_North America._—The Eocene witnessed quite extensive geographical changes, though but little is known of it in Central or South America, or the West Indies. Along the Atlantic and Gulf coasts of the United States there was an extensive submergence of the coastal plain, the sea covering the southern half of New Jersey and extending thence to the southwestward in an ever broadening band, through the South Atlantic and Gulf states. Northern Florida was under water and the Gulf extended as a narrow sound, known as the “Mississippi Embayment,” up the valley of that river to southern Illinois and westward into Texas. The Embayment was present in the Cretaceous and again in the Eocene, but it is not known whether it persisted through the Paleocene; probably it did not, as the whole Atlantic coast region appears to have stood at a higher level then than now. While the condition of Mexico and Central America during the Eocene is not known in any save the vaguest manner, it is evident that there was then a broad communication between the Atlantic and the Pacific, completely severing North and South America, though the place of this transverse sea has not been fixed. On the Pacific side, a long, narrow arm of the sea occupied what is now the great valley of California, extending north into Oregon and Washington. It will be noted that in North America the Eocene sea was almost confined to the neighbourhood of the present coast-lines, nowhere penetrating very far inland, except in the Mississippi Embayment, and thus differing widely from the condition of Europe at that epoch, where much of what is now land was submerged. The greatly expanded Mediterranean covered most of southern Europe, where the great mountain ranges, the Pyrenees, Alps, etc., had not yet been formed. Very important, from the point of view of American geography, is the fact that Europe was completely separated from Asia by a narrow strait or sea, which ran down the eastern side of the Ural Mountains from the Arctic Ocean and joined the enlarged Mediterranean. During the existence of this Ural Sea any land connection of North America with Europe must necessarily have been by means of a North Atlantic bridge, or by one across the Arctic Sea, since communication with Asia by way of Alaska would not have reached eastern Europe. [Illustration: FIG. 48.—Map of North America during the Eocene epoch. The present limits of the continent are shown in outline; white areas = land; horizontal lines = sea; dotted areas = non-marine deposits; black circles with white dots = active volcanoes. (After Schuchert.)]