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 f. 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, o 1 uring a 

 short excursion in Ischia, 28 species of shells, all of which, 

 with one exception, were identified by M. Deshayes with recent 

 species J. 



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, 

 intcrstratified with some deposits of clay, free from any inter- 

 mixture of volcanic matter. These clays might have re- 



* Geol Trans., vol, ii. part iji. p. 351. Second Series, 

 t Scrope, ibid, J See the list of these (shells, Appendix IJ, 



