286 Prof. A. Leymerie on the Lcmer Greensand. 



the waters of the seas would have invaded the country of the 

 Wealds, carrying with it the germs of the Neocomian species, 

 which are now found among those of the greensand, and the 

 greatest part of which we have already mentioned in our me- 

 moir. We shall remark, in conclusion, that these species are 

 found associated, in the lower strata recently discovered in 

 England, with fossils which are only found in France in the 

 bed for which we have reserved the name of greensand. Be- 

 sides the Exogyra sinuata, we could cite the Ammonites Des- 

 hayesif Pecten interstriatus, Plicatida pectinoides, Terebrattda 

 sella, T. elegans, and others which we have never met with in 

 the Neocomian strata. 



After the reading of this paper, M. A. d'Orbigny announced 

 that Dr. Fitton had brought him some fossils from the Isle of 

 Wight, and that on seeing them he had not the least doubt left 

 that that formation was the Meocomian formation : there are 

 from fifteen to twenty well-characterized Neocomian species, 

 which admit of no uncertainty. There is not the least sepa- 

 ration, in England, between the end of the gault or Aptian 

 formation and the Neocomian formation. 



M. de Roys said that he had shown to the geologists of 

 Vaucluse Dr. Filton's list of fossils; they recognised all these 

 fossils as belonging to the upper portion. 



M. A. d'Orbigny cited the Perna Midleti among these fos- 

 sils as a species of the lower part of the Neocomian formation. 

 It is certain, however, that the greatest number of the species 

 belong to the upper part. In other respects he concurred in 

 the views of M. Leymerie respecting the determinations of 

 the fossils of Dr. Fitton. 



M. Leymerie stated that there was one difference between 

 his ideas and those of M. A. d'Orbigny. The strata contain- 

 ing Exogyra sinuata are in perfect accordance with the gault 

 and the greensand. If some Neocomian fossils are found in 

 the greensand of England, there is nothing surprising in that. 

 Formations have taken place in estuaries, whilst, on the land, 

 the Neocomian system was forming. The Perna Midleti alone 

 strikes him as being found in the greensand, above the Weald 

 clay. It is a species which survived in England. 



M. A. d'Orbigny replied that there is in England the same 

 series of species as in France, of the best characterized Neo- 

 comian formation, and at the same level ; that there is no dif- 

 ference in the superposition of the strata in the two countries. 

 If Dr. Fitton has changed the names, it matters not ; but M. 

 A. d'Orbigny had seen the fossils, and Dr. Fitton himself re- 

 cognised at Wassy the same species. 



