In North America the Eocene formations occupy a large area bordering the Atlantic, which increases in breadth and importance as it is traced southwards from Delaware and Maryland to Georgia and Alabama. They also occur in Louisiana and other states both east and west of the valley of the Mississippi. At Claiborne in Alabama no less than four hundred species of marine shells, with many echinoderms and teeth of fish, characterize one member of this system. Among the shells the Cardita planicosta, before mentioned ([fig. 171.] [p. 199.]), is in abundance; and this fossil, and some others identical with European species, or very nearly allied to them, make it highly probable that the Claiborne beds agree in age with the central or Bracklesham group of England, and the calcaire grossier of Paris.[206-B]
Higher in the series is a remarkable calcareous rock, formerly called "the nummulite limestone," from the great number of discoid bodies resembling nummulites which it contains, fossils now referred by A. d'Orbigny to the genus Orbitoides, which has been demonstrated by Dr. Carpenter to belong to the Foraminifera.[206-C] The following section will enable the reader to understand the position of the three subdivisions of the series, Nos. 1, 2, and 3., the relations of which I ascertained in Clarke County, between the rivers Alabama and Tombeckbee.
Fig. 190.
| 1. Sand, marl, &c., with numerous fossils. | } | Eocene. | ||
| 2. White or rotten limestone, with Zeuglodon. | ||||
| 3. Orbitoidal, or so called nummulitic limestone. | ||||
| 4. Overlying formation of sand and clay without fossils. | Age unknown. |
The lowest set of strata, No. 1., having a thickness of more than 100 feet, comprise marly beds, in which the Ostrea sellæformis occurs, a shell ranging from Alabama to Virginia, and being a representative form of the Ostrea flabellula of the Eocene group of Europe. In others beds of No. 1., two European shells, Cardita planicosta, before mentioned, and Solarium canaliculatum are found, with a great many other species peculiar to America. Numerous corals, also, and the remains of placoid fish and of rays occur, and the "swords," as they are called, of sword fishes, all bearing a great generic likeness to those of the Eocene strata of England and France.
No. 2. ([fig. 190.]) is a white limestone, sometimes soft and argillaceous, but in parts very compact and calcareous. It contains several peculiar corals, and a large Nautilus allied to N. zigzag, also in its upper bed a gigantic cetacean, called Zeuglodon by Owen.[207-A]
