16 



The author furtlier observed, that above the before-mentioned 

 unfossiliferoiis lose bed at Pegwell Bay, and. g( nerally, in thi- synclinal 

 depressions in the chalk from thence to Canterbury, a dark tenaeious 

 clay bed was met with for the most part fossiliferous, containing 

 Dentalium sp. Is'atica subdepressa, Modiola sp., Pholadomya cuneata, 

 and Koninckii, Thracia oblata, Nncula Bowcibankii and Cyprina 

 'Moirissii, often only as casts ; it was further noted that the more sandy 

 beds of the Thanct series overlaid these clay beds and constituted a bigger 

 zone, in which occurred tabular concretions of sand-stone, and occasionally, 

 silieified shells or casts. 



The beds resting upon these Thanct series, it was noted, although 

 classed as belonging to the Woolwich beds, presented no marked character 

 in lithological or paloeontological features, but, nevertheless, may be 

 recognised by the careful observer, by the characters indicated in the 

 Geological Survey Memoirs. 



The Author was rather iurlined to the view of Mr. Gardner, who, 

 instead of a three-fold classification of the beds in East Kent between the 

 chalk and London clay, made but two, (separating the Thanet beds from 

 the Old Haven beds, and classing the Woolwich series in East Kent 

 with the Thanet below.) and to follow the latter gentleman in 

 classifying the lower eocenes in respect to their marine cstuarine and 

 fresh water characters. 



Attention was drawn to Mr. Harris' paper in the proceedings of the 

 Geologist's Association, in some respects coinciding with Mr. Gardner's 

 views, but classing the Old Haven with the Beading and Woolwich 

 series, thns making, in fact, only two divisions instead of three, 

 including the whole of the beds between the London clay and Thanet 

 beds as one series. 



The older Geologists, it was remarked, classed all the beds from the 

 chalk to the London clay as one, under the term Plastic Clay series. 

 It would seem to be rather a retrograde motion in these days of 

 subdivision to adopt these comprehensive views ; for practical purposes 

 it is better to follow the leading of the writers of the Geological Survey 

 Memoirs. The present notice of the lowest of these beds resting upon 

 the chalk, led the author to adopt one additional division under the terra 

 of Basement Bed of the Thanet, which, he believed, had as good a title 

 to a separate division, as those advocated by Mr. Whitaker. But, he 

 considered, the most difficult part of geological science, was the 

 correlation of beds of marine and fresh water character, where there had 

 been oscillations of level accompanied by alternate marine and fluviatilc 

 conditions. 



The Bibliography of the subject is added, which may be useful to 

 the student. 



Bihliograpluj. 



1817. — Buckland. — Doscriptiou of some specimens from the riastic Clay, near 

 Reading, Berks. Geological, Trans., series 1, vol. iv, p. 277. 



