254 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr. 21, 



out of the Thanet Sands westward of London, and the rise of the 

 " Ostrea Bellovacina" bed of Reading from the surface of the Chalk 

 to the zone of the Woolwich fluviatile series at London, are points 

 which are not clearly exhibited in open sections, but which are better 

 made out by the sections afforded by the wells to the westward of 

 London. 



Although the Thanet Sands are limited in their range westward to 

 about the parallel of Windsor, yet with regard to their range eastward 

 it is probable that they attain a more important development in the 

 north of France and Belgium than in England. I have seen them in 

 the neighbourhood of Calais, where they underlie the London clay, 

 and from the description of M. Galeotti* and Omalius D'Halloyf , it is 

 probable that the beds overlying the chalk at Tournay belong to this 

 same age. The Pholadomya, PanopcEay Astarte, and Cucullcea are 

 there found in beds of nearly the same mineral characters, but their as- 

 sociates are species which do not occur in England. There is, however, 

 apparently some error in the lists of these shells. When the results 

 of M. Dumont's admirable researches are better known, the compari- 

 son of these lower tertiaries will be readily made. He has already 

 published a sketch of the co-relations of the Belgian with the French 

 and English tertiaries J, but as it is unaccompanied by sections and 

 without lists of organic remains, I cannot judge of its accuracy. In 

 his visit to this country last summer, he pointed out to me the many 

 characters common to these Thanet sands and to his "Landenian 

 System," which occupies the same position in the Belgian series §. 



The recent visit of Sir Charles Lyell to Belgium will, I have no 

 doubt, remove the uncertainty which we feel respecting the organic 

 remains, and throw light on the relations of the English with the 

 Belgian tertiaries, — a point of much interest, as these two series are 

 evidently much more closely related than the English are with the 

 French series. 



The lower tertiary beds in France have been described by M. Elie 



as I have never myself found any traces of shells in this bed in the numerous sec- 

 tions of it I have examined throughout Kent, nor can I hear of their having been 

 observed by others. It is, however, quite possible that the Ostrea Bellovacina, or 

 some other large species of oyster, may occur in the Thanet sands, as several 

 species of shells are common to this and the overlying group. I have, in fact, re- 

 cently found a fragment of a large oyster in the lower part of these sands, near 

 Faversham, but it is evidently not the 0. Bellovacina. 



* Mem. de I'Acad. de Bruxelles, vol. xii. 1837, and also his separate work on 

 the geology of Brabant. 



f Coup d'oeil sur la Geologic de la Belgique, 1842. 



% Rapport sur les travaux de la Carte Geol. de la Belgique, 1839, in the Bull, de 

 I'Acad. Roy. de Bruxelles, vol. vi. p. 11. Ibid. vol. xvi. 1849. " Sur la position 

 geologique de I'Argile RupeHenne, et sur le synchronisme des Formations ter- 

 tiaires de la Belgique, de I'Angleterre, et du Nord de la France," Ibid. vol. xviii. 

 No. 8, 1851. 



§ Since writing this paper I have visited the " Systeme Landenien," in the 

 neighbourhood of Mons and Tournay, and perfectly agree with M. Dumont in 

 considering it synchronous with the " Thanet sands." His determination of the 

 order of superposition of the Belgian tertiaries seems as skilful as, there is every 

 reason to believe, it is accurate. I had not, however, an opportunity of examining 

 any but the lower divisions of the Tertiary series. — May 1852. 



