294 Geological Society. 



characteristic structure, associated with others of a more slaggy and 

 scoriaceous type, occurred repeatedly in the overlying beds up to 

 the base of the Cambrian, described by Prof. Hughes and Dr. Hicks, 

 the felsite pebbles in which come from the same source. 



Lastly, he showed that the signs of metamorphism and apparent 

 " melting down " asserted to be visible on the sides of Llynn Padarn, 

 proved, on microscopic examination, to be mainly superficial. 

 Hence he maintained that these rocks were rhyolitic lava-flows of 

 Pre-Cambrian age. 



5. " On the Metamorphic Series between Twt Hill, Caernarvon, 

 and Port Dinorwic." By the Eev. Prof. T. G. Bonney, M.A., F.R.S., 

 F.G.S., and F. T. S. Houghton, Esq., B.A. 



In the Geological-Survey map this district is coloured as " intru- 

 sive felsite," together with those spoken of in the last paper. It 

 was asserted to be probably metamorphic rock by Prof. Hughes and 

 Dr. Hicks in a communication made to the Society last year ; and 

 the first author confirmed that view by microscopic examination of 

 a specimen collected by them. ■ The authors had during the past 

 autumn more minutely examined the district, and found : — (1) that 

 the general character of the series was that of a metamorphic one ; 

 (2) that the rocks of granitoid aspect were associated with well- 

 marked beds of conglomerate ; (3) that this series extended up to a 

 little beyond Port Dinorwic, where the quartz-felsite set in. The 

 paper described the microscopic structure of some of the rocks ; and 

 the author expressed the opinion that the more granitoid specimens 

 were probably the results of alterations of felspathic grits. 



Feb. 21.— Henry Clifton Sorby, Esq., F.R.S, President, in the Chair. 

 The following communications were read : — 



1. A copy of a Letter from the late Acting Governor of the Falk- 

 land Islands, relating to the overflow of a peat-bog near Port Stan- 

 ley, in East Falkland. 



2. " Note on PoiJcilojoleuron BucJclandi, of Eudes Deslongchamps 

 (pere), identifying it with Megalosaurus BucMandir By J. "W. 

 Hulke, Esq., F.B.S., F.G.S. 



3. " Note on a Femur and a Humerus of a small Mammal from 

 the Stonesfield Slate." By H. G. Seeley, Esq., F.L.S., F.G.S., Pro- 

 fessor of Geography in King's College, London. 



4. "A Review of the British Carboniferous Fenestellidse." Bv 

 G. W. Shrubsole, Esq., F.G.S. 



March 12. — Henry Clifton Sorby, Esq., F.P.S., President, in the 



Chair. 



The following communications were read : — 



1. "On Perlitic and Spherulitic Structures in the Lavas of the 

 Glyder Fawr, North Wales." By Frank liutley, Esq., F.G.S. 



The rock, to the eye and under the microscope, has all the appear- 

 ance of a felstone, but under the latter also exhibits perlitic structure 

 as clearly as one of the Saxony perlites. Some of the other felstones 

 of the Glyder Fawr show numerous spherulites. These felstones 

 have been determined by the Survey to be lavas of Bala age. 



