1848.] MURCHISON ON THE STRUCTURE OF THE ALPS. 269 



coralline bodies, which occasionally weather out on the surface. 

 M. Pilla compares this rock with the lower ammonitic or liasso- 

 jurassic limestones of Como, and he cites the fossils as pertaining to 

 the genera Cardita, 3Iodiola, Pecten, Terebratula^ but does not 

 name the species. 



A transverse section of the western promontory, from the gulf 

 south of La Spezia by the hills of Corregna to Campiglia, exhibits a 

 great line of fracture *, irregularly parallel to the ridge, along which 

 the highly twisted beds of dark-coloured limestones and schists (4) 

 have been snapped asunder, and by which a portion of the Porto Ve- 

 nere series is thrown into an inverted position, and seems irregularly 

 to overlap a series of strata which are unquestionably of younger age. 

 These are, first, grey limestones and dolomites, dipping to the N. and 

 S. of E. at 45°, followed by schists, shale, and very thin-bedded, finely 

 laminated red and grey limestone, the angle of inclination in which 

 increases gradually to 70° E.N.E. and E. It is in this group, par- 

 ticularly in certain red and grey limestones, that most of the ammo- 

 nites and other peculiar fossils of La Spe2ya occur, which have been 

 enumerated by Sir H. De la Beche. 



The above fossil zone is underlaid by rotten schists with sandy 

 rotten limestone, and then by numerous alternations of green and grey 

 limestone, whitish calcareous grits, purple and white and red schists, 

 in parts almost jaspideous, with courses of whitish limestone, the 

 whole (5) in very thin-bedded strata, in which unluckily no fossils 

 have been discovered. This calcareous series is flanked by a wall of 

 sandy and pebbly conglomerate, on which stands the lofty village of 

 Campiglia ; and the beds, after first positively underlying all the 

 older series at an angle of 80°, first become vertical, and then dipping 

 away to the west form the base of all the hills of fine macigno sand- 

 stone. This conglomerate and the associated macigno are thus seen 

 to partake intimately of the same great elevations and flexures which 

 have affected the older limestones in the Apuan Alps and in the gulf 

 of La Spezia. 



It is now well known that the macigno of this tract, which, both 

 from mineral character and order of superposition, was formerly taken 

 by geologists for the most ancient, is in fact the youngest of this series ; 

 but whether it represents a portion of the cretaceous system, or is 

 younger, is, in the absence of all fossils, still doubtful. That this 

 macigno is in an inverted position is also noticed by Pilla f. In enu- 

 merating the list of fossils of the upper Jurassic at Corregna, that 

 author mentions Ammonites Tatriciis and Nerincea (the former I 

 found myself), and I have therefore no doubt that this band repre- 

 sents the "ammonitico rosso" or Oxfordian of the Alps, and that 

 the masses intercalated between it and the macigno are probably im- 

 perfect and non-fossiliferous equivalents of some member of the cre- 

 taceous rocks. 



* M. Collegno sent a memoir on La Spezia to be read at the meeting of the 

 Scienziati Italiani of Venice, 1847, in which he indicated a great hne of fault par- 

 allel to the strike. He afterwards explained his \aew of the phaenomenon to me. 



t Bull, de la Soc. Geol. de France, vol. iv. p. 1069, section pi. 6. fig. 2. 

 VOL. V. — PART I. U 



