NEWTON: CONCHOLOGICAL FEATURES OF LENHAM SANDSTONES. I17 



tlieir age as Mio-Pliocene or Messinian, a somewhat similar horizon 

 having already been partially suggested by Gwyn Jeffreys,^ who stated : 

 " He was not clear whether the St. Erth deposit was of Older Plio- 

 cene or possibly of Upper Miocene age." In the same paper Mr. A. 

 Bell placed upon record an important opinion he had received from 

 M. DoUfus, which reads as follows :— " You have in St. Erth exactly 

 the same Pliocene fauna as we have at Gourbesville in the Contentin," 

 a statement more or less confirming the previous researches of Mr. 

 Reid (1890), who had acknowledged the necessity of a strict com- 

 parison between the molluscan species of Gourbesville and those of 

 the St. Erth deposits, as the fossils from the former locality " point 

 to conditions very similar to those indicated by the shells from St. 

 Erth." The Gourbesville fauna, however, as previously mentioned, 

 is now considered to be of Miocene age (Tortonian or Messinian). 

 About fifty per cent, of the Lenham shells are extinct species, a some- 

 what similar per-centage marks the Box-Stone fauna (according to a 

 calculation made from Mr. A. Bell's memoir m/ourn. Ipswich Field 

 Club, 191 1, vol. 3, pp. 7, 8) and Mr. Reid (Survey Memoir, 1900, p. 

 64) has stated that the Coralline Crag and St. Erth deposits contain 

 each about forty per cent, of extinct shells. It will be observed that 

 there is a similarity running through these per-centages of extinct 

 forms, which appears to furnish satisfactory evidence for regarding 

 the four stages of Mr. Reid's " Older Pliocene " group as of the same 

 approximate geological age, although the Box-Stones, as before ex- 

 plained, may be somewhat older. 



From the foregoing details of the different faunas involved in this 

 discussion, it is certain that many of the species had their origin in 

 Miocene times. There is good reason for recognising the St. Erth 

 shells as of Miocene age, because of their relationship to species 

 characterising the French Redonian. Similarly, the Box-Stone fossils 

 would belong to the same period, as their affinities are with those of 

 the Bolderian of Belgium, which is generally regarded as Tortonian 

 or Upper Vindobonian. 



Lastly, the Lenham fauna with its strong Vindobonian and Coral- 

 line Crag facies should also be placed in the Miocene, and in con- 

 sideration of its relationship to that characterising the Upper Miocene 

 deposits of Northern Germany and the Anversian beds of Belgium, 

 I would recognise it as belonging to the latest or Messinian stage of 

 the Miocene, which is synonymous with the term Mio-Pliocene. The 

 stratigraphical name of Mio-Pliocene was introduced into Belgian 

 geology by Mourlon,^ who regarded it as including Lyell's "Upper 



1 Quart. Journ. Geol. Soc, 1885, vol. 41, p. 72. 

 Geologic de la Belgiqiie, 1880, vol. i, p. 261. 



