_The Discerning of the Eastern Cretaceous._—The Cretaceous sequence was first determined by that “active and acute geologist,” Samuel G. Morton (1799–1851), but that these rocks might be present along the Atlantic border had been surmised as early as 1824 by Edward Hitchcock (=7=, 216). Vanuxem, as above pointed out, indicated the presence of the Cretaceous in 1829. In this same year Morton proved its presence before the Philadelphia Academy of Natural Sciences. Between 1830 and 1835 Morton published a series of papers in the Journal under the title “Synopsis of the Organic Remains of the Ferruginous Sand Formation of the United States, with Geological Remarks” (=17=, 274, _et seq._). In these he describes the Cretaceous fossils and demonstrates that the “Diluvial” and Tertiary strata of the Atlantic border also have a long sequence of Cretaceous formations. In the opening paper he writes: “I consider the marl of New Jersey as referable to the great ferruginous sand series, which in Prof. Buckland’s arrangement is designated by the name of green sand.... On the continent this series is called the ancient chalk ... lower chalk,” etc. Again, the marls of New Jersey are “geologically equivalent to those beds which in Europe are interposed between the white chalk and the Oölites.” This correlation is with the European Lower Cretaceous, but we now know the marls to be of Upper Cretaceous age. Although Eaton objected strenuously to Morton’s correlation, we find M. Dufresnoy of France saying, “Your limestone above green sand reminds me very much of the Mæstricht beds,” a correlation which stands to this day (=22=, 94, 1832). In 1833 Morton announces that the Cretaceous is known all along the Atlantic and Gulf border, and in the Mississippi valley. “The same species of fossils are found throughout,” and none of them are known in the Tertiary. He now arranges the strata of the former “Alluvial” as follows: Modern │Alluvial. „ │Diluvial. ─────────┼───────────────────────────────────────────────────────────── Tertiary │Upper Tertiary (Upper Marine). „ │Middle Tertiary (London Clay). „ │Lower Tertiary (Plastic Clay). ─────────┼─────────────────┬─────────────────────────────────────────── Secondary│Calcareous Strata│Cretaceous group, or Ferruginous Sand │ │ series (=24=, 128). „ │Ferruginous Sand │ „ _Western Cretaceous._—In 1841 and 1843 J. N. Nicollet announced the discovery of Cretaceous in the Rocky Mountain area. Of 20 species of fossils collected by him, 4 were said to occur on the Atlantic border, and of the 200 forms of the Atlantic slope only 1 was found in Europe. Here we see pointed out a specific dissimilarity between the continents, and a similarity between the American areas of Cretaceous deposits (=41=, 181; =45=, 153).