Selected papers from the August 1988 symposium on the Ordovician System. Authors from the U.K., Canada, Australia, and the U.S. contributed papers on a project to redefine regional chronostratigraphic subdivisions. Papers also cover Ordovician paleontology and biostratigraphy, emphasizing conodonts, graptolites and trilobites. The interrelationships of stratigraphy, eustasy, tectonics, and volcanisms are explored, with particular attention to the Appalachian Orogen. The final section of the volume documents some of the new data and interpretations of Ordovician paleo-oceanography, paleoclimatology, and paleogeography.