64 
NEWER PLIOCENE PERIOD. 
[Ch. VI. 
from Catania to Syracuse, has an opportunity of observing, 
on the sides of the valley, many deep sections of the modern 
formations above described, especially if he makes a slight 
detour by Sortino and the Valley of Pentalica. 
The whole series of strata, in the Val di Noto, is divisible 
into three principal groups, exclusive of the associated volcanic 
rocks. The uppermost mass consists of limestone,, which some- 
times acquires the enormous thickness of seven or eight hun 
dred feet, below which is a series much inferior in thickness, 
consisting of a calcareous sandstone, conglomerate and schistose 
limestone, and beneath this again, blue marl. The whole of 
the above groups contain shells and zoophytes, nearly all of 
which are referrible to species now inhabiting the contiguous 
sea. 
Castrogiovanni. 
No. 5. 
p0->. 
Syracuse. 
Girgenti. 
— ^^Xc 
a, Great limestone of Val di Noto. 
b, Schistose and arenaceous limestone of Floridia, &c. 
c, Blue marl with shells. 
d, White laminated marl. 
e, Blue clay and gypsum, &c. without shells. 
Great limestone formation (a, diagram No. 5). — In mineral 
character this rock often corresponds to the yellowish white 
building-stone of Paris, well known by the name of Calcaire 
grossier, but it often passes into a much more compact stone. 
In the deep ravine-like valleys of Sortino and Pentalica, it is 
seen in nearly horizontal strata, as solid and as regularly bedded 
as the greater part of our ancient secondary formations. It 
abounds in natural caverns, which, in many places, as in the 
valley of Pentalica, have been enlarged and multiplied by ar- 
tificial excavations. 
