NATURAL HISTORY OF CREATION. loi 



an estuary again. 811011 changes the Paris l)asin 

 appears to have undergone oftener than once, for, lh>t. 

 we have there a fresh-water formation of cLay and lime- 

 stone beds; then, a marine limestone formation; next. 

 a second fresh-water formation, in which the material of 

 the celebrated i)lasteT of Paris (gypsum) is included ; 

 then, a second marine formation of sandy and limy 

 beds; and finally, a third series of fresh-water strata. 

 Such alternations occur in other examples of the tertiary 

 formation likewise. 



The tertiary beds present all but an entirely new set 

 of animals, and as we ascend in the series, we find more 

 and more of these identical with species still existing 

 upon earth, as if we had now reached the dawn of the 

 present state of the zoology of our planet. By tlio 

 study of the shells alone, Mr. Lyell has been enabled to 

 divide the whole term into four sub-periods, to which he 

 has given names with reference to the proportions which 

 they respectively present of surviving species — first, the 

 eocene (from rjws, the dawn ; ;(oii/oy, recent) ; second, tlie 

 miocene (fieioiv, less) ; third, older pliocene (nXecoiv, more) ; 

 fourth, newer pliocene. 



EOCENE SUB- PERIOD. 



The eocene period presents, in three continental groups, 

 1238 species of shells, of which forty-two, or 3*5 per 

 cent., yet flourish. Some of these are remarkable 

 enough ; but they all sink into insignificance beside the 

 mammalian remains which the lower eocene deposits of 

 the Paris basin present to us, showing that the lanc^ 

 had now become the theatre of an extensive creation of 

 the highest class of animals. Cuvier ascertained about 

 fifty species of these, all of them long since extinct. A 



