1898] ALBIAN AND CENOMANIAN IN FRANCE 195 
de l’Argonne contains so many Cenomanian species, (2) that this 
zone overlaps the Lower Gault, and thus in his opinion separates 
itself from the latter. Later in 1876 Barrois expressly included 
the Upper Gault of Folkestone and Wissant in the Cenomanian. 
But he made no estimate of the number of species which united the 
zone of Ammonites inflatus at these places to the beds above, nor 
did either of them ever discuss the relative values of the different 
elements of the fauna of the A. inflatus zone. 
The variation and discordance of opinion in France may be 
gathered from the change in the grouping of the zones in different 
editions of A. de Lapparent’s well-known “ Traité de Géologie.” In 
his edition of 1885 the zone of A. inflatus is grouped as Albian, in 
that of 1892 it is placed in the Cenomanian. The latter method 
of grouping has been adopted by Mr G. Dollfus for the Service 
de la Carte géologique de la France. At present, therefore, most 
French geologists make a very small Albian and a very: thick 
Cenomanian, while the line of separation between the two stages 
is drawn through the middle of the Gault of Wissant and through 
a perfectly continuous bed of sandy clay at Havre. 
In England we have arrived at very different results; De Rance 
in 1868 and Price in 1874 showed that the Gault of Folkestone 
was separable into two divisions—a Lower Gault characterised by 
Ammonites interruptus and A. lautus, and an Upper Gault charac- 
terised by A. varicosus and A. rostratus. In 1876 Barrois published 
his excellent Researches on the Upper Cretaceous Series of England, 
and proved to us that the greater part of our Upper Greensand was 
the stratigraphical equivalent of the Upper Gault of Folkestone. 
Subsequent investigations have led us to regard the combined 
Gault and Greensand as a single stage or natural group of beds, to 
_ abandon the names Gault and Greensand as denoting definite chrono- 
logical divisions ; they can only be regarded as descriptive of different 
lithological aspects or facies of the formation, and consequently as 
serviceable only on maps that are designed to exhibit such lithological 
variations. Hence we can recognise with Barrois a zone of Ammon- 
ites rostratus (= inflatus), but it is quite impossible for us to accept a 
classification which groups this zone with the Lower Chalk and separ- 
ates it from the Lower Gault. | We base our refusal on the very 
principle by which the French themselves profess to be guided, namely, 
on the faunistic relations of the several zones, and especially on the 
range and relative abundance of the different species of Cephalopoda. 
Now a classification which appears to be the best and most 
natural expression of the facts in southern England can hardly be 
unnatural in the north of France, and thus it became clear that 
some study of the French sections from an English point of view 
was greatly needed. Such a study was made by Mr W., Hill in 
