402 [May 1, 



tliose named by M. Montmollin belong to our green-sand, M. 

 Leymerie, tliougli lie i-egards the aspect of the Neufchatel series as 

 quite distinct from that of the Aube, considers the two deposits as 

 perfectly identified by their fossils. The limestone below the 

 " Marie bleic " of Neufchatel either does not appear in England, or 

 is represented by the two lowest beds at Atherfield, so remark- 

 ably abundant in fossils. If this be the case, our fullers' eai'th at 

 Atherfield and Hythe may represent the blue maii (30 feet in 

 thickness), and our Kentish limestone (129 feet), at Hythe, may 

 be the equivalent of the upper " yellow limestones," from 120 to 

 160 feet thick. 



§. A very important extension of the tract occupied by the Neuf- 

 chatel deposit has since been made known by M. Jules Itier, in a 

 memoir read before the Institute of France * ; from the report on 

 which it appears that the Neocomian strata in the department of 

 the Aisne have a maximum thickness of 300 metres ; which, the re- 

 porter adds, is far inferior to that of the same formation in the 

 department of the Isere, and of the South of France. Among the 

 fossils of this department, the most remarkable and characteristic 

 is the Chama ammonia {Caprotina of D'Orbigny), from whence, 

 or rather from its synonyme Diceras, the term " calcaire a dice- 

 rates " has been applied to some lower members of the chalk series, 

 in what has been called the " bassin mediterraneen." 



§. To any one familiar with the chalk distxicts of England, and 

 those of France near the coast of the English Channel, it would 

 be surprising if the series of beds below the chalk on the east of 

 Paris were very different from that of the west. M. Leymerie's 

 map of the department of the Aube appears to indicate the same 

 series as that of England ; yet it is difficult to identify his sub- 

 divisions at the upper part of the series with ours. His general 

 divisions of the subcretacean groups are, Argile-teguline and gres 

 vert, about 150 metres (about 490 feet) ; and Terrain neocomien, 

 50 metres (164 feet) ; the latter including three subdivisions, which 

 seem to be the equivalents of part of our green-sands, — viz. a. 

 Argiles et sables bigarrees, containing much iron ore ; b. Argiles 

 ostreennes, (about 25 metres) ; c. Calcaire a spatangus, about 13 

 metres (about 42 feet). 



§. In confirmation of the evidence which proves the superposition 

 of our English equivalent of the Neocomian to the Wealden 

 group, it may be remarked, that the fishes of the latter deposit are 

 considered by M. Agassiz as more intimately allied with the oolitic 

 than with the cretaceous series ; and a similar observation has been 

 made by Professor Owen with regard to the Wealden reptiles. 

 If, therefore, a marine equivalent of our Wealden should be dis- 

 covered, analogy would lead us to expect in its fossils a character 

 approaching to that of the Oolites, from which M. D'Orbigny re- 

 gards the whole of the cretaceous species as perfectly distinct: — and 

 for such a deposit the best name would probably be that of " Ma- 



* Comptes rendus, &c. de I'Acad. 22 Aout, 1842. 



