PREFACE. 
found that Signor O. G. Costa had examined the ter- 
tiary 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 home- 
ward, seeing at Genoa, Professor Vivian i 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 ter- 
tiary 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 imme- 
diately a list of the shells characteristic of the green- 
sand 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, 
