342 Mr. Parkinson on the Strata^ 



to be shells strictly belonging to the subjacent stratum, but which, 

 having lain uppermost, became involved in the first or lowest de- 

 position of the blue clay. 



Immediately beneath the clay there is found a line of about three or 

 four inches of the preceding shells imbedded in a mass of calcareous 

 matter, the result of their disintegration. Beneath this are nume- 

 rous alternating layers of shells, marl, and pebble?, for about twelve 

 or fifteen feet. The shells are those which have been already men- 

 tioned ; but are very rarely to be met with whole, and when entire 

 are so brittle as to be extricated with much difficulty. In some of 

 these layers scarcely any thing but the mere fragments of shells are tq 

 be found, and in others a calcareous powder only is left. 



The pebbles are almost all of a roundish oval form, many of them 

 being striped, but differing from those of the superior gravel stratum, 

 in being seldom broken, in there being few large ramose masses, and 

 in their not bearing any marks or traces of organization. Many of 

 these pebbles are passing into a state of decomposition, whence they 

 have in some degree the appearance of having been subjected to the 

 action of fire : small fragments of shells are every where dispersed 

 amongst them. 



Beneath the pebbles is a stratum of light fawn-coloured sand of 

 about ten feet in depth, and immediately under this is the stratum 

 of white sand, which is about five and thirty feet deep, and is here 

 seen resting immediately on the chalk. 



At Plumstead, about a mile distant in a south-eastern direction, there 

 is a pit, in which the shells, about two years ago, were to be obtained 

 in a much better state of preservation than at New Charlton ; but this 

 seam of shells, as the pit has been dug further in, has by degrees 

 become so narrow as to be now nearly lost. In this pit,^npt only 

 the shells already mentioned were found, but many tolerably per- 



