1849.] SHARPE ON THE SECONDARY ROCKS OF PORTUGAL. 1,55 



Thin-bedded sandy limestone with shells. 



Sand and sandstone ; at Verandas. 



Sand and marl with some beds of limestone ; at Carnota. 



Coarse white limestone at Refugidos ; the lowest bed of the section. 



The following species were found in the limestone at Alenquer : — 



Cidaris clunifera, Agassiz. Nerinaea Bruntrutana, Thurman. 



glandifera, Goldfuss. gigantea, D^ Hombres-Firmas. 



Nerinaea annulata, n. s. grandis, Voltz, not of Goldfuss. 



The following were found in the calcareous beds below the iVlenquer 

 limestone, between two and three miles south of that town : — 



Nerinaea turbinata, n. s. Corbula compressa?, D^OrMgny. 



Nerita turbinata, n. s. Cyprina securiformis, n. s. 



Neritina bicornis, n. s. Perna polita, n. s. 



We must refer to the same bed the two great ridges of coralline 

 limestone crossed on section No. 5 (fig. 6), the more eastern of which 

 runs northward from Villa Franca through Alenquer, passing a little 

 west of Otta, and continuing to Alcoentre ; the other commencing on 

 the Tagus on the south side of Alhandra and forming the line of Wel- 

 lington's defences to Sobral : their position, dipping in opposite direc- 

 tions away from a common axis, their identity of mineral character, 

 and the similarity of their organic contents, which in both cases con- 

 sist principally of corals of which several of the species are the same, 

 all show the identity of these limestones. Therefore in looking at 

 the fossils with the view of settling the age of the deposits, we may 

 unite the above lists with those at p. 154, and consider the whole to- 

 gether. 



The lists present us with a most unusual assemblage of shells ; of 

 which 



Natica praelonga, Deshayes, Corbula compressa, IfOrhignyj 



Sphaera corrugata, -Sow., Cidaris clunifera, Agassiz, 



Nerinaea gigantea, D^ Hombres-Firmas, 



are only hitherto known in the lower greensand ; and to these Neri- 

 ncEa turbinata will probably have to be added as a greensand species. 



Cardiura dissimile, Sow., Gervilia aviculoides. Sow., 



have been fomid in England both in the lower greensand and in the 

 Portland oolite. 



Nerinaea Bruntrutana, Thurman, Nerinaea grandis, Voltz, not of Goldfuss, 



have been found in the Portland oolite. 



Cidaris glandifera, Goldfuss, Perna rugosa, Goldfuss, 



usually belong to the great oolite. 



Notwithstanding the admixture of oolitic species, those of the green- 

 sand predominate, and lead me to class these beds in the subcreta- 

 ceous series. The position and character of the beds also are in fa- 

 vour of the same view. They agree so closely in mineral character 

 and underlie in so regular a sequence the rest of the subcretaceous 



