104 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



ficiently distinct for M. D'Archiac to give a separate list of those of 

 the department of the xlisne*. They there amount to 96. 



In France this division appears to indicate a shallowing or silting- 

 up of the sea-bed, the occasional prevalence of fresh and brackish 

 water, and the proximity of dry land, whereas in the English area 

 no evidence of a like condition exists. On the contrary, the pre- 

 ceding conditions of sea-bed seem but little changed, and conse- 

 quently, whilst we had in France a terrestrial, freshwater, and sestua- 

 rine fauna, in England a purely marine fauna still obtained. Therefore 

 the French fauna, as a whole, is peculiar to France, and is not repre- 

 sented in this country ; but still the synchronism of the division is 

 indicated through the circumstance, that there are intercalated marine 

 beds in the French division containing shells which form part of the 

 English marine fauna of that period. 



4 . The fourth or uppermost division is not often of much import- 

 ance. It is but little developed in the Marne, but swells out and 

 becomes well marked in the Aisne, where, according to M. D'Archiac, 

 it attains a thickness of nearly 60 feet. In the Oise this group does 

 not exceed 25 feet in thickness : as it ranges westward in this depart- 

 ment it decreases to 1 2 and 3 feet, and appears to thin out altogether, 

 or nearly so, before we reach the limits of the Tertiary area. Near 

 Paris this division is known as the " caillasses." In the Aisne, where 

 these beds are most largely developed, they usually contain very few 

 or no fossils ; in appearance they closely resemble some of the compact 

 white and light-green marls of the freshwater series of Montmartre. 

 In some places the Cyclostoma miitnia is the only shell that can be 

 distinguished. At other places M, D'Archiac found it associated 

 with two or three species of Cerithinm, whilst nearer to Paris these 

 two shells occur associated with numbers of Paludina, Limncea, and 

 Planorbis. M. C. D'Orbigny also, in describing these beds in the 

 neighbourhood of Paris, mentions the occurrence of Cyclostoma^ 

 Cyclas, Limncea, and Paludina, together with Corhula^ Venus, and 

 Cerit}imm-\ . As this bed ranges eastward, it becomes thinner, and 

 the character of its organic remains is modified, for M. Graves does 

 not notice the occurrence of land-shells, and mentions only one fresh- 

 water shell, the Paludina nana, whereas he gives a list of nine brack- 

 ish-water species almost all common to the underlying beds. Of these 

 only one species, the Crassatella r^ostrata, occurs at Bracklesham. 



The upper two divisions of the Calcaire grossier may possibly 

 correspond with the upper 130 to 200 feet of the Bracklesham and 

 White Cliff Bay beds. {c. and part of h. ?) 



It thus appears that the upper Calcaire grossier is in the eastern 

 part of the French basin almost entirely freshwater ; that these 

 conditions are less marked in the central area, are much modified in 

 the eastern, and do not exist at all in England, where marine forms 

 continue up to the very top of the Bracklesham series. Of the ten 

 fossils which M. Graves quotes from these beds, two are species which 

 are not found in the other divisions of the Calcaire grossier, but 



^- Mem. Soc. Geol. de France, vol. v. p. 236. 

 t Tab. syn. But few species are named. 



