1887.] Professor Sacco on Origin of Great Alpine Lakes. 275 
Italy they can only be of Astian or Quaternary age. Indeed, it 
seems to me probable that just as in Switzerland, those unfossili- 
ferous accumulations may truly belong in part to each of the stages 
referred to — namely, to the Messinian, the Piacentian, the Astian, 
and the Quaternary — so the unfossiliferous conglomerates in the 
valley of the Po may belong in part to the Upper Pliocene, and in 
part also to the Quaternary. I shall not attempt at present, how- 
ever, to make this distinction, because it is still matter of doubt, 
and would lead me into too long a discussion of what, after all, are 
local details. Nevertheless, I should like to point out some of the 
more important results obtained from a geological examination of 
the upper valley of the Po. These may be summarised as follows : — 
1. In certain parts of Piedmont, at a distance of more than 50 
kilometres from the Maritime Alps, with their important valleys and 
rivers (as, for example, between Villanuova and Villafranca, Asti), 
there occur fluviatile and lacustrine deposits, consisting of marls, 
sand, gravel, and conglomerate, which sometimes attain a thickness 
of 100 metres, and which from their fossils, studied by me for some 
years, I judge to be of Pliocene age (Villafranchian of Pareto). 
These alluvial deposits rest upon the yellow sands of the Astian, 
which in that district are of inconsiderable thickness. 
2. In the valley of the Stura (Cuneo),* and in certain other dis- 
tricts of Piedmont, one may see the yellow marine sands of Astian 
age thinning off towards the mountains, taking on by degrees the 
character of true littoral deposits, and then of marshy or lagoon-like 
accumulations. Followed nearer the mountains, these accumula- 
tions are covered and replaced by gravelly, sandy, and argillaceous 
alluvia, which at first are probably marine, but seem to pass later- 
ally into true continental deposits. The numerous fossils found by 
me in these beds prove the latter to be of Upper Pliocene age. 
3. In other regions of Piedmont, but nearer the mountains, as, 
for example, between Morozzo and Yillanuora, Mondovi, the alluvia 
in question repose conformably upon the marine blue marls of the 
Piacentian, presenting in this manner a well-marked parallelism 
with the yellow marly sands, which at a distance of only two kilo- 
metres represent the marine Astian, and overlie the same horizon of 
* F. Sacco, “La valle della Stura di Cuneo dal ponte del! Olla/' &c., 
Atti Soc. It. Sc. Nat., xxix. 1886. 
