380 Correspondence — R. M. Brydone. 



coE.E.E;s:po3sri:>E2srcE!. 



THE DIVISION OF THE UPPEE CHALK. 



Sib, — Mr. Jukes-Browne's article under this heading in the April 

 number divides itself naturally into two parts, one dealing with the 

 personal aspect, the other (not altogether impersonally) with the 

 scientific aspect. 



As for the personal aspect, the position is as follows: Certain 

 observations as to faunal changes within the old zone of A. qiiadratus 

 were judged at the time of the publication of "The Zones of the 

 Chalk in Hants " not to amount to evidence of zonal breaks ; they 

 were therefore treated as indicating the existence of subzonal breaks, 

 whose exact position and nature were then not yet ascertained. 

 A large body of further observations enabled me to define the exact 

 position and nature of these breaks and showed that one of them 

 was of zonal importance, involving the proposal of a new zone. 

 Mr. Jukes-Browne announced this intended proposal of mine in such 

 a form that the natural inference was that it was a mere reshuffling 

 of the , data already published — the last thing I desired, and 

 forced upon me by some one else's unauthorized version of my 

 unpublished work. 



As for the scientific aspect, some of the points originally raised (or 

 which could be raised on his reply) are not of sufficient general 

 interest to justify further elaboration. Of the broader points, what 

 was expressly stated to be a fact concerning the Yorkshire clifi's is 

 now admitted to be an assumption ; and the tabulation of records from 

 the old zone of A. qtiadratus in Sussex under the new zone of 

 0. pilula, a representation of fact, is now admitted to be based on an 

 assumption which happens to be false, there being at least 100 feet 

 of the restricted zone of A. qtiadrahis exposed in the Sussex cliffs. 

 Surely it is not very " captious" to object to these assumptions being 

 presented as established facts. Mr. Jukes-Browne was not told by 

 me that he "had no right" to make the assumption as to Yorkshire. 

 He is entitled to make any assumption ; his grounds for making it 

 are then a legitimate subject of criticism. 



Several broad points seem to go by default, e.g. that the highest 

 Yorkshire chalk is so far jS^orth-Gerraan in its apparent affinities that 

 its nomenclature should be North-German rather than Anglo-Parisian, 

 and its fossils should not be mixed up with those of the Anglo-Parisian 

 chalk of Sussex ; or again, that records from Yorkshire, where no 

 chalk of the restricted zone of ^. quadratus is admitted to be preserved, 

 cannot logically be used to prove the absence of certain species in that 

 epoch. If this were logical it could be proved tliat in Kent all the 

 common fossils of the Chalk died out in the zone of Marsupifes. 



Mr. Jukes - Browne now writes of a "Yorkshire zone of 

 A. ffranulatus'\ a zone quite novel to me. It would be interesting 

 to know where to find a definition of this zone and how it is 

 distinguished from the zone of 0. pilula or Scaphites hitiodosus, or 

 again, from Dr. Howe's " local zone of Inoceramus lingua". 



Mr. Jukes-Browne's challenge to me to prove that A. grmiulatus 

 does occur in the restricted zone of ^. quadratus is really irrelevant. 



