215 



Carshalton oyster seems to approach much nearer to the form of the fos- 

 sil oysters found near Reading, in Berkshire, being about four inches and 

 a half in length, and about two and a half in width. 



Dr. James Brewer, in the Philosophical Transactions for the year 

 1700, relates the following particulars respecting the bed of oyster- 

 shells found under ground, near Reading, in Berkshire : " The circum- 

 ference where these oister-shells have been digged up and found, con- 

 tains between five and six acres of ground. The foundation of these 

 oister-shells is a hard rocky chalk, and above this chalk the oister-shells 

 lie in a bed of green sand, upon a level, through the whole circumfe- 

 rence, as nigh as can possibly be judged ; this stratum of green sand and 

 oister-shells is (as I measured) nigh two foot deep. Now immediately 

 above this lay re or stratum of green sand and shells, is a bed of a bluish 

 sort of clay, very hard, brittle, and rugged : they call it a pinny clay, 

 and is of no use. This bed or layre of clay, I found to be nigh a yard 

 deep ; and, immediately above it, is a stratum of fuller's earth, which is 

 nigh two foot and a half deep (this earth is often made use of by our 

 clothiers) and above this earth is a bed or layre, of a clear fine white 

 sand, without the least mixture of any earth, clay, &c. which is nigh 

 seven foot deep ; then immediately above this is a stiff red clay (which 

 is the uppermost stratum), of which we make our tiles. The depth of 

 this can't be conveniently taken ; it being so high a hill, on the top of 

 which hath been and is dug a little common earth about two foot deep, 

 and immediately under appears this red clay." The doctor dug out several 

 whole oysters, with both their valves, but found them very brittle. 



I have only to observe on these oysters, that they appear to be a 

 variety of O. edulis ; and that, from their long continuance in a subter- 

 ranean situation, without any lapidifying impregnation, they have become 

 so extremely friable, as to render it very difficult to obtain or preserve a 

 good specimen. 



I have found, among the Essex fossils, besides one very much resem- 

 bling the Bexley oyster, three other species. The one Plate XIV. 



