1898] ALBIAN AND CENOMANIAN IN FRANCE 201 



I only know of two cases where A. varians and A. rostratus are 

 said to be associated: one is in the highest bed of the Greensand in 

 North Dorset where both are rare. The other is the record by Mr 

 Price of A. varians from his bed XI. at Folkestone, but the varians 

 was a doubtful specimen and no other has since been found. Mr 

 Munier-Chalmas states that A. varians occurs with A. rostratus in 

 the East of France, and doubtless it does occur occasionally at the 

 summit of the A. rostratus zone. Such occurrences are not rare 

 near the junction of two stages, and they only prove that there is 

 no hard and fast line separating one fauna from another. It is 

 generally conceded that in the delimitation of zones or stages, we 

 must be guided by the abundance of certain characteristic species 

 not by the mere occurrence of one or two of them. Consequently 

 those who arque that the zone of A. rostratus must be C^nomanien 

 because A. rarians sometimes occurs near the. top of it are re- 

 versing the rule, and seek to establish a precedent which would 

 destroy our principles of classification. 



Mr Dollfus has said " it is an illusion to think that we can ever 

 possess a perfect classification which would satisfy geologists of all 

 countries." That is quite true, but it is not an illusion to believe 

 that we can frame a classification which will suffice for one strati- 

 graphical province or basin of deposition, such as that of England 

 or Xorthern France. 



I do not seek to upset the French nomenclature, on the con- 

 trary I recognise that the French will accept no other nomenclature. 

 Endeavours have been made to employ it in England, but at present 

 that is impossible. D'Orbigny's names have been so wrested from their 

 original application by the modern French geologists that many English 

 geologists think that these names no longer possess any fixity of mean- 

 ing ; consequently they oppose the adoption of them. There are of 

 course some who see that the alterations are merely personal views 

 of grouping, and that the faunistic differences on which the names 

 were founded remain the same. So far as the divisions of the Chalk 

 are concerned, we may eventually be able to employ the French names, 

 and the time will be hastened if our French confreres will restrict the 

 Cenomanian to its proper limits ; but with respect to the English Gault 

 and Greensand I see no alternative but to propose a new name. 



I hope at any rate to have made it clear that I do not advocate 

 " a return to antiquated classifications based mainly on mineralogical 

 fades." On the contrary I believe that Mr Dollfus and I are in 

 perfect accord in regard to the principles of classification. We 

 both consider palaeontology and stratigraphy to be the true guides, 

 and we only differ because we interpret the teaching of these guides 

 in different ways. A. J. Jukes-Browne. 



Etecria, Tobquay. 



