426 



SIR CHARLES LYELL 



character of their fossil from the % Eocene type, and approach 

 more and more to that of the living creation. In the present 

 state of science, it is chiefly by the aid of shells that we are 

 enabled to arrive at these results, for of all classes the tes- 

 tacea are the most generally diffused in a fossil state, and 

 may be called the medals principally employed by nature in 

 recording the chronology of past events. In the Upper 

 Miocene rocks (No. 5 of the table, p. 135) we begin to find 

 a considerable number, although still a minority, of recent 

 species, intermixed with some fossils common to the preced- 

 ing, or Eocene, epoch. We then arrive at the Pliocene strata, 

 in which species now contemporary with man begin to pre- 

 ponderate, and in the newest of which nine-tenths of the 

 fossils agree with species still inhabiting the neighbouring 

 sea. It is in the Post-Tertiary strata, where all the shells 

 agree with species now living, that we have discovered the 

 first or earliest known remains of man associated with the 

 bones of quadrupeds, some of which are of extinct species. 

 In thus passing from the older to the newer members of 

 the Tertiary system, we meet with many chasms, but none 

 which separate entirely, by a broad line of demarcation, one 

 state of the organic world from another. There are no 

 signs of an abrupt termination of one fauna and flora, and 

 the starting into life of new and wholly distinct forms. 

 Although we are far from being able to demonstrate geologi- 

 cally an insensible transition from the Eocene to the Miocene, 

 or even from the latter to the recent fauna, yet the more we 

 enlarge and perfect our general survey, the more nearly do 

 we approximate to such a continuous series, and the more 

 gradually are we conducted from times when many of the 

 genera and nearly all the species were extinct, to those in 

 which scarcely a single species flourished which we do not 

 know to exist at present. Dr. A. Philippi, indeed, after an 

 elaborate comparison of the fossil tertiary shells of Sicily 

 with those now living in the Mediterranean, announced, as 

 the result of his examination, that there are strata in that 

 island which attest a very gradual passage from a period 

 when only thirteen in a hundred of the shells were like the 

 species now living in the sea, to an era when the recent 

 species had attained a proportion of ninety-five in a hundred. 



