268 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 13, 



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surmounted by a quartzo-scliistose mass. (2), which 

 presents the aspect of havhig undergone a metamor- 

 phosis which has affected the hard purple schists, the 

 conglomerate or pebbly beds, and the green schists 

 above them, the latter being traversed in many di- 

 rections by white veins of carbonate of hme. This 

 mass (2), not less than 300 feet thick, is amorphous, 

 and in colour partially resembles serpentine*. After 

 passing a portion of the cliff which is obscured by 

 detritus, a dark or almost black limestone with white 

 veins appears, undulating irregularly, and plunging 

 on the whole to the west and by north. This rock 

 is covered by dark schists, the Avhole probably re- 

 presenting the dark limestone and schists of Porto 

 Venere on the opposite side of the bay. These thin- 

 bedded dark masses are followed by the remarkable 

 rocks which constitute the sea-worn, amorphous and 

 cavernous rauch-kalk on which the picturesque old 

 town of Porto Telaro is built. From this point, 

 passing to the fort of St. Bartolommeo, there are 

 undulations and breaks in lower and obscurer cliffs, 

 in which the thin-bedded siliceous schists (slates of 

 Stazzemma) appear here and there beneath the rauch- 

 kalk. All the calcareous rocks of this series are 

 flanked by a vertically twisted and confused, coarse 

 conglomerate, made up of lumps of all the above- 

 mentioned rocks. 



I have spoken of this highly modified range on the 

 east side of the gulf to show its lithological accordance 

 with the chief masses in the Apuan Alps, and because 

 it exhibits the same order of succession of mineral 

 masses. It is however only on the western shores of 

 the bay, in another parallel undulation of these lime- 

 stones, further removed from the chief axes of dis- 

 turbance, that their age can be read off by help of 

 some imbedded fossils. The black limestones, with 

 white and yellow veins and associated dark schists 

 (No. 3), but not so metamorphosed as on the east 

 side of the bay, form the chief nucleus of this western 

 promontory. Ranging in highly inclined and vertical 

 forms, by the lofty, unfinished fort of Castellana, 

 they strike from N.N.AY. to S.S.E., into the isle 

 of Palmaria, where they are largely quarried as the 

 black and brown marble of Porto Yenere. Among 

 the fossils in this rock I procured a Lima, which re- 

 sembles a lower secondary fossil, and certain imperfect 



* I could not help suspecting the contiguity of some erup- 

 tive rock to this pecuhar limestone, and my boatman assured 

 me that \Yhen the sea was lower cuie of my predecessors had 

 discovered a pohit of porphyry. 



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