212 



1 foot, Vegetable earth. 



2 feet, Brown loamy earth, containing spines and plates of echini. 



11 Strong blue clay, with no animal remains, except a few of 



echini. 



If Bed of large white lime-stone nodules, in the upper part, 



containing anomiae striatue, cockscomb oysters, auricu- 

 larke plotii (gryphites), and small ammonites. 



12 Blue clay, of an unctuous feel, which terminates on the 



bed of stone. 



Mr. Platt says, " In this clay, about four feet above the stone, lie the 

 broad flat oyster, with some belemnites and vertebrae of fishes. I was 

 present at the falling of more than a hundred tons of this clay, by under- 

 mining it at the surface of the stone ; and was much entertained by see- 

 ing the pretty appearance which the broad oysters made in their num- 

 ber and different sizes, all lying horizontally : some as broad as my two 

 hands, others small as a shilling." 



O. deltoidea, of Lamarck, possesses those characteristics which mark 

 the Shotover Hill oyster flat, like a placuna; a deltoidal form; car- 

 tilaginal pit shallow, oblique, conical, and transversely striated ; and trans- 

 verse irregular striae on the edges of the valves, on each side of the pit. 



At Woolwich, in the pyritous clay, among the cyclades and ceri- 

 thia, already mentioned, oysters are frequently found ; but, from the 

 great changes they have sustained, and from their extreme brittleness, 

 I am unable to speak with any -precision as to their specific differences. 

 They however appear to be of two species : one, long and narrow ; 

 about four inches in length, and about an inch in width ; and the other 

 semiglobose, and of about three inches diameter. But all the specimens 

 which I have seen, of this, as well, indeed, of the other species, appear 

 to have lost their external laminae, and with them, of course, an impor- 

 tant distinguishing character, that of their external surface. 



In the adjoining parish of Plumstead, however, and at little more than 



