Champlain (1842) or Ordovician (1879) period. Arenig to top of Caradoc in Europe. Beekmantown to top of Richmondian in America. Cambrian period. In the Atlantic realm, begins with the Paradoxides, and in the Pacific, with the Bathyuriscus and Ogygopsis faunas. The close is involved in Ulrich’s provisionally defined Ozarkian system. When the latter is established, the Ozarkian period will hold the time between the Ordovician and the Cambrian. Taconic period. For the world-wide Olenellus or Mesonacidæ faunas. _Paleogeography._ When geologists began to perceive the vast significance of Hutton’s doctrine that “the ruins of an earlier world lie beneath the secondary strata,” and that great masses of bedded rocks are separated from one another by periods of mountain making and by erosion intervals, it was natural for them to look for the lands that had furnished the debris of the accumulated sediments. In this way paleogeography had its origin, but it was at first of a descriptive and not of a cartographic nature. The word paleogeography was proposed by T. Sterry Hunt in 1872 in a paper entitled “The Paleogeography of the North American Continent,” and published in the Journal of the American Geographical Society for that year. It has to do, he says, with the “geographical history of these ancient geological periods.” It was again prominently used by Robert Etheridge in his presidential address before the Geological Society of London in 1881. Since Canu’s use of the term in 1896, it has been frequently seen in print, and now is generally adopted to signify the geography of geologic time. The French were the first to make paleogeographic maps, and Jules Marcou relates in 1866 that Elie de Beaumont, as early as March, 1831, in his course in the College of France and at the Paris School of Mines, used to outline the relation of the lands and the seas in the center of Europe at the different great geologic periods. His first printed paleogeographic map appeared in 1833, and was of early Tertiary time. Other maps by Beaumont were published by Beudant in 1841–1842. The Sicilian geologist Gemmellaro published six maps of his country in 1834, and the Englishman De La Beche had one in the same year. In America the first to show such maps was Arnold Guyot in his Lowell lectures of 1848. James D. Dana published three in the 1863 edition of his Manual of Geology. Of world paleogeographic maps, Jules Marcou produced the first of Jurassic time, publishing it in France in 1866, but the most celebrated of these early attempts was the one by Neumayr published in 1883 in connection with his Ueber klimatische Zonen während der Jura- und Kreidezeit.