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.” ! 
Careful and repeated examination of the fine coast section near 
Havre led us to dissent entirely from Professor Hébert’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,” 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 ‘Cénomanien.’ 
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. 
Referring 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 confréres 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. lii., p. 99 (1896). 
2 Fewille des Jewnes Naturalistes for February 1898, No. 328. 
