1849] SHARPE ON THE SECONDARY ROCKS OF PORTUGAL. 149 



pears to be a repetition of the country lying to the south-west of 

 Aveiro, and probably belongs Uke that to the uppermost part of the 

 subcretaceous group. Between Leiria and Redinha, the road from 

 Lisbon to Oporto crosses similar beds of ferruginous sand. Thus we 

 have here lost the fossiliferous limestones seen on the north bank of the 

 Mondego, and seem to begin again at the top of the subcretaceous series. 



Leiria stands on a mass of trap which has thrown up and altered 

 the beds in contact with it. On the east side of the town a bed of 

 limestone, dipping E. 45°, rests on the trap. 



Eastward of Leiria is a continuation of the ferruginous sands and 

 gravels for about four miles, where they overlie a limestone nearly 100 

 feet thick, dipping N.W. 5°, and containing Exogyra plicata. Lam., 

 Ostrcea, &c. Eastward of this for several miles the country consists 

 of hills of coarse sand, gravel, and sandstone, with some few beds of 

 limestone. Towards Aldea da Cruz and Ourem the limestones are 

 rather more important, dipping westward 2° or 3°. The old town of 

 Ourem stands on a conical hill of sand and gravel capped by a bed of 

 compact white limestone nearly horizontal, and containing 



Exogyra plicata, Lam. Cidaris. 



Mytilus ornatus, VOrh, 



The gravel below the limestone exactly resembles the modern su- 

 perficial drift which covers the low country near the sea, but for- 

 tunately the overlying limestone with its cretaceous fossils preserves 

 us from error on this head, and enables us to estimate the age of other 

 similar gravel beds in the district. 



For five or six miles farther east are beds of ferruginous sand, 

 similar to those so often described, containing some insignificant beds 

 of limestone, and dipping W. 3°. 



The preceding series rests on the Jurassic rocks of the great lime- 

 stone chain already mentioned, which here dip E.S.E. 10°, consisting 

 of a compact white limestone of great thickness, resting on soft ferru- 

 ginous sandstones alternating with limestone, which latter beds are 

 but slightly exposed on the western flank of the chain. The section 

 No. 3 (fig. 4) explains the position of the beds along the line just 

 described. 



From the mouth of the Mondego to the boundary of the forma- 

 tion beyond Ourem, we appear to have a gradually descending series 

 of beds ; but from their very slight inclination they may be of no 

 great total thickness, notwithstanding their covering a considerable 

 extent of country : the whole appear to belong to the upper part of 

 the subcretaceous series. The Exogyra plicata here takes the place 

 of the Exogyra conica, which is so abundant north of the Mondego : 

 as we proceed southward we lose the latter species, and the E. plicata 

 becomes more abundant, and is throughout a large district round 

 Lisbon the most characteristic shell of the cretaceous and upper half 

 of the subcretaceous series. 



To the south of Leiria the principal rock is still a coarse ferrugi* 

 nous sand, but the alternations of limestone are more frequent ; all 

 the beds are much disturbed, and there are frequent changes of dip, 



VOL. VI. — PART I. M 



