Here are some USGS Web pages with more information on trilobites and Anywhere:
Early Paleozoic biochronology of the Great Basin, western United States
Publication (PDF format)in three parts on the biostratigraphy and lithostratigraphy of the Ibexian Series in the North American Ordovician, with sections on the southern Egan Range, Nevada and the biostratigraphy of the eastern Great Basin.
(Score: 0.509)
Definition:
Any of numerous extinct marine arthropods of the class Trilobita, of the Paleozoic Era, having a segmented body divided by grooves into three vertical lobes and found as fossils throughout the world. [American Heritage Dic. of the English Language, 4th ed.]