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Show xii PREFACE• found that Signor 0. G. Costa had examined the tertiary fossils which I had sent to him from different parts of Sicily, and declared them to be for the most part of recent species. I then bent my course homeward, seeing at Genoa, Professor Viviani and Dr. Sasso, the last of whom put into my hands his memoirs on the strata of Albenga (see vol. iii. p. 166), in which I found, that, according to his list of shells, the tertiary formations at the foot of the maritime Alps contained about 50 per cent. of recent species. I next re-visited Turin, and communicated to Signor Bonelli the result of my inquiries respecting the tertiary beds of the south of Italy, and of Sicily, upon which he kindly offered to review his fossils, some of which had been obtained from those countries, and to compare them with the Subapennine shells of northern Italy. He also promised to draw up immediately a list of the shells characteristic of the greensand of the Superga, and common to that locality and Bordeaux, that I might publish it at the end of my second volume; but the death of this amiable and zealous naturalist soon afterwards deprived me of the benefit of his assistance. I had now fully decided on attempting to establish four sub-divisions of the great tertiary epoch, the same which are fully illustrated in the present work. I considered the basin of Paris and London to be the type of the first division; the beds of the Superga, of the second; the Subapennine strata of northern Italy) PREFACE. xiii of the third ; and Ischia and the Val di N oto, of the fourth. I was also convinced that I had seen proofs, during my tour in Auvergne, Tuscany and Sicily, of volcanic rocks contemporaneous with the sedimentary strata of three of the above periods. i On my return to Paris, in February, 1829, I communicated to M. Desnoyers some of the new views to which my examination of Sicily had led me, and my intention to attempt a classification of the different tertiary formations in chronological order, by reference to the comparative proportion of living species of shells found fossil in each. He informed me, that during my tour he had been employed in printing the first part of his memoir, not yet published, 'on the Tertiary Formations more recent than the Paris basin,' in which he had insisted on the doctrine 'of the succession of tertiary formations of different ages.' At the ~nd of the first part of his memoir, which was published before I left Paris*, he annexed a note on the accordance of many of my views with his own, and my intention of arranging the tertiary formations chronologically, according to the relative number of fossils in each group, which were identifiable with species now living. At the same time I learned from M. Desnoyers, that M. Deshayes had, by the mere inspection of the fossil shells in his extensive museum, convinced him~ elf that the different tertiary formations might be • Ann, des Sci. Nat., tome xvi. p. 214. |