1849.] SHARPE ON THE SECONDARY ROCKS OF PORTUGAL. 167 



Mondego limestone, as we rise from limestones and marls full of 

 Ammonites to a series of marls and sandstones, including several beds 

 of coal and containing land plants, but without any remains of marine 

 animals. And in the beds above this carboniferous series the organic 

 remains present a complete contrast to those seen in the beds below 

 the coal, being of the genera Ostrcea, Perna, BianchorUy Corbula, 

 and Mytilus; all probably inhabitants of moderate depths, with only 

 one species of Terebratula and no Cephalopod whatever. To these 

 succeed coarse sands and grits, which, like the Mollusca just men- 

 tioned, indicate the existence of a shallow sea at a moderate distance 

 from land. And this is the character of all the subsequent deposits, 

 excepting the great calcareous formations of Coimbra and Monte 

 Junto, containing Ammonites and Belemnites^ which were probably 

 formed in deeper water. 



The whole of the rocks of the subcretaceous series appear to have 

 been formed near the land and in shallow water. The limestones in 

 this series bear only a small proportion to the sandstones. In the 

 lower division there are large accumulations of corals, which are so 

 abundant at Alenquer and in the corresponding beds between Alhandra 

 and Sobral as to form complete reefs : the species of Ostracece, Car- 

 dium, Mytilus, &c., together with Gasteropoda often of large size, 

 also indicate deposits in seas of moderate depth, and the bed of lig- 

 nite found in several localities proves that land was then not far distant. 

 The negative evidence is to the same effect ; in these beds I only 

 found one specimen of Belemnite and not a single Ammonite, while 

 the Terebratidce are very rare and confined to the lower part of the 

 series. 



The hippurite limestone mth subordinate beds of calcareous marl 

 appears to have been formed in quieter water, but the organic remains 

 found in it indicate that it was deposited in a sea of moderate depth : 

 they are principally Lamellihranchiata, Gasteropoda, and Rudista, 

 without any Cephalopoda or Brachiopoda. 



Thus after the deposition of the older Jurassic limestones nearly all 

 the secondary rocks of this district appear to have been deposited in 

 shallow waters, and for the most part in rough seas near a coast. But 

 we cannot appreciate all the bearings of these facts till we know the 

 characters of the formations of the same age in other parts of the 

 Peninsula. 



The proportion between the new and the previously knovra species 

 of organic remains is very different in the different secondary forma- 

 tions of Portugal : in my collection only about 45 per cent, of the 

 fossils from the hippurite limestone are described species, in the sub- 

 cretaceous beds 53 per cent., and in the Jurassic series about 84 per 

 cent. As the species of secondary European fossils hitherto described 

 are nearly all from the north and middle of Europe, the proportion 

 of described species in a Portuguese formation shows how many of 

 the species are known to have been common to the seas of the north 

 and south of the Pyrenees at the geological epoch in question. 



Before we can safely conclude from the above statement that the 



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