"North Wales itself — at all events the whole of the great Bala district where Sedgwick first worked out the physical succession among the rocks of the intermediate or so-called Upper Cambrian or Lower Silurian system; and in all probability much of the Shelve and the Caradoc area, whence Murchison first published its distinctive fossils — lay within the territory of the Ordovices ... Here, then, have we the hint for the appropriate title for the central system of the Lower Palaeozoics. It should be called the Ordovician System, after this old British tribe" (pp. 13-14): Charles Lapworth, "On the Tripartite Classification of the Lower Palaeozoic Rocks" in Geological Magazine decas 2 vol. 6 (1879) pp. 1-15
De historia nominis definitionisque vide: Mary Grace Wilmarth, The Geologic Time Classification of the United States Geological Survey Compared With Other Classifications, accompanied by the original definitions of era, period and epoch terms (United States Geological Survey Bulletin no. 769. Vasingtoniae: U.S. Government Printing Office, 1925) (p. 83 apud Google Books)
