1869.] coquand cretaceous strata. 247 



Discussion. 



Mr. J. W. Flower called attention to the great discrepancy be- 

 tween the thickness of the Cretaceous beds of the south of France 

 and those of England, the former being four times the magnitude of 

 the latter. This was principally made up by several strata entirely 

 wanting in England, and for the most part of a totally different 

 character, being either of freshwater origin or else hippurite lime- 

 stone. Another great feature of distinction was the presence of 

 coal-bearing beds with numerous layers of lignites. That these 

 beds were of Cretaceous origin was proved by their occurrence under 

 undoubted Eocene beds. Among the fossils of the Algerian chalk 

 were those of several genera unknown in the Cretaceous beds of 

 England. 



Dr. Duncan suggested that possibly the Upper Coal-beds might be 

 the equivalents of those of Aix-la-Chapelle. He doubted whether 

 any decided synchronism in strata spread over so extensive an area 

 as that of the Cretaceous deposits could be established by the mere 

 occurrence of certain fossils in them; nor could he attach much 

 value to supposed specific differences in shells of such character as 

 Ostrea. The variations in condition in the sea-bottom would lead 

 to variations in the Testacea ; and there were signs to be found of 

 great variations going on before the form of Hippurites was deve- 

 loped. He regarded Hippurites as a modified form of Chama or 

 Caprina, and thought it was parasitic on coral, reefs in the same 

 way as its modern representative. He accounted for its presence by 

 the great development of corals at that period in the Cretaceous seas. 



Mr. JuDD remarked upon the repeated changes which had oc- 

 curred in the opinions of foreign geologists as to the limits of the 

 various '^ stages" into which the Cretaceous rocks might be divided, 

 and indicated that this of itself was equivalent to the abandonment 

 of the principles laid down by D'Orbigny. He further observed 

 that in the recent changes, even as evidenced by M. Coquand's 

 paper, there was a tendency to approach the views as to the classi- 

 fication of the Cretaceous beds established by the late Prof. Edward 

 Forbes, and generally accepted by English geologists. 



Prof. Morris observed that the object of the French geologists 

 had been to remove the opinion that mere mineralogical charac- 

 ters were sufficient to distinguish Cretaceous strata. He called 

 attention to the existence of copper and antimony in some of the 

 Lower Cretaceous beds, and to the great break that appeared to 

 exist between the Lower and Middle Cretaceous series. Another 

 curious point was that in the south of France there appeared 

 to be passage-beds between the Upper Cretaceous and Eocene beds. 



Prof. T. EuPERT Jones remarked on the analogy between the 

 passage from the Chalk to the Eocene Tertiaries, as supposed to be 

 exhibited in the south of France and in the Nebraska territory of 

 America. He pointed out that as the Cretaceous beds of France 

 had been deposited, not in one sea, but in separate sea areas, they 

 were, of course, diflicult of correlation. 



