27 



gault itself beneath the upper green-sand is again distinct in the 

 Vale of Wardour, and throughout the entire range from thence to 

 Norfolk. 



The only places in which the author has detected the presence 

 of the freshwater beds succeeding the lower green-sand, are in the 

 Vale of Wardour, and in the vicinity of Aylesbury : and it would 

 appear that the great extent of the sands immediately beneath 

 the chalk, shooting out beyond the subjacent strata, and concealing 

 their outcrop, may be one cause why the group next in succession 

 is but rarely visible in the interior ; — though it is also probable that 

 strata produced at the bottom of freshwater-lakes, or of sestuaries, 

 were originally deposited in detached portions, comparatively of no 

 great extent. 



In the Vale of Wardour, the series consists of, — 1. Chalk; 2. 

 Upper green-sand ; 3. Gault ; 4. Traces of the lower green-sand 

 (Shanklin sands) ; 5. Traces of the Hastings sands ; 6. the Purbeck 

 strata, — containing in great abundance freshwater shells, principally 

 of the genus Cyclas, and in the upper part the Cypris faba : which 

 remarkable fossil therefore pervades the whole group between the 

 lower green-sand and the Portland stone ; 7. Calcareous strata, con- 

 taining the fossils of the Portland stone, and of the same mineralo- 

 gical character with the beds of that formation in the Isle of Pur- 

 beck ; 8. Clay, like that of Kimmeridge, &c. 



The succession in the vicinity of Aylesbury is nearly the same 

 with that of the Vale of Wardour ; the Portland stone being covered 

 at Whitchurch by beds of whiteish fissile limestone, containing 

 freshwater shells, among which are Cyclades, and a species of Cypris. 

 The Portland strata occur also at Brill Hill in Buckinghamshire, and 

 at Garsington in Oxfordshire ; and the remarkable nodules of Shot- 

 over-hill, though differing considerably in appearance from the lime- 

 stone of Portland itself, must probably be referred either to that 

 formation, or to a group of strata which, from their abounding in 

 green particles, might be confounded with some of the calcareous 

 beds of the lower green-sand, but which, both in Buckinghamshire 

 and on the coast of the Lower Boulonnois, occur beneath the equi- 

 valent of the Portland stone. 



At the close of this meeting, which terminated the session, the 

 Society adjourned till Friday evening, the 2nd of November. 



