File:The Quarterly journal of the Geological Society of London (12645174895).jpg

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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. .Dec. 13,
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whicli succeeds to the west : for the latter is only
slightly inclined to the east, and is a hard, mica-
ceous, true macigno sandstone, which, flaglike
near the surface, passes down into thick beds.
This rock, receiving its peculiar tint from nu-
merous minute fragments of black schist, is un-
distinguishable from the macigno alpin or flysch
of the Alps. It occurs, in fact, on the western
edge of those great undulations of alberese, and
other limestones, which, perforated by serpentine
at Monte Berici and Sasso di Castro near Covi-
gliajo, form the chief mass of that group already
spoken of, whose geological equivalents in the
absence of fossils it is so difficult to define.
Thus, whilst the Bolognese Apennines expose
an intimate connection between the miocene and
pliocene groups, they aiford, as far as I saw, no
indications of an unbroken succession from the
macigno to the overlying miocene. It appeared,
indeed, to me, that in descending towards Flo-
rence by Campo Santo and Crespiano, a conglo-
merate (probably miocene) was there also adherent
to the sides of the mountains of older date ; but
in that portion of Tuscany the union between the
miocene and pliocene, as above described, is
wanting.
The picturesque hills around Lari, on the south
side of the Arno near Pisa, which I visited with
Professor Pilla, are for the most part composed
of subapennine blue marl, loaded with shells and
covered by yellow sands ; the Ostrea hippopuSy
Pecten laticostatus^ and large Panopcea Favjasi
lying about in abundance. The villages stand
on insulated points of the overlying sands or
sandy marls, the remnants of former great de-
nudations, all the strata being horizontal. These
elevated sandy and loamy points are rich and
fertile, whilst the denuded argillaceous marls of
the valleys are sterile ; — physical features which
so prevail in vast tertiary tracts throughout Italy,
that the agricultural characters alone are there
sufficient to indicate the age of the strata. Near
Casciano, however, to the south of Lari, as well
seen in the quarries of S*^ Frediana, other and
lower sandstones of harder character, rise out
abruptly from beneath the subapennine cover,
and form broken and undulating domes. These
beds contain highly ornamented small Echini,
small Ostreae, and other shells, together with