1866.] WHITAKEK LOWER LONDOIT TERTIAEIES. 409 



clay " above the base-bed in sinking a well at Stourmouth, nearly 

 the whole of which must beiong to cl*. 



This marl is more sandy towards the top^ and passes up into 

 the next division. 



(e) The uppermost part of the Thanet Beds consists of a fine sharp 

 light-grey sand, of a slightly greenish tinge, often ironshot, and here 

 and there with layers of calcareous sandstone, as at the Eeculvers 

 and Pegwell Bay. 



It contains fossils, which near Faversham are sometimes silicified, 

 as Mr. Prestwich has observed, though with some doubt whether 

 the bed which contained them belonged to this or to the overlying 

 series f. Mr. Dowker has a large and well-preserved silicified core 

 from a pit in this sand at Canterbury ; it is hke that figured by 

 Lindley and Hutton J, which must have come from this formation 

 or from the Woolwich Beds, though described (by some mistake) as 

 from " green sand " near Deal. Mr. John Goodchild, of Sitting- 

 bourne, has lately found some Crustacean remains and distorted 

 Cyprince and Plioladomyce in the brickyards close to that town ; 

 these, however, must have come, I think, from low down in the 

 sand, where it passes into the marl below. 



From a thickness of 30 or 40 feet near Canterbury, this decreases 

 westward and thins out before we reach Rochester. 



§ 3. Wo?)LWicH AND Eeading Beds. 



(1) The ** bottom bed " does not occur in the most eastern part 

 of the Kentish Tertiary district ; and consequently it is there very 

 difficult to divide the sands of this series from those of the under- 

 lying Thanet Beds. 



At the mouth of the tunnel on the 'Whitstable Eailway at Can- 

 terbury, the lowermost part of the Woolwich sand is rather clayey 

 and green, contains a few pebbles, and is more regularly bedded 

 than the higher parts ; and this is all that I have seen to represent 

 the bottom bed in the neighbourhood. At Sittingbourne, however, 

 there is a foot or more of pebbly green sand, and at TJpnor rather less 

 of the same. Wes;:wardthis thickens, and from Erith to London 

 the bed consists of from 3 or 4 to 15 or more feet of a rather b -ight- 

 green sand, with flint-pebbles, both in la> ers and scattered. 



West of London, where the Reading Beds rest on the Chalk, the 

 structure changes, ardinstecd of the pebbly light-green sand, with 

 no fossils but the teeth of Lamnm and sometirres an Ostre%, there 

 are grey laminated clays, with green grains and here ard there 

 casts of shells §, and dark clayey greensand, with unworn green- 

 coated flints. 



(2) Near Canterbury the Woolwich Beds consist almost wholly 



^ The Geologist, vol. iv. p. 213 (1861). 



t Quart. Journ, Geol. Soc. vol. viii. p. 246, and vol. x. p. 109. 



t The Fossil Flora of Great Britain, vol. ii, pi. 125. 



§ Geol. Survey Mem. on Sheet 13, p. 24. 



2 F 2 



