1849.] SHARPE ON THE SECONDARY ROCKS OF PORTUGAL. 165 



The carboniferous beds of Cape Mondego must be compared to the 

 oolitic coal of Yorkshire : their position in the series seems nearly the 

 same, and the same species of Zamites has been found in both. 



The beds of limestone and marl below the coal belong to the lower 

 part of the oolitic series. 



The limestones of Montemdr-velho, Vendas Novas, and Mealhada 

 must be classed with the lias. 



In this list we seem to have representatives of the principal oolitic 

 beds ; yet it is probable that there are other Jurassic beds in the Pe- 

 ninsula which have no representatives in the district here described ; 

 for it has been usual to class in the oolitic system the grey limestone 

 of Gibraltar and the Ronda hills which rests on a thick formation of 

 brown shale, neither of which rocks can be compared with any of the 

 beds above mentioned. The limestone of San Pedro near Cintra has 

 more resemblance in mineral character to that of Gibraltar than any 

 other of the Portuguese limestones, but it would be premature to 

 class them together while so little is known of either. 



This comparison of the Jurassic rocks of Portugal with those of 

 England is only made in the most general sense : the rocks of the 

 two countries differ in mineral character, being in England oohtes 

 alternating with blue clays, and in Portugal hard compact hmestones 

 separated by ferruginous sands : it is only in the organic remains con- 

 tained in them that we find any true resemblance. 



Sandstones of which the age is not yet determined. 



To complete the account of my observations of the secondary for- 

 mations of this part of Portugal, it only remains to describe certain 

 beds of sandstone of undetermined age, which lie within the area of 

 secondary rocks. 



Red Sandstone of the Vouga. — Following the road from Coimbra 

 to Oporto we meet near Agueda with a coarse, friable, white sand- 

 stone dipping S.E. 5°, which passes into a softer reddish sandstone 

 and ferruginous sand which continue to within a quarter of a mile of 

 Serdao, where they dip S. 2° or 3°; these are the last beds of the 

 subcretaceous series which are seen in proceeding northward along 

 this road. 



Just before reaching Serdao, a red sandstone, dippmg S. 15°, rises 

 from below the beds just mentioned and continues with some irregu- 

 larities of dip to the north bank of the Vouga, where its continuation 

 to the northward is concealed by gravel covering the country up to 

 the appearance of the micaceous schist at Albergaria velha. 



The red sandstone of Serdao has no resemblance to any of the 

 Portuguese rocks yet described ; it is a fine-grained sandstone of a 

 deep brick-colour, in well-defined beds separated by thin layers of marl, 

 and closely resembles the new red sandstone of our Midland counties. 

 It cannot extend far to the westward of Serdao, as near the mouth of 

 the Vouga the subcretaceous sands rest immediately on the Silurian 

 rocks. I have no information respecting its extent eastward, and 

 must leave its age in doubt. Yet its position in contact with the 

 older schists being similar to that of the sandstones of Busaco and 



VOL. VI. — PART I. N 



