54 Geological Society. 



Six species of corals, and remains of Lumna and Myliobates.have been 

 also ascertained to occur at Bossee ; and a posterior molar tooth 

 which Mr. Lyell procured there, Mr. Owen has proved to belong to 

 the Dichobunes, a genus of Pachyderms, found likewise in the Eocene 

 strata of France and the Isle of Wight. 



Pontlevoy. — At this town, thirty miles south-east of Tours, a patch 

 of white Falun marl rests on the Eocene freshwater formation. In 

 the pits east of the town Mr. Lyell procured perfectly preserved 

 shells ; and fragments of the Eocene freshwater limestone are found 

 in the Falun bored by Petricolje, and full of their shells. The marl 

 is usually covered by three feet of red clay, sand and mould. Mr. 

 Lyell found here the first specimens of the shell, generally con- 

 sidered to be the Valuta Lamberti of the English crag, but which he 

 believes to differ from it. During his researches at Pontlevoy he 

 procured 163 species of shells, forty-five of which, or twenty-five per 

 cent., have been identified with existing Testacea ; and on comparing 

 the whole number with a collection of 180 from Louans, 106 were 

 found to be common to the two localities. Only thirty-four of the 

 Pontlevoy shells were not procured by Mr. Lyell, at some other Fa- 

 lun locality. Not more thcin six species of corals have yet been as- 

 certained to occur in this district. The other localities near Pont- 

 levoy examined by Mr. Lyell are Sambin and Contres. At the 

 former the white Falun, containing hard flags, is covered by a great 

 deposit of red, ferruginous, stratified gravel, with grains of quartz and 

 flint derived from the Eocene freshwater formation ; and it bears a 

 striking resemblance to the gravel-beds which overlie the red crag 

 in Suffolk. Immediately east of Sambin, as well as between Contres 

 and Soing, Mr. Lyell found specimens of the Ostrea virginica asso- 

 ciated with fragments of other Testacea, which identified the deposits 

 from which they were obtained with those of Touraine. These de- 

 tached Faluns imply, he says, that a large part of France, now 

 drained by the Loire and its tributaries, was submerged during the 

 Miocene period, although it is only at a few isolated points that the 

 evidence can be detected of the long time this submergence must 

 have lasted, and of the distinctness of the fauna which then lived, 

 both from that now existing, and still more from that of the ante- 

 cedent Eocene epoch. 



General Remarks. — Previously to his tour, Mr. Lyell considered 

 that the collections which he had seen from the Loire might be di- 

 vided into two groups, the larger resembling a Mediterranean or even 

 a more northern fauna, and the smaller a tropical one ; and that some 

 of the shells composing the latter came from inferior beds of the de- 

 posit, or from patches of Falun of more ancient date than others : 

 he also suspected, that where the tropical forms abounded, there 

 would be found a smaller proportion of recent shells. He is, how- 

 ever, now convinced that all the shells belong to one group, or that 

 the forty-four crag species were really contemporaneous in Touraine 

 with the large cones, Cyprseas, Fasciolarias, and other tropical forms 

 of Testacea. At Bossee, where he found these large univalves, as well 

 as the Astrsea, Lunulites, and Dendrophyllia, most fully developed, he 



