218 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 25, 



Marne * ; and in the same formation the Potamomya plana, Tellina 

 ambigua, Paludina lenta and Melanopsis ancillarioides occur occa- 

 sionally ; they rarely or never extend higher in the series. 



"J'he Melania marginata, Natica depressa and N. glaucinoides 

 range from the ' Lits coquilliers ' to the upper calcaire grossierf. 

 The Corbula nitida, Psammobia rudis and Valuta spinosa are well- 

 known calcaire grossier species, but occasionally the latter two range 

 rather higher ; the Cancellaria evulsa, Pleurotoma colon and Ceri- 

 thium ventricosum 2ixe met with, in the 'Lits coquilliers'; and the 

 Nucula deltoidea, Ancilla subulata, Calyptrma trochiformis, Lucina 

 divaricata and Ostrea flabellula are found in all the beds from the 

 lower sands to the upper marine and freshwater deposits, and the 

 Cyrena deperdita in the ' Gres moyens.' 



The relations of the several species of the genus Potamides of 

 Sowerby to those of the Cerithium of the French authors are rather 

 ill-defined, and, from the great number of unnamed species, the sub- 

 ject requires further investigation. The Cerithium cinctum and C. 

 plicatum are rather characteristic of the upper marine and freshwater 

 deposits ; whilst C. acutum and C. concavum are common in the 

 upper ' Calcaire grossier,' C. acutum and C. ventricosum in the ' Lits 

 coquilliers,' and C. variabile in the lignites of the ' ArgileplastiqueJ.' 



In addition to these recognised species, I have found in the cal- 

 caire grossier of Damery a species of Natica and a Fusus, not distin- 

 guishable from specimens from Headon Hill. 



Thus the representative forms of the period of the * Sables infe 

 rieurs' are more abundant even than those of the formations above 

 the ' Calcaire grossier,' and as a group the forms of this latter de- 

 posit evidently predominate. 



Referring again to the first list with regard to their geological 

 range in this country, we find the following thirteen in the London 

 clay of Barton, Alum Bay, or Bracklesham Bay : — 



Dentalium entale. Sanguinolaria compressa. 



Ancillaria subulaia. Lucina divaricata. 



Cancellaria evulsa. Infundibulum (Calyptreea) trochifortne. 



Mitra pumila. Globulus (Natica) depressus. 



Pleurotoma colon, Modiola elegans. 



Voluta spinosa. Buccinum desertum. 



Ostrea flabellula. 



Again, the Melanopsis fusiformis, Paludina lenta, Cyrena obovata, 

 C, cuneiformis and C. deperdita are well-known and common fossils 

 at New Cross and Woolwich in the beds under the London clay, and 

 the Cerithium funatum at Newhaven ; and Mr. Sowerby quotes the 

 Fusus labiatus as occurring at Woolwich or Flumstead, Potamomya 

 plana at Flumstead, and Neritina concava at Charlton. 



It thus appears that nearly all the species which are known else- 

 where show relations with the earlier Eocene strata. 



Of the new species (nearly forty in number) at present confined 



* Annales de I'Acad. de Rheims, Mem. of Rondot.p. 15. 

 t Mem. de la Soc. Geol. de France, vol. v. pp. 236, 261 and 272. 

 X Deshayes (Coq. Foss.) quotes the Melania inquinata and Helix dubius from the 

 Isle of Wight, and M. d'Archiac (Bull. Soc. Geol. vol. x. p. 212) the Ostrea crepidula. 



