140 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr. 6, 



in certain beds, and Pecopteris abounds in others : only one specimen 

 of Sigillaria bas been met with. 



Only one fragment of a Pecten lias been found in a yellow 

 clay belonging to the beds just described ; and they contain no Ume- 

 stone. 



The carboniferous beds usually strike N. and S. and dip W. from 

 30° to 35°, with the least dip in the upper beds ; but there are spots 

 where the strike is from N. 26° E. to S. 26° W., and between Villa 

 de Monsarres and Algeris the dip is between 40° and 70° to the E. ; 

 but these are local accidents. For three-quarters of a league, between 

 Fonte do Salgueiro and Passo, the carboniferous beds rest uncon- 

 conformably on the fossiUferous Silurian rocks ; but to the north 

 and south of those places they overlie cliloritic and micaceous schists 

 or old unfossiliferous clay-slates. The chloritic and micaceous schists, 

 between Villa Nova de Monsarres and the Convent of Bussaco, have 

 been elevated subsequently to the deposition of the carboniferous beds, 

 which are disturbed and broken through by the schists ; but the red 

 sandstone does not participate in the effect of this movement. 



For one league from Linho de Matta near Larcao, to the Fonte do 

 Salgueiro, and also from Villa Nova de Monsarres to the parallel of 

 Junqueira, the carboniferous beds are covered unconformably by red 

 sandstone ; in other places they lie in isolated patches on the schist- 

 ose rocks. 



The principal materials of tiie carboniferous beds are from the 

 debiis of granite and similar rocks. 



In referring this series to the Coal-formation, it is rather to be 

 compared to that formation in France and England than to the ma- 

 rine Coal-foi'mation of the Asturias. As it is partly concealed by 

 the overlying new red sandstone and subcretaceous sands on the 

 west, and only shows a zone A'arying from 200 to 800 meti-es in 

 width of its lower or eastern portion, there may be a greater thick- 

 ness of the formation concealed to the westward under those over- 

 lying formations, in which valuable beds of coal may still be 

 found*. 



Silurian Formations. — The Silurian rocks rise from below the 

 carboniferous conglomerates above described, from Passo to the Fonte 

 do Salgueiro, vrith a general direction of N.W. to S.E., and form the 

 principal part of the Serra de Bussaco ; they begin at the northern 

 extremity of that ridge and extend towards the south for five or six 

 leagues, crossing the river Mondego at Pena Cova ; they cover a 

 breadth varying from two to three miles, and have a thickness of 

 more than 2500 metres. These beds admit of a division into three 

 principal groups, of which the two lower divisions belong to the Lower 

 Silurian series, and the upper may perhaps be of the age of the Wen- 

 lock or lower portion of the Upper Silurian beds of England. 



Lowest Division {Lower Silurian) . — This, which forms the principal 

 part of the formation and occupies the eastern half of the Silurian 

 district, is composed of quartzites, micaceous sandstones, white, yel- 



* Senhor Ribeiro's arguments in favour of finding Coal below the Red Sand- 

 stone being of a very theoretical character and of local interest, they have been 

 abridged very much in the text.— D. S. 



