298 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 13, 



as these lignites are manifestly posterior to any stratum of the num- 

 mulitic series, which I regard as the eocene of Southern Europe, I 

 must consider them to be of miocene age, though in some instances 

 representing perhaps the lower beds of that division. In the full and 

 consecutive marine series of the Monferrato, and in the Apennines 

 of Bologna, no doubt can remain of a perfectly equable and confor- 

 mable transition from miocene into pliocene. Even in the convulsed 

 region of the Tuscan Maremma and its flanks, it is manifest that 

 beds of miocene are surmounted by the whole series of the lower 

 gypseous marls, which in their turn, though often highly inclined, 

 pass up into true subapennine blue marl. 



Some geologists have indeed endeavoured to distinguish the miocene 

 from the pliocene tertiaries of Italy by the inclination of the strata in 

 the one and their horizontality in the other. But this method is 

 fallacious ; for although the great shelly masses of pliocene age, which 

 occupy broad valleys or large troughs, are necessarily more or less 

 horizontal, wherever they are removed from centres of disturbance, 

 there are numerous districts in which they are highly inclined. Thus, 

 without going back to the sections of Bassano, the Monferrato, Bo- 

 logna, &c., we see both the blue marl and yellow sands, which are so 

 horizontal along the banks of the Elsa in Tuscany, dip at 35° to the 

 east of Yolterra, whilst they are followed downwards at Specchiajolo 

 and Pignano, on the road to Colle, by gypseous marls, which are still 

 more highly inclined as they approach a ridge of elevation. Again, 

 where the basaltic cone of Radicofani perforates the tertiary trough 

 of blue marls which lie between the ridges of Monte Amato on the 

 west and Monte Cetona on the east, these young strata are singularly 

 dislocated. Even without quitting the environs of Rome, the most 

 perfect horizontality of the blue marls and overlying sandstones may 

 be observed near St. Peter's and the Vatican ; and yet in following 

 the uppermost of these strata to the summits of Monte Mario or west- 

 wards towards Civita Vecchia, they are found to undulate so rapidly 

 with local breaks, that sections made in two detached spots would 

 show an apparent unconformity, when in fact all is one continuous 

 series. 



On the shores of Italy, as in the valleys of the Arno and the Tiber, 

 there are many proofs of a succession of deposits similar to that 

 which has been alluded to near Rome, ascending from the subapen- 

 nine or pliocene sera into the period when all the sea shells found in 

 the raised beaches are those of the present sea. On this point I will 

 now only add, that the oscillation to which the coast has been sub- 

 jected in the historic period, when the temple of Serapis in the bay of 

 Puzzuoli was depressed about twenty-five feet below its present level 

 and afterwards raised, was by no means a mere local subsidence, but 

 one which affected the whole of the adjacent coast of Italy. For, on 

 the seaward face of the promontory of Gaeta, which is a mass of sub- 

 crystalline or hippurite limestone, I satisfied myself of the accuracy of 

 the observation of Pilla* and other Italian geologists, that pholades 

 of existing species had eaten into the rock at about the same height 



* Trattato de Geologia di L. Pilla, vol. i. p. 334. Pisa, 1847. 



