This opinion I
expressed after my visit to Italy in 1828 (See 1st edition of Principles of
Geology volume 3 chapters 8 and 14 1833 and former editions of this work chapter
31.), and it has recently (1850) been confirmed by the argument adduced by Sir
R. Murchison in favour of the submarine origin of the tertiary volcanic rocks of
Italy. (Quarterly Geological Journal volume 6 page 281.) These rocks are well-
known to rest conformably on the Sub-apennine marls, even as far south as Monte
Mario, in the suburbs of Rome. On the exact age of the deposits of Monte Mario
new light has recently been thrown by a careful study of their marine fossil
shells, undertaken by MM. Rayneval, Van den Hecke, and Ponzi. They have compared
no less than 160 species with the shells of the Coralline Crag of Suffolk, so
well described by Mr. Searles Wood; and the specific agreement between the
British and Italian fossils is so great, if we make due allowance for
geographical distance and the difference of latitude, that we can have little
hesitation in referring both to the same period, or to the Older Pliocene of
this work.
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