.
Oral Lobe A conical, rounded or squarish structure lying above and in front of the mouth of an annelid worm; the prostomium.
Orbicular Round or circular
Osculum (Oscula) The excurrent pore of a sponge.
Ostium (ostia) One of the incurrent pores of a sponge through which water enteres the animal.
Outer Lip In coiled gastropods, the outer edge of the aperture. It is the most distant from the columella
Ovate Egg shaped or oval.
Oviparous Egg laying; a term applied to animals that release eggs from the body of the female before undergoing embryonic development.
Pallets In shipworms, a pair of paddle-shaped or plume like structures at the clam's hind end that help close off the burrow in which the animal lives.
Pallial Relevant to the mantle.
Pallial Line An impressed line inside the valve of a bivalve shell parallel to the margin, which marks the position of the mantle edge.
Palp An appendage, usually sensitive to touch or taste, located near the mouth of an invertebrate
Papilla (pl. papillae) A nipple/like projection or part.
Parapodium (pl. parapodia) One of the paired appendages on the segments of a ploychaete annelid.
Parasitic Living in or on another animal and deriving food from it.
Parenchyma Undifferentiated tissue filling the space not occupied by organs in the body of a flatworm or nemertean worm.
Parietal Describes that part of the inner lip of a gastropod shell behind the columella.
Parietal Callus In gastropods, a shelly thickening or deposit on the parietal wall.
Parietal Wall In gastropods, the portion of the body whorl bordering the upper part of the aperture opposite the outer lip.
Pedal Disk The flat base of a sea anemone, by which it adheres to a solid surface.
Pedal Laceration In sea anemones, a mode of asexual reproduction in which a bit of tissue separates from the base as the animal creeps along and grows into a complete animal.
Pedicellaria (pl. pedicellariae) A small pincher/like or vise/like structure on the surface of a sea star (star fish) or sea urchin, used to keep the body surface clear of other organisms.
Pelagic Living in the open sea.
Penultimate Whorl Next to the last whorl.
Periostracum The external smooth, often fibrous and horny coating of corneous material covering many shells when fresh
Periphery In gastropods, the widest part of a whorl.
Peristome Edge of the aperture.
Pharyngeal Pertaining to the pharynx.
Pharynx The part of the digestive tube between the mouth cavity and the stomach or the esophagus.
Photosynthesis The process by which plant cells use light energy to produce organic compounds from carbon dioxide and water, catalyzed by the green pigment chlorophyll, with free oxygen as by/product.
Pincer A term used to designate the nipper/like appendage of crustaceans, the chela.
Pincher The nipper/like appendage of some bryozoans or echinoderms whose function is to keep the surface free of other settling organisms, also called an avicularium in the bryozoans, and a pedicellaria in the echinoderms; a mouth/part in sea spiders.
Pinnate Feather/like with two rows of simple branches rising in one plane from the opposite sides of an axis.
Pipe A small tube protruding from the rear end of some tusk shells
Plankton A collective term for all organisms living suspended in water, either unable to swim or swimming so feebly as to be at the mercy of water currents.
Planula (pl. planulae) The larva of a cnidarian, usually rod/shaped, with a ciliated epidermas surrounding a solid inner mass of cells.
Pleat Applied to folds on the columella.
Plicate Folded or pleated.
Plug The shelly infilling at the rear end of a tusk shell tube.
Polyp One of the body forms of a cnidarian usually cylindrical with a mouth surrounded by tentacles at one end and with the other end attached.
Porcelaneous resembling porcelain; white, shiny but not pearly, not porous.
Posterior The backward end of a bivalve shell.
Primary Consumer A species that feeds directly upon primary producers; example herbivore.
primary Producer An animal capable of food synthesis, usually photosynthesis, from inorganic compounds.
Proboscis In some mollusks, a tubular extension of the head, with the mouth at the end.
Protoconch The initial whorl of a snail shell.
Prosoma The front/most body division of some arthropods.
Prostomium A lobed segment anterior to the mouth in an annelid worm.
protozoan A one-celled animal belonging to the phylum protozoa.
Pustule A small, rounded protuberance, smaller than a node.
Pygidium The terminal segment of an annelid's body, bearing the anus.
Pyriform Pear shaped.
Radial. It describes the direction of the raised or depressed ornamental feature on a bivalve, running from the umbo toward the edge of the valve.
Radial Canal. A canal branching from the central digestive cavity of a medusa and extending to the margin of the bell.
Radial Symmetry. A body plan in which repeated body parts are arranged around a central point, as in a wheel.
Radula. An organ located in the mouth cavity and consisting of very small teeth, either on a flexible muscular ribbon or unattached. These are used by snails, chitons, tusk shells and cephalopods in feeding.
Ramp. A broad, flat topped ledge below the suture of a wheel.
Range. The total distribution of a species.
Ray The arm or radiating appendage of an echinoderm.
