Amber—a hard, yellowish, translucent, fossilized plant resin.
Ammonite—ammonoidcephalopodwith complexly wrinkledsuturepattern; member of subclass Ammonoidea.
Anterior—front or fore.
Anus—the terminal opening of the alimentary canal, through which waste matter is discarded from the body.
Aperture—the opening of shells, cells, etc.
Aragonite—calcium carbonate (CaCO₃) crystallizing in a different form thancalcite. In shells it is chalky and opaque; is less stable than calcite.
Archeozoic—the oldest known geological era; earlyPrecambriantime.
Articulated—joined by interlocking processes or by teeth and sockets.
Asymmetrical—without or lackingsymmetry.
Bilateral—pertaining to the two halves of a body as symmetrical and mirror images of each other.
Binomial nomenclature—systemof scientific nomenclature requiring two names: generic and trivial.
Blastoid—stalkedechinodermwith bud-likecalyxusually consisting of 13 plates; member of class Blastoidea.
Brachiopod—bivalved marine invertebrate; member ofphylumBrachiopoda.
Brackish—a mixture of salt and fresh waters.
Burrow—a hole in the ground,rock, wood, etc., made by certain animals for shelter or while gathering food.
Calcareous—composed of, or containing, calcium carbonate; limy.
Calcite—calcium carbonate (CaCO₃) crystallizing in a different form thanaragonite. In shells it is translucent and more stable than aragonite.
Cambrian—the first (oldest)periodof thePaleozoicera.
Calyx—in corals the bowl-shaped depression in the upper part of the skeleton; in stalked echinoderms that part of the body which contains most of the soft parts.
Caprinid—aCretaceouspelecypodthat is typically coiled in the form of a ram’s horn.
Carapace—the hard protective covering that forms theexoskeletonof many invertebrates; in arthropods it is usuallychitinousor calcaro-chitinous.
Carbonization—the process of fossilization whereby organic remains are reduced to carbon or coal.
Cast—the impression taken from a mold.
Cenozoic—the latest era of geologic time, following theMesozoicera and extending to the present.
Cephalon—the head; in trilobites theanteriorbodysegmentforming the head.
Cephalopod—marine invertebrate with well-defined head and eyes and with tentacles around the mouth; member of class Cephalopoda,phylumMollusca; includes squids, octopuses, pearly nautilus.
Ceratite—an ammonoidcephalopodwithsuturecomposed of rounded saddles and jagged lobes; member of subclass Ammonoidea.
Chert—a cryptocrystallinevarietyofsilica; flint is a variety ofchert.
Chitin—a horn-like substance, found in the hard parts of many animals, such as beetles, crabs, etc.
Chitinous—composed ofchitin.
Cirri—in crinoids, the jointed appendages which branch off the side of the stem or from the base of some crinoid stems.
Coelenterate—invertebrates characterized by a hollow body cavity, radialsymmetry, and stinging cells; a member ofphylumCoelenterata; includes jellyfishes, corals, sea anemones.
Colonial—in biology refers to the way in which some invertebrates live in close association with, and are more or less interdependent upon, each other;colonialcorals, hydroids, etc.
Columella—a small column or central axis; in corals the small rod or axial pillar in the center of thecorallite; in gastropods the solid or perforate pillar formed by the union of the successive coils of a conispiral shell.
Columnal—one of the disk-shaped segments of a crinoid stalk.
Concentric—having a common center, as circles; refers to shell markings that are parallel to shell margin.
Concretion—nodular or irregular masses in sedimentary rocks and usually formed around a central core, which is often afossil.
Conical—cone-shaped.
Conodont—minute tooth-like fossils found in certainPaleozoicrocks; their origin is not definitely known, but they may have been part of some type of extinct fish.
Coral—bottom-dwelling marine invertebrate that secretescalcareoushard parts; member of class Anthozoa,phylumCoelenterata.
Corallite—the skeleton formed by an individualcoralanimal; may besolitaryor form part of a colony.
Corallum—the skeleton of acoralcolony.
Corona—crown; in echinoids the main part of the skeleton consisting of symmetrically arrangedcalcareousplates.
Coprolite—thefossilexcrement of animals.
Correlation—the process of demonstrating that certain strata are closely related to each other or that they are stratigraphic equivalents.
Cretaceous—the third and lastperiodof theMesozoicera.
Cystoid—an extinct stemmedechinodermwithcalyxcomposed of numerous irregularly arranged plates; member of class Cystoidea.
Dendritic—resembling a tree, branching.
Dentition—thesystemor arrangement of teeth peculiar to any given animal.
Devonian—the fourth oldestperiodof thePaleozoicera, follows theSilurian, precedes theMississippian.
Dip—the angle of inclination which the bedding plane of rocks makes with a real or imaginary horizontal line.
Distillation—in fossils that process by which volatile organic matter is removed, leaving a carbon residue.
Dolomite—a mineral composed of calcium magnesium carbonate (CaMg(CO₃)₂).
Dorsal—pertaining to the back.
