Vol. 54.] 



LENHAM BEDS AND COKALLINE CKAG. 



317 



was accumulated previously to the deposition of the Coralline Crag, 

 or cliffs of older Pliocene sandstones may have continued to exist 

 along the south-western margin of the Crag sea during a part of 

 the Eed Crag period. 



If the conclusions to which the facts here enumerated seem to point 

 be correct, the Lenham Beds may be considerably older than the 

 Coralline Crag, these two deposits being separated from each other 

 by an interval sufficiently long to allow for the consolidation and 

 subsequent denudation of the former,^ as well as for the disappear- 

 ance from the Anglo- Belgian basin of a number of species of 

 mollusca which abounded in it during the Miocene, and continued 

 to do so until the earlier part of the Pliocene period. 



Although the Lenham Beds are connected stratigraphically with 

 the sands of Louvain and Diest, the molluscan faunas of the two 

 deposits, while presenting some resemblance, are, as to individual 

 species, by no means identical. The difference may be due to the 

 fact that the collection of fossils from either is small, and therefore 

 imperfect ; or the Diestien Sands may represent a considerable 

 period, and the fossiliferous beds which they contain may be of a 

 somewhat later age than the Lenham deposit. Fossil shells are 

 not common in these sands, and when they do occur it is in the 

 form of casts, which is also the case at Lenham. 



The species known from the Diestien Sands (zone a Terehratula 

 grandis) are the following : — 



List of Mollusca peom the Diestien Sands of Belgium. 





Lenham 

 or Box- 

 stones. 



Miocene 



or Ital. 



Pliocene. 



Cor. 

 Crag. 



Extinct. 



Voluta Lamherti, Sow 



* 



if 



If 



* 



* 



* 

 * 



•5f 

 •K- 



•«■ 

 ■jf 



* 



it 



? 



? 

 * 



Nassa lahiosa, Sow 



„ reticosa, Sow 



,, var. elongata, S. V. W 



Pyrula reticulata, Linn 



Cassis Sahuron, Brug 



Buccinopsis Dalci, Sow 



Murex scalariformis^ Nvst 



Trophon co7isocialis, S. V. W 



Fusus QTacilis, Da Costa 



Pleurotoma C7'assa, A. Bell 



Conus Dujardinii, Desh 



Pleurotoma inermis, Part 



„ intorta, Broc 1 



„ var. plicatilis, Nyst ... J 

 Aporrhais pes-pelicani, Linn 



Turritella incrassata, Sow 



Natica millepunctata, Lam 



„ varians, Dui 





1 Prestwich believed that the Lenham Beds had been upheaved prior to the 

 deposition of the Coralline Crag, Quart. Journ. G-eol. Soc. vol. xxvii (1871) 

 p. 134. See also A. Bell, Geol. Mag. 1872, p. 209. 



