Ch. XVI.] eocene strata in the united states. 309 



mulites and their accompanying testacea were nn question ably inhabit- 

 ants of salt water. Before these events, comprising the conversion 

 of a wide area from a sea to a continent, England had been peopled, 

 as I before pointed out (p. 294), by various quadrupeds, by herbiv- 

 orous pachyderms, by insectivorous bats, and by opossums. 



Almost all the extinct volcanoes which preserve any remains of 

 their orio-inal form, or from the craters of which lava streams can be 

 traced, are more modern than the Eocene fauna now under consider- 

 ation ; and besides these superficial monuments of the action of heat, 

 Plutonic influences have worked vast changes in the texture of rocks 

 within the same period. Some members of the nummulitic and 

 overlying tertiary strata called fiysch have actually been converted in 

 the central Alps into crystalline rocks, and transformed into marble, 

 quartz-rock, mica-schist, and gneiss.* 



EOCENE STRATA IN THE UNITED STATES. 



In North America the Eocene formations occupy a large area bor- 

 dering the Atlantic, which increases in breadth and importance as it 

 is traced southward 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 echino- 

 derms and teeth of fish, characterize one member of this system. 

 Among the shells, the Cardita planicosta, before mentioned (fig. 235, 

 p. 288), 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 with the calcaire grossier of 

 Paris, f 



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 demon- 

 strated by Dr. Carpenter to belong to the foraminifera.f That natu- 

 ralist, moreover, is of opinion that the Orbitoides alluded to (0. 

 Mantelli) is of the same species as one found in Cutch in the Middle 

 Eocene or nummulitic formation of India. The following section 

 will enable the reader to understand the position of three subdivis- 

 ions of the Eocene series, Nos. 1, 2, and 3, the relations of which I 



. * Murchison, Quart. Journ. of Geol. Soc, vol. v., and Lyell, vol. vi., 1850. An- 

 niversary Address. 



\ See paper by the Author, Quart. Journ. Geol. Soc, vol. iv. p. 12 ; and Second 

 Visit to the U. S., vol. ii. p. 59. 



X Quart. Journ. Geol. Soc., vol. vi. p. 32. 



