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. 
1^ Bed of large white lime-stone nodules, in the upper part, 
containing anomias striatae, cockscomb oysters, auricu- 
lariae 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, bv 
undermining it at the surface of the stone ; and was much entertained 
by seeing the pretty appearance which the broad oysters made in their 
number 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 ; carti- 
laginal pit shallow, oblique, conical, and transversely striated; andtrans- 
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 cerithia, 
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 im- 
portant distinguishing character, that of their external surface. 
In the adjoining parish of Plumstead, however, and at little more than 
a mile distance, among the same species of cyclades and cerithia, is 
