ON THE TERTIARY FORMATIONS OF SPAIN. 5 



sionally according to the undulating nature of the hills on which they 

 were deposited. 



The following is the order of the beds in ascending series, the lower- 

 most lying irregularly on granitic, porphyritic and cretaceous rocks. 



1 . A bed of blue and yellow clay, 2 or 3 varas thick, without fos- 

 sils, but occasionally containing thin beds of impure lignite. 



2. A bed of yellow calcaire grossier, sometimes marly, containing 

 whole and broken fossils, amongst which are the genera Venericar- 

 dium, Ostrea^ Conus, Pecten, Mytilus, Trochus, Turritella, Balanus, 

 Clypeaster, besides claws of crabs, fragments of madrepores and other 

 zoophytes. Its thickness is not more than 10 or 12 varas near Tar- 

 ragona, but it sometimes exceeds 70 at no great distance, where the 

 characteristic fossils are Cotius deperditus of Lam., and C. Noe of 

 Brocchi. It is used as a building-stone, although easily destructible. 



3. A white siliceous formation of white sand, without fossils, 2 or 

 3 varas in thickness. 



4. Another sandy bed, resembling the former, with the same spe- 

 cific characters, differing only in colour, inasmuch as this is yellow 

 and somewhat harder. 



5. A bed of oysters connected by an argillaceous matrix. Amongst 

 these, O. giganteus is most remarkable. 



6 . A white hard siliceous limestone with conchoidal fracture, earthy, 

 and from 1 5 to 20 varas in thickness, the prmcipal feature of which 

 is its containing many sharks' teeth, as well as the palatal bones of 

 the same fish. 



7. Another sandstone, the calcareous grains of which increase in 

 size until it becomes a conglomerate. Its thickness is from 6 to 10 

 varas. It occurs in the upper part of the city of Tarragona, and was 

 used in the construction of the ancient Cyclopean walls. 



8. and lastly. A transported diluvium, more or less considerable 

 and cemented together, but which, from its connexion with the other 

 rocks, may fairly be considered as belonging to the same period. 



The remaining thickness necessary to make up the above-mentioned 

 150 varas consists of beds of gypsum occasionally interposed between 

 the second and third beds. 



It is not unusual to find some of these beds wanting, the thickness 

 of the others being increased. Along the coast the fossiliferous cal- 

 caire grossier generally lies upon the chalk, and is covered over by 

 the conglomerates. 



The best section of the tertiary formation of Tarragona is from the 

 Puerta del Milagro, or Fuerte della Reina, on the east of the city 

 towards the landmarks on the heights half a league distant between 

 the Fuerte del Olivo and the ruined palace of Lorito. 



An extensive tertiary formation occurs proceeding south from the 

 Sen de Urgel, stretching by the mountain of Montsec, and then turn- 

 ing west into the Conca de Tremp, and east towards the flanks of 

 Montserrat. Extending to the south it covers a large portion of the 

 province of Tarragona, a considerable part of which was formerly 

 occupied by a large freshwater lake, according to the fossils found 

 therein {Paludina^ LimnceuSj Planorbisj Nerita [Neritina'^.'], HeliXj 



