XIV PREFACE. 



arranged in a chronological series. I accordingly lost 

 no time in seeing M. Deshayes, who explained to me 

 the data on which he considered that the three ter- 

 tiary periods mentioned in the Tables, Appendix I., 

 might be established. I at once perceived that the 

 fossils obtained by me in my tour would form but an 

 inconsiderable contribution to so great a body of 

 zoological evidence as M. Deshayes had already in 

 his possession. I therefore requested him to examine 

 my shells when they arrived from Italy, and expressed 

 my great desire to obtain his co-operation in my work, 

 in which, as will appear in the sequel, I was fortunate 

 enough to succeed. 



| T}ie preparation of my first volume had now been 

 | suspended for nine months, and was not resumed until 

 my return to London in the beginning of March, 

 1829. Before the whole was printed another summer 

 arrived, and I again took the field to examine 'the 

 Crag,' on the coasts of Essex, Norfolk, and Suffolk. 

 The first volume appeared at length in January, 1830, 

 after which I applied myself to perfect what I had 

 written on 'the changes in the organic world,' a 

 subject which merely occupied four or five chapters 

 in my original sketch, but which was now expanded 

 into a small treatise. Before this part was completed 

 another summer overtook me, and 'I then set out on 

 a geological expedition to the south of France, the 

 Pyrenees, and Catalonia. 



On my return to Paris, in September, 1830, I 