Recurved. Curving upward or downward.
Resilium. Internal cartilage in a bivalve hinge; causes the shell to spring open when the muscles relax.
Reticulate. crossed like network.
Ribs. Ridgelike sculptural elements. In gastropods it is the axial and in bivalves, the radial.
Riblets. Small ribs. The continuous elevation of the shell surface.
Rostrum. A beak.
Rubble. A dense accumulation of broken shells, coral fragments and stones on the sea floor.
Rugose. rough or wrinkled.
Scale. Raised sharp edged, ornamental feature, sometimes fluted.
Scalariform. loosely coiled.
Salinity. The salt concentration of a solution. Salinity of seawater is expressed in parts per thousand instead of percent. Average salinity of seawater is 35 parts per thousand.
Sargassum weed. A brown algae found on the open ocean, especially in the Atlantic.
Scalloped. Bordered by a series of equal semicircular or angled projections.
Scavenger. An animal that feeds on refuse or dead and decaying animal and plant material.
Scientific Classification. In biology, taxonomy means arrangement it is the scientific study of naming, defining and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon) and these groups are given a taxonomic rank; groups of a given rank can be aggregated to form a more inclusive group of higher rank, thus creating a taxonomic hierarchy. The principal ranks in modern use are domain, kingdom, phylum (division is sometimes used in botany in place of phylum), class, order, family, genus, and species. The Swedish botanist Carl Linnaeus is regarded as the founder of the current system of taxonomy, as he developed a ranked system known as Linnaean Taxonomy for categorizing organisms and binomial nomenclature for naming organisms With advances in the theory, data and analytical technology of biological systematics, the Linnaean system has transformed into a system of modern biological classification intended to reflect the evolutionary relationships among organisms, both living and extinct.
Sculpture. ornamentation, impressed or raised markings or the shell's surface.
Scyphistoma. In scyphozoans, a polyp stage that buds off medusae by dividing transversely.
Scyphozoa are an exclusively marine class of the phylum Cnidaria, referred to as the true jellyfish (or "true jellies").
(REF: Dawson, Michael N. "The Scyphozoan")
Secondary consumer. An animal that feeds on primary consumers. These are carnivores or parasites.
Segment. One of the serially repeated divisions of the body of an annelid or arthropod.
Semilunar. half moon shaped.
Septum. diaphragm, platform. A sheet or wall of tissue separating two cavities in an animal's body
Serrated. A term applied to the edge of a shells when it exhibits a series of grooves or points.
Sessile. Attached to a substrate; sedentary
Seta/Setae. A bristle or hairlike structure.
Shelf. A thin plate obscuring the aperture of some species of gastropod shells.
Shelf tube. The hallow tube, coiled or not; occupied by most gastropods, all tusk shells and a few bivalves.
Shield. In gastropods, a thickened distinctly margined callus on the body whorl near the inner lip.
Shoulder. In snails, the more or less flattened part of a whorl below the suture.
Side Area. In chitons, the part of an intermediate valve nearest the girdle, separated diagonally from the middle area.
Side Teeth. In bivalves, hinge teeth on either side of the central teeth, at the ends of the hinge area.
Sieve plate. A perforated plate on the surface of an echinoderm through which it can take seawater into or expel the seawater from the water vascular system.
Sinistral. turning from right to left; left handed. In snails, having the aperture on the left hand side of the columella.
Sinuous. Gently waved.
Sinus. a deep cut.
Siphon. The organ through which water enters or leaves the mantle cavity. This opening is frequently tubular, through which an animal takes in or expels water. The siphon carrying water in iks called an incurrent siphon and the siphon carrying out water is called an excurrent siphon. These are found among mollusks and tunicates. The tube is fleshy and retractable
Siphonal band. In olive shells, a broad, flattened spiral band at the shell's base representing former ends of the siphonal canal or notch.
Siphonal canal. In snails, a short channel sometimes tubelike, at the lower end of the aperture through which the siphon protrudes.
Siphonal furrow. In false limpets, a groove on the shell's interior, containing the siphon.
Siphonal notch. In olive shells, the broad opening at the base of the aperture from which the siphon extends; in turrid shells, a notch or shallow embayment on the outer lip from which the anal siphon protrudes.
Siphonal ridge. In certain gastropods, a spiral ridge at the shell's base composed of former ends of the siphonal canal.
Siphonoglyph. A channel in the throat of an anthozoan, through which cilia carry food laden mucus into the digestive cavity.
Slit. A shallow or deep cut in the shell margin or some gastropods and in the umbones of some bivalves.
Species. the subdivision of a genus, distinguished from all others of the genus by certain permanent marks called specific characters. Members are potentially able to interbreed with each other, but are reproductively isolated from other populations.
Spicule. A small structure, often needle like or dartlike, supporting the tissues of various sponges, soft corals and compound tunicates.Spine. A blunt or sharp projection.