Echinoderm—a marine invertebrate withcalcareousexoskeletonand usually exhibiting a five-foldradial symmetry; member ofphylumEchinodermata; includes cystoids, blastoids, crinoids, starfishes, and sea urchins.
Echinoid—bottom-dwelling, unattached marine invertebrate withexoskeletonofcalcareousplates covered by movable spines; member of class Echinoidea; sea urchins, heart urchins, biscuit urchins.
Endoskeleton—the internal supporting structure of an animal.
Eocene—the next to earliest of theTertiaryepochs, follows thePaleoceneand precedes theOligocene.
Equivalved—right and left valves subequal and (except for hinge structures) comprising mirror images of each other.
Evolution—a term applied to those methods or processes and to the sum of those processes whereby organisms change through successive generations.
Exoskeleton—an external skeleton, or hard covering for the protection of soft parts, particularly among invertebrates.
Fault—the displacement of rocks along a zone of fracture.
Fauna—an assemblage of animals (living orfossil) living in a given place at a given time.
Flank—the side orlateralportion of anything.
Flora—an assemblage of plants (living orfossil) living in a given place at a given time.
Fold—in brachiopods, a major rounded elevation of shell which affects both inner and outer shell surfaces.
Foramen—in brachiopods, the opening in the pediclevalvenear the beak where the pedicle extends through the shell.
Foraminifer—a protozoan usually possessing acalcareous, perforated, chambered shell, but shell may bechitinousor agglutinated; a member of the order Foraminifera,phylumProtozoa.
Formation—arock unituseful for mapping and distinguished primarily on the basis of lithologic characters.
Fossil—the remains or traces of organisms buried by natural causes and preserved in the earth’s crust.
Guide fossil—afossilwhich, because of its limited vertical but wide horizontal distribution, is of value as a guide or index to the age of the rocks in which it is found.
Fossiliferous—containing fossilized organic remains.
Fusulinid—a spindle-shapedforaminifer:testshaped like a grain of wheat.
Gastrolith—highly polished well-rounded pebbles found associated with certain reptilian fossils; “stomach stones.”
Gastropod—a terrestrial or aquatic invertebrate, typically possessing a single-valved,calcareous, coiled shell; member of class Gastropoda,phylumMollusca: snails and slugs.
Geologic age—the age of an object as stated in terms of geologic time (e.g., aPennsylvanianfern,Cretaceousdinosaur).
Geologic map—map showing distribution ofrockoutcrops, structural features, mineral deposits, etc.
Geologic range—the known duration of an organism’s existence throughout geologic time (e.g.,Cambrianto Recent for brachiopods).
Glauconite—a greenish mineral commonly formed in marine environments and essentially a hydrous silicate of iron and potassium.
Goniatite—an ammonoidcephalopodwithsuturecomposed of smooth saddles and simple angular lobes; member of subclass Ammonoidea.
Graptolite—an extinct, marine,colonialorganism withchitinoushard parts; believed to belong to subphylum Hemichordata ofphylumChordata.
Guide fossil—seeFossil.
Habitat—the physical environment in which an organism lives.
Hinge-line—in brachiopods, the edge of the shell where the two valves articulate; in pelecypods, thedorsalmargin of thevalvewhich is in continual contact with the opposite valve.
Igneous rock—rocks which have solidified from lava or moltenrockcalled magma.
Index fossil—seeFossil.
Inequivalved—opposite valves unlike in shape or size, or both.
Jurassic—second oldestperiodof theMesozoic; follows theTriassic, precedes theCretaceous.
Keel—a strong continuous ridge along theventralside of ammonites.
Larva—the young form of some animals before they assume the mature shape.
Lateral—side or to the side.
Lithology—the study and description of rocks based on the megascopic (with the naked eye) examination of samples. Used also to refer to the texture and composition of any givenrocksample.
Living chamber—in mollusks, that part of the shell which is occupied by the living animal.
Lobe—in cephalopods, the backward flexure of thesutureorseptum.
Longitudinal—in a direction parallel with the length.
Lophophore—in brachiopods, a tentacle-bearing appendage attached to theanteriorsurface of themantlecavity.
Mantle—in mollusks and brachiopods, a layer of tissue containing cells that secrete the shell.
Meso-—a prefix signifying middle.
Mesozoic—that era of geologic time that precedes theCenozoicand follows thePaleozoic.
Miocene—fourth oldest epoch of theTertiaryperiod; follows theOligocene, precedes thePliocene.
Mississippian—fifth oldestperiodof thePaleozoic: follows theDevonian, precedes thePennsylvanian.
Multicellular—composed of more than one cell.
Nacreous—pearly.
Node—a knob.
-oid—a suffix meaning “in the form of.”
Oligocene—the third oldest epoch of theTertiaryperiod: precedes theMiocene, follows theEocene.
Operculum—the lid or covering of theapertureof certain shells.
Oral—referring to the mouth oraperture.
Orbitoidids—foraminifers with large typically disk-shaped tests.
Ordovician—second oldestperiodof thePaleozoicera; follows theCambrian, precedes theSilurian.
Ossicle—loosely used as a small plate.
Paleocene—oldest epoch of theTertiaryperiod; precedes theEocene.
