IN THE ANGLO-PARIS BASIN in 



ites inflatus being included by him in the Cenomanian. Nonetheless, the terms ' Zone 

 of Ammonites mammilare ' and ' Zone of Ammonites interruptus ' were first used by 

 De Ranee (1868) at Folkestone. Barrois stated that the type area of the interruptus 

 Zone was the Aube but he recognised that in this area there was a mixture of what he 

 thought to be the fauna of the mammillare Zone (e.g. Douvilleiceras of the clemen- 

 tinum group) and that of the interruptus Zone in the clays classified with the latter 

 Zone. In 1878 (265, footnote) it was obvious that Barrois was worried by this 

 admixture for he states that possibly Ammonites lyelli might have been preferable as 

 the index of this zone ; this species being characteristic of the clays of the Gault 

 classified with the interruptus Zone from the Aisne to the Yonne. 



Price & Delatour (1879 ; 38-42) concluded that all the beds of the Lower Gault at 

 Folkestone had their representatives in the Gault of the Aube, but neither of these 

 workers had seen the sections on the opposite side of the Channel. Price and Barrois 

 knew each other, and it is significant that Price also refers to a Zone of Ammonites 

 lyelli and places it above the Zone of Ammonites mammillaris. Barrois, like many 

 of his contemporaries in France, when considering the zonal scheme, was strongly 

 influenced by the very full development of the mammillatum Zone, and the eodentatus 

 and lyelli Subzones in the Gault of the southern part of the Paris Basin. Although 

 Barrois knew the sections at Wissant and Folkestone, and realised that there was a 

 break in the succession below the sediments of the inflatus Zone, he does not appear to 

 have fully grasped the extent of this gap in the observed sequence in the Aube and, 

 therefore, the reason why the sequence in the Aube appeared so different from those 

 on each side of the Channel. The observed gap in the southeastern area of the Paris 

 Basin involves the equivalent of the greater part of the Lower Gault at Wissant and 

 Folkestone, and includes all from the top of the intermedins Subzone to the base of 

 the cristatum Subzone. Whether there is a total absence of deposits of this age in 

 this area is uncertain (p. 97). 



Jukes-Browne (1900 ; 45) adopted the Zone of Ammonites interruptus but 

 restricted it to beds of equivalent age to that of Bed I at Folkestone, the interruptus 

 Zone of De Ranee in part and Price. This reading, excluding the equivalent of the 

 ' Sulphur Band ' brought the English interpretation more into line with the known 

 sequence in the Aube. He realised that the remainder of the Lower Gault at Folke- 

 stone could not be classified with the interruptus Zone, and he proposed that Beds II 

 to VII and their lateral equivalents be included in a Zone of Ammonites lautus. He 

 excluded Bed VIII from both the lautus and rostratus zones (the latter being the 

 equivalent of Barrois ' Zone a Ammonites inflatus) treating it as a junction bed. 



Because Barrois had classified his Zone a Ammonites inflatus with the Cenomanian, 

 Jukes-Browne felt that he could not accept d'Orbigny's name Albien for the stage. 

 He had proposed the name Devisian to encompass the Gault and Upper Greensand of 

 England (1892 ; 266), but this name clashed with the earlier Oxfordian substage 

 name Divesian and the term was replaced by Selbornian (1900 ; 30-31). In reality 

 there was no need for a new name and the terms Devisian and Selbornian are 

 synonyms of d'Orbigny's Albian. Jukes-Browne's zonal scheme and stage name 

 (1900) were employed in England until Spath commenced work on the nomenclature 

 of the Albian (1921). 



