110 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 13, 



developed ; whilst land shells are scarcer and are m greater part 

 such as frequent marshy places and damp woods. 



With the Grays fauna, these two deposits present only a few 

 species in common ; but a difference of conditions, such as a 

 greater body and depth of water, combined with a probable occa- 

 sional slight brackishness, may account for this variation; for although 

 many of the species are distinct at these three localities, yet they all 

 agree in the common fact of the species being identical with recent 

 species, and such as for the most part still remain associated in like 

 position, under like conditions, in this country at the present day. 

 All the three deposits belong, I believe, to a period subsequent to 

 that of the Boulder Clay ; but the arguments on this subject I must 

 reserve to a future occasion, when I have gone into the evidence 

 afforded by the various drift-beds of the valley of the Thames and of 

 the adjacent counties more in detail. 



One of the principal points of interest attaching to this particular 

 section is the clear indication of two gravel-periods separated by an 

 interval of dry-land surface, — a character common throughout this 

 district, and to which also we shall have occasion to allude in greater 

 detail on another occasion. 



The following are the Mollusks I have found in this deposit. For the 

 determination of the species I am indebted to Mr. J. Pickering: — 



Shells from the clay beneath the gravely Shacklewell Lane. 



Bithinia tentaculata {Linn) ; and Carychiura minimum, Miill. 



its opercula. Zua lubrica, Mull. 



Valvata piscinalis, Miill. Pupa muscorum, Linn. 



Limnaeus palustris. Linn. Helix pulchella, Miill. 



truncatulus, Miill. aculeata, Midi. 



glaber ?, Miill. hispida ?, Linn. 



stagnalis ?, Linn. Zonites radiatulus, Alder. 



Succinea putris, Linn. nitidus, Miill. 



Planorbis marginatus, Drap. crystallinus, Miill. 



spirorbis, Linn. Pisidium pulchellura, Jenyns. 



nautileus, Linn. obtusale, Jenyns. 



Clausilia, sp. ? pusillum, Turt. 



The shells of this deposit are in a very rotten and often frag- 

 mentary state, and it is probable that there are many more species. 



3. On a FossiLiFEROus Bed of the Drift Period near the Re- 

 culvers. By Joseph Prestw^ich, Jun., Esq., F.R.S., F.G.S. 



This deposit is, like the one described p. 101, spread over the base 

 of a hill, which here slopes down to the marshes separating this part 

 of Kent from the Isle of Thanet. It is exposed in two pits near 

 Wear Farm (see Ordnance Map), on the road from Chislet to the 

 Reculvers. The height of the ground above the level of the adjacent 

 marsh or of the sea, does not exceed 20 to 30 feet. The pit in a 

 field to the east of the road offers the best section ; it is as follows : — 



