CHAP, ii.] THE EOCENE CLASSIFICATION. 15 



other forms intermediate between the marsupials and 

 the true placental mammals. 



The Eocene strata 1 are found in the area to the 

 south-east of a line passing from the Wash to Charmouth 

 in Dorsetshire, and are mainly centered in two basins, 

 named, respectively, that of London, and that of Hamp- 

 shire and the Isle of Wight. They occur over a very 

 wide area on the continent. They are 

 divided into three groups, the lower 

 or Pre-nummulitic, the middle or the 

 Nummulitic, and the upper or the 

 Post-nummulitic, the widely spread 

 foraminifer, Nummulites (Fig. 2), offer- 

 ing a ready means of determination of Nummulites isevigata. 

 age, not merely in Europe, but through- Brackiesham, f 

 out Asia, and a large part of Africa. The following 

 table represents the thickness, characters, and condi- 

 tions of deposit of each of the subdivisions in England, 

 together with their equivalents in France, as determined 

 by the recent researches of Professor Gaudry. 



1 For a systematic account of the Eocene strata, see Lyell, Student's 

 Elements, c. xvi. 



