11-4! Geological Societi/. 



La Spezia by a plain through which the Magra flows. The plain is 

 covered by gravel rising to some height above the Mediterranean. Of 

 this gravel the banks ofthe Frigido aftbrd a good section. NearPonzo, 

 between La Spezia and Borghetto, a torrent cuts through a hill com- 

 posed of large rounded boulders and gravel, the coherence of which is 

 trifling. These boulders could not have been produced by any causes 

 at present existing in the district. The boulders are carried down the 

 bed of the torrent but a short distance beyond the places where they 

 occur as component parts of the hills. In the bed of the Vara, into 

 which this torrent flows, there is gravel ofthe usual size, which may 

 have been formed, and afterwards cut through, by the river. 



Stratijied Rocks. — 1. a. Lignite, clay, sandstone and conglome- 

 rate, are described as being seen in vertical strata at Caniparola, 

 near Sarzana, the shaly beds containing the Fucoides intricatus (Ad. 

 Brongn.) and the conglomerate being made up of compact limestone, 

 macigno sandstone, and jasper, cemented by clay. These tertiary 

 beds are supposed to have been thrown into their present vertical 

 position by the forces which elevated the adjoining Alpi Appuani. 



I . b. Breccia, with a porous limestone cement, is one of the 

 youngest rocks in the gulf of La Spezia, where it occurs in promon- 

 tories, and caps some of the cliffs : — from its resemblance to the 

 rauchwacke of the zechstein, it has been erroneously referred to that 

 formation. 



1. c. Siliceous sandstone is connected with the breccia above-men- 

 tioned, with which it is associated in contorted beds at St. Terenzo. 

 The author does not pronounce positively upon the relative ages of 

 the rocks of this group, although he asserts that they are all younger 

 than the macigno. 



2. Macigno. — Two sandstones of somewhat the same mineralogi- 

 cal structure, but of very different age, are comprehended under this 

 name by the Italians j but the author here restricts the term to that 

 which is highest in the order. The macigno is a brown and gray sand- 

 stone, both calcareous and siliceous, generally micaceous, with black 

 specks, and is occasionally mixed with shale. It occurs near the 

 Bagni di Lucca overlying gray compact limestone, which ranges from 

 thence into the district under consideration, and has similar relations 

 near Massa and Carrara, details and diagrams of which are given ; it 

 is also much developed north of La Spezio, and on the right bank of 

 the Magra. In the absence of organic remains, the author has not 

 been enabled to decide upon the equivalent of this rock. 



3. Gray compact limestone or Porto I'encre marble. — At La Spezia 

 this group consists of, I. Dark gray, black and yellow limestones, in- 

 terstratified with schists and argillaceous slates ; 2. Dolomite ; 3. Dark 

 gray compact limestone in thin beds; 4. Ditto with brown shale, 

 and containing Orthoceras, Ammonites, Beleranites, and round balls of 

 iron pyrites ; 5 and G. Shale, with compact thin-bedded limestone, 

 resembling that of the Jura. The islands of Tino and Paimaria are 

 composed of this system, whence it rises into the high land of La 

 Castellana, and extends to Pignone, forming the mountains of Co- 

 regna, Santa Croce, Parodi, and Bergamo. The dolomite occupying 



the 



