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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 

 fishes' teeth and palates, unknown in the overlying 



