184-6.] PRESTWICH ON THE ISLE OF WIGHT TERTIARIES. 247 



stinct and characteristic. The great bulk of the specimens are named 

 by English naturalists, and few foreign species are given by their 

 foreign synonyms, those which are so being precisely the ones, such 

 as Limncea longiscata^ Planorbis rotundatus, P. lens, &c., which at 

 the period of publication were supposed to be peculiar to the fresh- 

 water formations of the Paris basin. 



But in reality we have in the seventy-eight species quoted above, 

 (taking also their synonyms) twenty-three French species. 



Limnsea pyramidalis, Brard and Sow. (L. cornea, Brongn.) 



longiscata, Brongn. and Sow. 



Planorbis lens, Brongn. and Sow. 



rotundatus, Brongn. and Sow. 



Melanopsis ancillarioides, Desk. (M. buccinoidea, Fer.) 



Corbula nitida, Sow. and Desk. 



Nucula deltoidea. Lam. 



Cerithium funatum, Sow. (Cerithium variabile, Desk.) 



Potamides cinctus. Sow. (C. cinctum, Desk.) 



acutus, Sow. (C. acutum, Desk.) 



plicatus, Sow. (C. plicatum ? Lam.) 



ventricosus, Sow. (C. ventricosura. Desk.) 



Ancillaria subulata, Sow. (Ancilla subulata. Lam.) 



Globulus depressus, Sow. (Natica depressa, Desk.) 



Infandibulum trochiforme, Lam. and Sow. (Calyptraea trochiforrais, Desk.) 



Melania margin ata. Lam. 



Voluta spinosa, Lam. 



Ostrea crepidula. Desk. 



flabellula, Lam. 



Psammobia solida, Sow. (P. rudis, Lam.) 



Lucina divaricata, Lam. 



Natica glaucinoides, Desk. 

 Note. It is doubtful whether the Venus incrassataoi Sowerby is synonymous with 

 the Cytherea incrassata of Deshayes, a well-known fossil of the lower part of the 

 *Gres de Fontainebleau.' M.Nyst of Brussels in his recent work * says distinctly 

 that they are not the same species, but that the English species agrees rather with 

 a Belgian one from the sandy calcareous beds of the middle Eocene period. 



In addition to these foreign species found in the Isle of Wight, 

 eight English species, viz. Paludina lenta, Cyrena cuneiformis, 

 C. deperdita, Mya (Potamomyd) plana, Tellina ambigua, Denta- 

 lium entale, Pleurotoma colon and Cancellaria evulsa, occur also in 

 France. 



Let us now examine the distribution of these thirty-one species 

 in the French strata. Of the whole number I believe that only 

 Planorbis lens and probably also Limncea cornea are limited in 

 their range to the ' Calcaires lacustres.' The Planorbis rotundatus 

 has been found in some of the divisions of the ' Argile plastique ' ; 

 and, according to M. d'Archiac, it occurs associated with Limncea 

 longiscata in the upper beds of the calcaire grossierf, but charac- 

 terizes more especially the overlying freshwater deposits. The 

 Cyrena cuneiformis and Melanopsis buccinoidea are characteristic 

 of the 'Argile plastique' of the department of the Aisnef and the 



* Description des Coquilles et Polypicrs Fossiles des Terrains Tcrtiaires de la 

 Belgique, p. 181. 



t Mem. de la See. Geol. de France, vol. v. p. 23G ; also the Mem. of Con^taiit 

 Prevost. 



X Mem. de la Soc. Geol. de France, vol. v. p. 303. 



