newton: conchological features of lenham sandstones. ii3 

 Conclusions. 



We gather from the previous hterature on this subject that the 

 majority of investigators have agreed that the Lenham Beds are 

 equivalent to the Diestian deposits of Belgium, which have been 

 generally recognised by geologists as belonging to the base of the 

 Pliocene system, on account of the shell remains exhibiting a marked 

 Miocene facies with many species identical or related to southern or 

 Mediterranean forms. The Miocene aspect of the Lenham fauna is 

 very pronounced, as out of the seventy-seven conchological species 

 that have been determined in the present work, forty-seven, or sixty 

 per cent, date their origin from the Vindobonian (Helvetian- 

 Tortonian) stage, which represents the middle part of that epoch in 

 such countries as Germany, Italy, France (S.), Holland, Denmark, 

 and Austria (Vienna Basin). Again, twenty-six of the Lenham species 

 occur as well in the Redonian beds of Gourbesville, Normandy, which 

 are either of Vindobonian or Messinian age and therefore Miocene. 

 These Gourbesville deposits are of peculiar interest. They were 

 originally discovered by Vasseur,^ and ascribed to Pliocene or Red 

 Crag times, having been more critically studied since by M. G. F. 

 Dollfus,2 who in 1880 regarded them as of similar age, although sub- 

 sequently determining them as belonging to his^ " Etage, Redonien," 

 which in explanation was stated to be neither Helvetian nor Plais- 

 ancian, but equivalent in time to the Tortonian stage of the Miocene, 

 notwithstanding that he had previously paralleled this new horizon 

 with the Anversian Beds of Belgium.* The Redonian fauna was con- 

 sidered to be related to the Gedgravian (Coralline Crag) of England. 

 About twenty of the Lenham shells, including Anadara diluvii, 

 occur in the Upper and Middle Miocene of Holland, and a rather 

 smaller number of species in the same horizons of Denmark, as deter- 

 mined by Molengraafif and Van Waterschoot Van der Gracht^ for 

 Holland and by Ravn« for Denmark. The Pelecypod, Anadara 

 diluvii, is of frequent occurrence in the Lenham Beds, and although 

 unknown in the Diestian of Belgium, it is found in the Bolderian 

 (=Tortonian) and Anversian (=Messinian) of that country, as well 

 as in the Vindobonian of Germany, France, Austria, and Italy, and 

 m the Plaisancian deposits of Italy and France; its only British 

 occurrence from the Lenham sandstones was first recorded by Mr. 



1 Bull. Soc. Geol. France, 1879, ser. 3, vol. 7, p. 741. 



2 Bull. Soc. G60I. Normandie, 1880. 



3 Assoc. Frangaise-Cherbourg, 1905, published igo6, pp. 358-370. 



4 Bull. Soc. G^ol. France, 1903, ser. 4, vol. 3, p. 258. 



5 Niederlande : Handb. Region. Geologic, 1913, vol. i, part 3, p. 53. 



6 Molluskfaunaen I Jyllands Tertiaeraflejringer, etc., Mus. Mhi. Geol. Universit. Coien- 

 haguc : Paleontologiques, No. 7, 1907 (plates and text), 



H 



