PRESTWICH — WOOLVvICH AND READING SERIES. 115 



sands. With regard to their state of preservation, the Paludina 

 hmestcftie exhibits well-preserved specimens. In the beds beneath 

 this there are considerable bands formed almost entirely of commi- 

 nuted fragments of shells, whilst in some associated beds the shells 

 are preserved entire, but they are generally very friable. In the 

 clays, although not unfrequently crushed, they are sometimes in an 

 excellent state of preservation. In both these parts of the series 

 the several species of Cyrence are often found with their two valves 

 together. This fact was especially observable in the pebbly calca- 

 reous rocks of Deptford*, where scarcely a single valve either of the 

 Cyrena or Modiola is found separate. 



A very interesting example of this description, and of tranquil en- 

 tombment, has been pointed out by Mr. De la Condamine at Wool- 

 wich, where, in one part of the pebbly sands overlying the bed of 

 clay, the Cyrena tellinella, in an excellent state of preservation and 

 the two valves united, occurs in its normal vertical position, as when 

 living it bored into the sands. 



The perfect condition of the Ostrea Bellovacina at Woolwich and 

 Sundridge has often been noticed^. 



In the neighbourhood of Bromley, Chiselhurst, and Lewisham 

 there are beds or bands abounding almost exclusively with this 

 oyster, frequently with the two valves united, and in the position in 

 which it lived. The lowest bed of pebbly green sand immediately 

 overlying the "Thanet Sands" is in this area also characterized by 

 the Ostrea Bellovacina ; not that it is so generally abundant as in 

 some of the upper beds of this group, but it there constitutes, as in 

 the western area, almost the sole fossil. It has been found in this 

 position in sinking several wells in London (Barclay and Perkins's, 

 Truman and Hanbury's, the Bank, the Mint, and others). It is 

 nevertheless scarcely ever met with in this stratum at its outcrop in 

 Kent ; at Erith it occurs occasionally in this bed and of a large size ; 

 and I think it exists also at Oakwells near Boughton. North of 

 London this old eocene Oyster-bed is largely developed at Northaw, 

 where it lies, as it does also at Hertford, immediately upon the chalk 

 without the intervention of the Thanet Sands. On the south ot 

 London it is again found overlying the chalk at Headley-on-the-hill 

 and Fetcham. These fossil oysters frequently exhibit a much-worn and 



Condamine at Woolwich. The upper part of the Woolwich series at Lee and 

 Blackheath has likewise furnished him with several rare species of Neritina and a 

 Bracheux Buccinum. These latter, together with some new species of Cerithium 

 and a Murex of the neighbourhood of Laon, exist also in the fine collection from 

 the Woolwich pits made by Mr. Lunn. It was not until the recent close and 

 careful investigation of Mr. Rosser, that Cytheres were known to occur in such 

 abundance in the pebbly sands of Woolwich, together with well-preserved fish- 

 scales, numerous small indeterminable bones, the eggs and opercula of Molluscs, 

 a variety of small Bryozoa, and Foraminifera. These were chiefly found in the 

 interior of the larger shells. 



* In the railway cutting. 



t Dr. Buckland, in particular, alludes to this circumstance, and to the frequent 

 agglutination of several of these oysters together on some of the large fiiut 

 pebbles. 



i2 



