1849.] SHARPE ON THE SECONDARY ROCKS OF PORTUGAL. 143 



Some insignificant and nearly horizontal beds of limestone are seen 

 interstratified with the sands near Mamarosa, about three leagues 

 from Aveiro on the road to Coimbra ; in these were found 



Pecten quinquecostatus, Sow. Diadema Lusitanicum, n. s. 



Exogyra conica, Sow. 



The first two, being common in the north of Europe in the upper green- 

 sand, show us that the limestones of Mamarosa belong to the upper- 

 most part of the subcretaceous series. Below the limestones there is 

 a repetition of coarse ferruginous sands and incoherent sandstones, 

 all of which might be easily confounded with the modern gravel but 

 for the guide afforded by the fossiliferous beds of limestone. 



The position of the beds along this part of the country will be 

 seen in section No. 1 (fig. 2), drawn from iVveiro to Coimbra. 



At Vendas Novas, four leagues N.W. of Coimbra on the Aveiro 

 road, and also at Mealhada, three leagues north of Coimbra on the 

 Oporto road, beds of a grey argillaceous limestone, nearly horizontal, 

 are seen below the sands of the subcretaceous series ; these limestones 

 contain fossils of the age of the lias which will be enumerated in their 

 place ; the limestones are of no great breadth, and on passing them 

 we find again the same slightly ferruginous sands, occasionally con- 

 taining some insignificant beds of limestone, which continue to the 

 village of Sarjento-mor, about six miles north of Coimbra, where 

 several thin beds of limestone, very full of shells, crop out with a 

 slight dip N.W., resting on a loose sandstone. 



The species found at this spot are the following : — 



Exogyra conica, Sow. Nerinsea Conimbrica, n. s. 



Pecten sequicostatus, Lam. Tylostoma ovatum, n. s. 



Plicatula pectenoides, Sow. globosum, n. s. 



Natica bulimoides, Leymerie sp. • punctatum, n. s. 



Nerinaea cylindrica, Voltz. 



The first four species in this list are well-known shells of the green- 

 sand, and the first-named two species of Tylostoma are common in 

 all the upper portions of the subcretaceo\is beds of Portugal, and are 

 also found in the hippurite limestone at Lisbon ; so that we may 

 safely refer this limestone to the upper portion of the subcretaceous 

 series, notwithstanding the presence of the Nerincea cylindrica, which 

 in Germany is found in the Kimmeridge clay. 



This bed of limestone continues towards the S.W., and was seen 

 again in that direction at San Fagundo, where I collected 



Tylostoma ovatum, n. s., Tylostoma Torrubise, n. s. ; 

 globosum, n. s., 



from thence it is probably continued southward to Condeixa, which 

 stands on a horizontal bed of similar limestone, containing 



Tylostoma ovatum, n. s., Tylostoma Torrubiae, n. s. ; 



at both these two places the shells of the genus Tylostoma are ex- 

 cessively abundant. 



Both at Condeixa and Sarjento-mdr the bed of hmestone just men- 



