142 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [NoV. 29, 



6. Pecopteris ? (allied to Cyathea). 



Identical with No. 7 of my Tarentaise list. The leaflets are shorter 

 and broader in proportion than in any of the forms of the Cyathea 

 group figured by Brongniart ; they vary somewhat in outline in the 

 same specimen, being sometimes nearly round, sometimes more of a 

 square form. The main stalk is always remarkably thick in propor- 

 tion to the stalks of the pinnse which proceed from it. 



7. Pecopteris ? (allied to Plukenetii). 



Identical with No. 9 of the preceding list. It is perhaps as nearly 

 allied to Sphe^iopteris latifolia of Brongniart {Aspidites latifolius, 

 Gopp.) as to Pecopt. Plukenetii ; at any rate it is one of those forms 

 which might almost equally well be referred either to Pecopteris or 

 to Sphenopteris. Venation quite undistinguishable in my specimen. 



8. Pecopteris pteroides? 



The same with No. 8 from the Tarentaise ; but the species is very 

 doubtful. 



9. Calamites 1 



Very probably one of the forms of C Suckowiiy but the species 

 cannot be determined. 



10. ASTEROPHYLLITES ? 



Apparently identical with No. 12 of the preceding list. It can 

 hardly be distinguished from some of the specimens from the coal- 

 field of Cape Breton, which I have taken for AsterophyUites foliosa. 



2. On the Geology of the neighbourhood of Oporto, including the 

 Silu7'ian Coal and Slates of Vallongo. By Daniel Sharpe, 

 Esq., F.G.S. 



On the 1 1th of April, 1832*, I laid before the Society a short notice 

 of the rocks of which the following is a more detailed account : since 

 that period I am not aware that anything more has been published 

 respecting them ; but the recent discovery of shells and trilobites in 

 the Vallongo slates has given a fresh interest to the subject. 



(A.) Crystalline Rocks near Oporto. 



The town of Oporto stands on a band of granite four or five miles 

 wide, which forms the axis of the neighbouring rocks, with a general 

 direction of about N.N.W. ; it is enclosed on each side by a belt of 

 brown micaceous schist with quartz veins, to which succeeds on each 

 side a line of granitic gneiss alternating with and passing into mica- 

 ceous and chloritic schists, which are overlaid both to the north-east 

 and south-west of the district of crystalline rocks by clay-slates of 

 sedimentary origin. In some places granite is found (as at San 

 Cosme and elsewhere) in the place of the gneiss, and there are, on the 



* Proceedings of the Geological Society, vol. i. p. 395. 



