CHAP. XII.] ICENIAN PERIOD. 23? 



the imperfect nature of the fossils then found, and the 

 apparent presence of some Eocene species, led others to. 

 regard them as Lower Eocene. In 1886, however, Mr. 

 Clement Eeid was able to settle the question by obtaining 

 fresh specimens, which proved the beds to be of older Plio-. 

 cene age. The sands often contain flint pebbles, and include 

 layers of loamy clay and seams of fossiliferous ironstone, 

 and though their aspect is not that of deep-water deposits, 

 yet the perfect and unworn condition of the shells shows 

 that they are not shore deposits, and the fauna seems to. 

 indicate a depth of at least 20 fathoms. 



The Lenham Sands occur at intervals along the Downs 

 from the heights above Folkestone to Chipstead, near 

 Croydon, 1 but though they are now found along this narrow 

 tract, it is evident that they are the remnants of a forma-L 

 tion which was once far to the north, and also some distance 

 to the south of this line. It would appear, in fact, that 

 though the upheaval of the Wealden area commenced in 

 Eocene times, and though this district was exposed ta 

 erosion throughout the times of the Tipper Eocene, Oligo-. 

 cene, and Miocene, yet that the great plane of denudation 

 out of which the present surface of the Weald is carved waa 

 formed by the waters of the early Pliocene sea. Conse-. 

 quently, if we would restore the surface over which the 

 Lenham Sands were laid down, we must imagine a sea- 

 floor stretching northward from the summit of the Chalk 

 escarpment at a high level above the Isle of Sheppey and 

 the estuary of the Thames. Fig. 6 is an attempt to restore 

 this horizon, and, allowing for some subsequent elevation 

 over the Wealden area, to show the position which the base 

 of the Lenham Sands would now occupy if they had not 

 been so largely removed by subsequent erosion. Over 



1 At present, however, fossils haA'e only been found at Lenham, and 

 it is open to doubt whether the Chipstead sands, and those of Headley- 

 still further west, are precisely of the same age. 



