196 NATURAL SCIENCE [September 



1895, and the results were published in a joint paper with myself 

 on the " Delimitation of the Cenomanian in England and France." 1 

 Careful and repeated examination of the fine coast section near 

 Havre led us to dissent entirely from Professor Hubert's grouping and 

 to agree with those French geologists who had placed the base of the 

 Cenomanian above the local representative of the Gaize (or zone 

 of Ammonites inflatus). We showed, in fact, that the series near 

 Havre is obviously and naturally divisible into an Albian and a 

 Cenomanian, which exactly correspond with the two English stages 

 of (1) Gault-cum-Greensand, and (2) Lower Chalk. 



Our descriptions and arguments did not however carry convic- 

 tion to the mind of Mr G. Dollfus, who discussed the question in 

 February last, 2 and maintained that our views were not in accord- 

 ance with the palaeontological evidence. The July and August 

 numbers of the same periodical contain a rejoinder to this attack, 

 in which the friendly challenge was taken up and the palaeontolo- 

 gical argument stated more fully than had previously been attempted 

 either in England or France, with the advantage of being translated 

 into French by my courteous opponent himself. 



As the French nomenclature has been adopted in most European 

 countries, it becomes a matter of international importance to decide 

 what is to be connoted by the terms ' Albien ' and ' Cenomanien.' 

 I desire, therefore, to publish part of my reply to Mr Dollfus in its 

 English version, and this (with a few small corrections) constitutes 

 the remainder of the present article. 



Eeferring to the section at Wissant Mr Dollfus remarks : " If 

 Mr Jukes-Browne wishes us to place the line of separation above the 

 clay with Ammonites inflatus, far from making us take a step forward, 

 he would lead us backward ; his opinion is that of a period which we 

 out-grew in France twenty-five years ago." That depends on the 

 point of view ; I think that twenty-five years ago the geologists of 

 France took a path which deviated from the right road ; it is quite 

 true that I seek to lead them back from this wrong path, and I pro- 

 pose that we should walk together along the straight highway of 

 progress. That is my hope, but I know that I have first of all to 

 essay the difficult task of persuading my confreres that the path 

 they took was a wrong one. 



In the first place let us consider the Cenomanian of the typical 

 area near Le Mans. How was this stage established ? D'Orbigny 

 did not go into stratigraphical details, but he studied the fossils which 

 had been found in the beds near Le Mans, and he saw that the fauna 

 as a whole was different from that of the Albian of Dienville and the 

 Gault of Wissant. D'Orbigny, it is true, thought that there was only 



1 Quart. Journ. Geol. Soc, vol. Hi., p. 99 (1896). 



2 FeuUle des James Nalvralistcs for February 1898, No. 328. 