Paleozoic—that era of geologic time that followsPrecambriantime and precedes theMesozoicera.
Pedicle opening(pedicleforamen)—seeForamen.
Pelecypod—a bivalved aquatic invertebrate; member of class Pelecypoda,phylumMollusca.
Pennsylvanian—the sixth oldestperiodof thePaleozoicera; follows theMississippian, precedes thePermian.
Period—a division of geologic time (Pl. 1).
Periostracum—the horny outer covering or epidermis on shells.
Permian—seventh and lastperiodof thePaleozoic.
Permineralization—that process by which mineral matter has been added to the original shell material by precipitation in the interstices rather than replacing the original shell material.
Phosphatic—containing or pertaining to phosphate minerals.
Phylum—one of the primary divisions of the animal or vegetable kingdoms.
Planispiral—shell coiled in one plane.
Pleistocene—earliest epoch ofQuaternaryperiod,Cenozoicera; followsPlioceneepoch ofTertiaryperiod, precedes Recent epoch of Quaternary.
Pleural—referring to the side or ribs; in trilobites, refers tolateralportions ofthoraxand pygidium.
Pliocene—latest epoch ofTertiaryperiodofCenozoicera; followsMioceneepoch and precedesPleistoceneepoch ofQuaternaryperiod.
Polygonal—many sided or having many-sided plates.
Polyp—a many-tentacled aquaticcoelenterateanimal, typically cylindrical or cup-shaped, as in corals.
Porcelaneous—like porcelain.
Pore—a very small opening.
Posterior—situated behind; to the rear.
Precambrian—that portion of geologic time before theCambrian; divided intoArcheozoicera (EarlyPrecambrian) andProterozoicera (Late Precambrian).
Protero—combining form meaning fore, former, oranteriorin time (Greekproteros, fore).
Proterozoic—youngest era of thePrecambrian; follows theArcheozoicera and precedes theCambrianperiodof thePaleozoicera.
Protista—the organic kingdom including the simplest of all one-celled organisms which possess various characters of both plants and animals; bacteria, algae, foraminifers, radiolarians.
Protoconch—in mollusks, the initial chamber of shell.
Pyrite—a hard, brass-yellow mineral composed of iron sulfide; “fool’s gold.”
Quaternary—the youngestperiodof theCenozoicera, follows theTertiaryperiod.
Radial symmetry—seeSymmetry.
Reef—a mound-like or ridge-like elevation of the sea bottom which almost reaches the surface of the water, composed primarily of organic material and commonly formed by reef-building animals, such as corals and oysters.
Replacement—type of fossilization whereby hard parts of organisms are removed by solution accompanied by almost simultaneous deposition of other substances in the resulting voids; mineralization.
Respiration—the process of oxygenation.
Rock—an aggregation of one or more minerals.
Rock-unit—divisions of rocks based on definite physical and lithologic characteristics and not defined on the basis of geologic time alone; groups, formations, members.
Rudistid—aCretaceouspelecypodthat does not exhibit the typical clam or oyster shape; many are cone-shaped, resembling corals.
Saddle—in cephalopods, the forward flexure (curved toward theaperture) of thesutureorseptum.
Scaphopod—an exclusively marine mollusk with a single-valved tusk-shaped shell; member of class Scaphopoda,phylumMollusca.
Scavenger—an animal that feeds on organic refuse.
Sedentary—stationary in life, not moving from place to place.
Sediment—material that has been deposited by settling from a transportation agent such as water or air; typically composed of weatheredrockfragments.
Sedimentary rock—rocks formed from the accumulation and lithification of sediments.
Segment—one of the parts into which a body naturally separates or is divided; for example, segments of arthropods or annelid worms.
Septal—pertaining to theseptum.
Septum(plural,septa)—a dividing wall or partition; in fusulinids, a partition between chambers in thefusulinidshell; in corals, one of the radiating,longitudinal,calcareousplates located within thecorallite; in cephalopods, thetransversepartitions between the chambers.
Series—the rocks formed during an epoch; the time-stratigraphic term next in rank below asystem.
Serrate—notched like a saw.
Sessile—animal attached to the sea floor more or less permanently.
Silica—an oxide of silicon (SiO₂).
Siliceous—containing or pertaining tosilica.
Silicification—the process of combining or impregnating withsilica.
Silurian—the third oldestperiodof thePaleozoicera; follows theOrdovician, precedes theDevonian.
Sinus—an elongate depression onbrachiopodshells.
Siphuncle—in cephalopods, the segmented horny orcalcareoustube which extends from theprotoconchto the living chamber.
Slickensides—polished and grooved surfaces that are the result of tworockmasses sliding past each other as in faulting.
Solitary—living alone; not part of a colony.
Species—one of the smaller natural divisions in classification.
Specific name—seeTrivial name.
Spicule—a minute spike or dart, skeletal element in sponges and holothurians.
Stratum(plural,strata)—a single bed or layer ofrock.
Strike—the direction of a real or imaginary line that is formed by the intersection of a bed orstratumwith a horizontal plane;strikeis perpendicular to thedip.