288 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DcC. 13, 



stones and conglomerates, whilst in Italy they are soft marls and 

 sands. 



The true pliocene deposits of Asti occupy a broad trough, watered 

 by the rivers Tanaro and Bormida, on the southern side of which rise 

 up those micaceous and often greenish sandstones of miocene age, 

 so largely displayed in Piedmont. On a former occasion (1828) I 

 traversed a large breadth of these between Savoua and Acqui in the 

 company of Sir C. Lyell, and in my last visit I examined them in 

 travelling to Genoa from Alexandria. Between Gavi and Arquata, 

 they have all the characters of a regenerated macigno, and at Ser- 

 ravalle and Ligurosa rise up from beneath the subapennine marls 

 and sands in highly inclined sandstones and marls, underlaid by 

 powerful bands of conglomerate that dip 40° to the N. or N.N.W. 

 In this manner we reach the opposite or southern side of the 

 great tertiary trough of the Astesan, and are again in the equiva- 

 lents of the Superga conglomerate. I could discover, however, no 

 course of underlying nummulitic limestone similar to that of Gassino. 

 At the same time it must be stated, that the system of macigno and 

 alberese, which is considered by Pareto to be the equivalent of the 

 nummulitic group (?), succeeds near Ronco, dipping at a high angle 

 under the whole of the conglomerate and miocene series of Piedmont. 

 I cannot positively say whether these underlying beds of flagstone and 

 macigno on the south side of the basin are conformable to the over- 

 lying miocene series, but in a rapid survey they seemed to me to be 

 so, and also to be in a much less crystallized and altered state than 

 in the en\drons of Genoa. 



The miocene of Piedmont containsthe coal deposits of Caddibuona*, 

 so long known and so often described, on account of the remains of 

 the Anthracotheria associated with lacustrine and fluviatile fossils ; 

 and as we travel down into the peninsula similar examples are met 

 with. The interstratification of freshwater or estuary beds (containing 

 Melanopsis, Melania and Neritina) with marine tertiary strata, has 

 been pointed out as occurring in several parts of the north of Italy by 

 the Marquis Pareto f. Near Siena, as will presently appear, such 

 beds manifestly inosculate with the upper strata of subapennine age ; 

 whilst in the environs of Tortona they seem (judging from that 

 author's section and description) to lie low in what must be defined 

 as the true pliocene formation. The fact, however, is, that as some 

 of the acknowledged miocene strata of the peninsula are of ter- 

 restrial and freshwater character (Caddibuona, Monte Massi and 

 Monte Bamboli in the Maremma, &c.), there can be little doubt, 

 that the more observation is extended, the move evidences shall we 

 find of such local freshwater intercalations throughout the tertiary 

 series in many parts of Italy. 



* I visited this place with Sir C. Lyell, in passing from Savona to Acqui. Its 

 powerful conglomerates are possibly of the same age as those of the Superga (see 

 Lyell's Principles of Geology, 1st edition, vol. iii. p. 221, woodcut No. 55, and 

 4th ed. id. vol. iv. p. 152). 



t See the Marquis Pareto's memoir, read at the Scientific Congress of Turin, 

 1844, entitled " Sopra alcune alternative di strati marini e fluviatili nei terreni di 

 sedimento superiore dei Colli Subapennini." 



