550 HISTORICAL PALAEONTOLOGY. 



Claiborne, Alabama, and consist of clays, lignites, marls, and 

 impure limestones. The fossils of the Claiborne series are 

 much the same in their characters as those of the London 

 clay, and the lignites contain numerous plant-remains. 



The Middle Eocene group is represented in North America 

 by lignitic clays and marls which occur at Jackson, Mississippi. 

 Amongst the more remarkable fossils of the Jackson beds are 

 the teeth and bones of Cetaceans of the genus Zeuglodon. 



Rocks of Upper Eocene age occur in North America at 

 Vicksburg, Mississippi, and consist of lignites, clays, marls, 

 and limestones. On the White River they are about 1000 

 feet thick, and consist of clays, sandstones, and limestones, of 

 fresh-water origin. Among their most remarkable fossils are 

 the remains of Mammals, of which about forty species have 

 been already determined. 



LIFE OF THE EOCENE PERIOD. 



Little need be added here as to the life of the Eocene 

 period, fossils being so abundant as to render it impossible to 

 do more than indicate some general considerations. Upon 

 the whole, the plants and animals of the Eocene period closely 

 resemble those now in existence upon the globe ; not, how- 

 ever, necessarily in the exact localities in which they are now 

 found. Thus, the modern representatives of the plants and 

 animals of the Eocene Rocks of Europe are not to be found 

 in Europe itself, but in some tropical or sub-tropical region. 

 The climatic conditions of Europe in the Eocene period were 

 very different to those at present subsisting, and the animals 

 and plants were correspondingly different. Still, there are 

 few Eocene fossils which have not their modern representa- 

 tives in warm countries. 



The Protozoa are represented in Eocene times chiefly by 

 ForaminiferO) which are often extraordinarily abundant, and 

 the shells of which may in some cases be said without exagge- 

 ration to compose whole mountain-masses. The great and 

 widespread formation of the Nummulitic Limestone is largely 

 made up of the shells of Nummulites and Orbitoides, some of 

 the former occasionally reaching a size of more than an inch 

 in diameter. One of the limestones of the Paris basin is 

 largely composed of the shells of a species of Miliola. Nume- 

 rous other forms occur ; and the genus Nummulites is exclu- 

 sively confined to this formation. 



Corals are not particularly abundant in the Eocene rocks, 

 but they are mostly of types identical with, or nearly allied to, 



