126 
NEWER PLIOCENE PERIOD. 
[Ch. X. 
loose lapilli. The subaqueous part may have become solid by 
an aggregative process like that which takes place in the setting 
of mortar, while the rest of the ejections, having accumulated 
on dry land when the cone was raised above the water, may 
have remained in a loose state *. 
Age of the volcanic and associated rocks of Campania. — 
If we enquire into the evidence derivable from organic remains, 
respecting the age of the volcanic rocks of Campania, we find 
reason to conclude that such parts as do not belong to the 
recent, are referrible to the newer Pliocene period. 
In the solid tuff quarried out of the hills immediately be- 
hind Naples, are found recent shells of the genera Ostrea, Car- 
dium, Buccinum, and Patella, all referrible to species now 
living in the Mediterranean j\ In Ischia I collected marine 
shells in beds of clay and tuff, not far from the summit of 
Epomeo, or San Nichola, about 2000 feet above the level of 
the sea, as also at another locality, about 100 feet below, on the 
southern declivity of the mountain, and others not far above 
the town of Moropano. At Casamicciol, and several places 
near the sea-shore, shells have long been observed in stratified 
tuff and clay. From these various points I obtained, during a 
short excursion in Ischia, 28 species of shells, all of which, 
with one exception, were identified by M. Deshayes with recent 
species \. 
As the highest parts of Epomeo are composed of regularly- 
stratified greenish tuff, and some beds near the summit con- 
tain the fossils above-mentioned, it is clear that that mountain 
was not only raised to its present height above the level of the 
sea, but was also formed since the Mediterranean was inhabited 
by the existing species of testacea. 
In the Ischian tuffs we find pumice, lapilli, angular fragments 
of trachytic lava, and other products of igneous ejections, 
interstratified with some deposits of clay, free from any inter- 
mixture of volcanic matter. These clays might have re- 
* Geol. Trans., vol. ii. part iii. p. 351. Second Series, 
f Scrope, ibid, | See the list of these shells, Appendix II. 
