Texas Fossils: a Project Gutenberg eBook

Suture—the line of junction between two parts; in crinoids, the line of junction between two plates; in gastropods, the line of junction of the whorls as seen on the exterior of the shell; in cephalopods, the line of junction between a septum and the shell wall.

Symmetry—orderly arrangement of parts of an object with reference to lines, planes, or points.

Bilateral symmetry—the symmetrical duplication of parts on each side of a vertical anterior-posterior plane.

Radial symmetry—the symmetrical repetition of parts around a common vertical dorso-ventrally disposed axis.

System—the rocks formed during a period; the time-stratigraphic term next in rank above a series.

Taxonomy—that branch of science that deals with classification, especially in relation to plants, animals, or fossils.

Theca—a sheath or case; in coelenterates, the bounding wall at or near the margin of the exoskeleton; in echinoderms, the main body skeleton (or calyx) which houses the animal’s soft parts; in graptolites, any cup or tube of the colony.

Thorax—in trilobites, that part of the body between the cephalon and pygidium.

Time-unit—a portion of continuous geologic time (e.g., eras, periods, epochs, and ages).

Time-stratigraphic unit—term given to rock units with boundaries established by geologic time; strata deposited during definite portions of geologic time (e.g., systems, series, stages, etc.).

Topographic map—a map showing the physical features of an area, especially the relief and contour of the land.

Trilobite—an extinct marine arthropod having a flattened segmented body covered by a hardened dorsal exoskeleton divided into three lobes.

Trivial name—the Latinized name added to a generic name to distinguish the species; same as specific name.

Type locality—the geographic location at which a formation was first described and from which it was named; or from which the type specimen of a fossil species comes.

Type specimen—the individual or specimen on which the original designation of a species was established.

Umbilicus—an external depression or opening at the center of many loosely coiled shells; in gastropods it is usually located at the base of the shell; in cephalopods it is usually located laterally.

Variety—a subdivision of a species, designated by a third name when a variety is designated.

Ventral—pertaining to the abdomen; as opposed to dorsal, pertaining to the back.

Zooecium (plural, zooecia)—tube or chamber occupied by an individual of the bryozoan colony; also called an autopore.

Footnotes

[1]Associate Professor of Geology, Lamar State College of Technology, Beaumont, Texas.

[2]Entries marked with asterisk are published by the Bureau of Economic Geology, The University of Texas, Austin. Those not out of print are distributed at nominal sale price; list sent on request. These publications may be consulted at many public libraries and/or Chamber of Commerce offices.

Footnotes

Index