Spiral. Winding around a central axis, at right angles to the vertical.
Spiral cord. Sculpture in spiral gastropods that follows the whorls, at right angles to the vertical axis of the shell.
Spire. the upper coiled whorls, from the apex to the body whorl. In gastropods, all whorls above the body whorl.
Spongin. The tough fibrous skeletal meshwork of certain sponges.
Statolith. A heavy granule in a gravity sensing structure; such as the apical organ of a ctenophore.
Stiae. Very fine lines.
Stromboid notch. In winged conchs, a shallow notch on the lower end of the outer lip from which the animal's right eye extends.
Subsutural. Below a suture.
Subtidal. Just below the low tide line.
Super family. An agglomeration of related families.
Suture. In spiral gastropods, the line or space that separates adjoining whorls; where the whorls connect.
Styler. In nemertean worms, a sharp needlelike structure used for puncturing.
Substrate. The surface on which an organism lives.
Sulci. Grooves or furrows.
Suture. The spiral line of the spire, where one whorl touches another.
Swimmerer. One of the small abdominal appendages of a crustacean.
Symbiosis. An intimate biological relationship between two species. This includes parasitium, where one lives at the expense of the other. Commensalism, where the presence of the one neither helps nor damages the other and mutualism, where both gain from the relationship.
Tail fan. A fan like structure at the tip of the tail of some crustaceans, consisting of a telson, or tailpiece and a pair of flattened abdominal appendages.
Tail valve. In chitons, the hindmost valve.
Taxomomy. The science of classifying organisms.
Teeth/Tooth. Pointed or blunt structure(s) inside the outer or inner lip of gastropod shells and on the hinges of bivalve shells
Toothed. With the margin divided into toothlike projections.
Telson. The unpaired terminal structure attached to the last abdominal segment of a horseshoe crab or crustacean.
Tentacle. A long, flexible structure usually on the head or around the mouth of an invertebrate; used for grasping and feeding or as a sense organ.
Test. The skeleton of an echinoid echinoderm. It consists of rows of fused plates.
Thorax. The division of an animal's body between the head and the abdomen.
Thread. A fine, slender, sculprural element that may be axial or spiral in gastropods; bivalves, radial or concentric.
Trochophore. The ciliated swimming larva of certain annelids, echiurans, sipunculans and mollusks.
Truncate. Having the end cut off squarely.
Tube foot. One of the numerous small appendages of an echinoderm, hydraulically operated and used in feeding or locomotion. Also, used as a sense organ, often tipped with a suction disk.
Tubercle. A large rounded bulge, bump, node or rounded projection on the surface of an animal.
Tunic. The covering of a tunicate's body; in compound tunicates, a thick mass in which many individuals are imbedded.
Turbinate. Top shaped.
Turreted. The tops of the whorls flattened.
Umbilicus. In gastropods, the opening at the base of a hollow columella, surrounded by the base of the body whorl. It is visible from below. It may be closed by an overgrowth of shell material (umbilical callus).
Umbo/umbones. In bivalves, the earliest part of the shell.
Umbonal ridge. In bivalves, an angled or rounded ridge beginning at the umbo and usually extending to the hind end of a valve.
Univalve. A shell composed of a single piece, as a snail.
Valve. One piece of a bivalve shell's two parts or one of the 8 plates that compose the dorsal shield of a chiton.
Varix/Varices. Thickening at former lip edge of a gastropod shell. prominent raised ribs on the surface of a snail shell, caused by periodic thickening of the outer lip during rest periods in the shell growth.
Varicose. Bearing one varix or more.
Veliger. A molluscan larva with a winglike swimming appendage on each side of its mouth.
Ventral. Of or relating to the underside
Ventricose. Swollen or rounded out.
Verticle. Going in the direction of the apex in the base of gastropod shells; in the direction of front to rear of chiton shells.
Visceral mass. That part of the molluscan body containing the visceral organs.
Viviparous. Live bearing, a term applied to animals whose eggs develop inside the body of the female a0nd in which larvae are born in an advanced stage.
Volutions. The distinct turns of the spire, also called whorls.
Water Vascular System. The system of canals in an echinoderm that hydraulically operates the tube feet.
Wing. In some bivalves, a flattened projection located at one or both ends of the hinge line. It is more or less a triangular projection or expansion of the shell of a bivalve, either in the plane or the hinge or extending above it as an ear.
Whorl. In spiral gastropods, one of the full turns of the shell.
Zoochlorella/Zoochlorellae. A green, photosynthesizing one celled plant that lives symbiotically inside cells or tissues of some invertebrates.
Zooid. An animal whose body is structurally continuous with that of others in a colonial species: examples, bryozoans, compound tunicates and hydroids.
Zoozanthella/Zooxanthellae. A yellow, photosynthesizing, one celled plant living symbiotically inside cells or tissues of some invertebrates.