138 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Nov. 21, 



side by various slaty and schistose rocks. I have already described 

 to this Society a portion of these*, which beginning on the north at 

 Esposende, line the coast as far as the Vouga, with the exception of 

 a range of crystalline rocks, of which the granite of Oporto is the 

 central axis. Near Vallongo a bed of anthracite coal underlies 

 Lower Silurian slates, which form part of this series. From the 

 mouth of the Vouga the schists run S.E., keeping on the north side 

 of that river : they then turn southward, and after running along the 

 Serra de Busaco, pass about four miles to the east of Coimbra, and 

 continue along the little river Deu9a, and then down the lower part 

 of the Zezere to the Tagus near Abrantes. The district which lies 

 between the schists just mentioned and the Atlantic, bounded on the 

 south by the Tagus, and covered for the most part with secondary 

 deposits, forms the subject of this memoir ; but before entering on 

 its description, I will carry this short summary through the South of 

 Portugal. 



Proceeding southward from Abrantes, we descend into the great 

 tertiary basin, through which the Tagus and the Sado reach the sea ; 

 this tertiary area covers between 2000 and 3000 square miles, and is 

 only interrupted by the ridge of secondary rocks extending from 

 St. Ubes to Cape Espichel. Near the sea the tertiary deposits are 

 all of marine origin, and the most important part of the series, called 

 in my former paperf the Almada beds, has been shown by Mr. James 

 Smith J to be of the miocene period. The Almada beds extend up 

 the Tagus to Verdelha ; about fifteen miles higher up the river, the 

 hills on the north bank of the Tagus, rising to a height of perhaps 

 200 feet, consist of brown marl overlaid by soft rubbly limestone, 

 containing Lymncea longiscata. Sow., a shell common to the fresh- 

 water beds of the eocene and miocene periods. I traced these beds 

 of lacustrine limestone from Cartaxo by Santarem towards Golegao : 

 they are not found near the mouth of the Tagus, and are perhaps the 

 lacustrine equivalents of the marine Almada beds. 



A little above Villa Franca I met with a bed of marl about fifty 

 feet above the present level of the Tagus, containing the common 

 Jjutraria compressa, and in the marshy flat near Villa Nova da 

 Rainha the same shell and a small variety of Cardium edule, both of 

 which now live in abundance in the estuary of the Tagus near Lisbon; 

 so that it is evident that this part of the country has been upheaved 

 at least fifty feet within a comparatively recent period. The upper 

 part of the tertiary basin forms a great marshy district, which will 

 probably prove to consist of lacustrine or fluviatile deposits of very 

 modern date. 



On the north side of Lisbon a great area is covered with basalt, 

 which separates the secondary from the tertiary formations. The 



* Quarterly Journal of the Geological Society, vol. v. p. 142. 



f On the Geology of the Neighbourhood of Lisbon. Trans, of Geol, Soc. 2nd 

 series, vol. vi. p 107. 



X On the Age of the Tertiary Beds of the Tagus. Quart. Journ. Geol. Soc. 

 vol. iii. p. 410. 



