1848.] 



MURCHISON ON THE STRUCTURE OF THE ALPS. 



285 



>• ^ 



u 



6 mass of marls and sands strikes W.S.W. and E.N.E., 

 g and that such is also the strike of the principal mass 

 S of the mottled nummulitic limestone, and of the grand 

 masses of conglomerate, sand and marl which consti- 

 tute the higher and highly inclined miocene strata in 

 the ridges of the Superga and Monferrato. 



The nummulitic limestone (^*) may be considered 



as an irregular axis, which throws off partially a few 



younger and broken beds to the north, that form the 



gypseous and other hillocks on the banks of the Po, 



. and pass under the pliocene strata of Verrua and 



S Crescentino ; whilst it is manifestly succeeded on the 



•S south by the whole ascending series of the Superga 



■^ and Monferrato. 



It is also equally clear that this nummuhtic rock 



is truly tertiary, if we judge from the other fossils 



I associated with the Nmmnidina placentula (Desh.). 



"S Thus, the terebratula on which Collegno reckoned as a 



S proof of cretaceous age, is now known to be a common 



I species of the older tertiary of this tract. In this very 



limestone we found the great oyster, O. gig ant ea, 



fragments of pectens and corals, and above all the 



tooth of a fish {Oxyrhina Desori^ Ag.), all well-known 



tertiary forms. Again, in the sandy beds, absolutely 



resting on those dislocated limestones, the Pecten Bur- 



digalensis with Pectunculi and Turbinolise occur, and 



there is therefore no sort of doubt of the age of the 



rock. 



I was much struck with the resemblance of the 

 mottled, concretionary and coralline limestone of Gas- 

 sino to the rock of Castel-Cucco between Asolo and 

 g Possagno, which is also the uppermost limit of num- 

 ^.2 mulites (p. 222). I therefore consider, that in con- 

 necting the nummulitic base of the section of the 

 Superga with a well-known band in the clear succession 

 on the flanks of the Venetian Alps, I establish a con- 

 necting link between the eocene deposits of the Alps 

 and the miocene of northern Italy. 



In traversing southwards to Bardassan, across the 

 ridges of conglomerate, both coarse and fine (A), which 

 g occupy the chief summits, and separate the valleys 

 j| excavated in the softer marl or sandy shale, I had 

 I little to observe that is not already known ; for these 

 j| elevations and depressions are the direct eastern pro- 

 longations of the miocene of the Superga ; but in 

 descending from the hills to the south by Castel Mont- 

 alto to the plain of Chieri, the development of the 

 strata and the gradual change from the miocene into 

 the pliocene type is too remarkable not to be specially 

 noticed. On the south slope of the hill of Bardassan 



VOL. V. PART I. X 



