GO R. M. Br y done — l:itages of the Upper Chalk. 



unfavourable there, as Mr. Jukes-Browne adopts, by reference to " The 

 Zones of tlie Chalk in Hants ", definitions of the boundary in Hants 

 which, while not very precise, might well enable it to be identified 

 in other counties in a clilf or good pit section. At the same time it 

 is liardly likely that any collections from the old zone of J. quadratus 

 made before 1911, when Mr. Griffith and I first published our 

 proposed subdivisions of it, were either made or labelled with such 

 close attention to the particular planes of division that we adopted, or 

 otherwise so accurately labelled as to precise locality, that they can, 

 except in rare cases, be now definitely referred to one of those 

 subdivisions. 



The difficulty is best shown by a concrete case. 



Mr. Jukes-Browne credits the zone of 0. pilula, but not the 

 restricted zone of A. quadratus, with Inoceramus tuherculatiis and 

 /. pinnifonnis on the strength, according to his own showing, 

 of Mr. Woods' citation of both these species from the zone of 

 A. q^iadratus of Brighton and Yorkshire. The 'Brighton' specimen 

 of /. hiberculatus was collected by Dr. Rowe, probably before 1900; 

 the ' Brighton' specimen of /. pinnifonnis before 1871. It is quite 

 possible that since the beginning of 1911 the exact spot at which 

 I. tuherodatus was found has been pointed out by Dr. Rowe or identified 

 from bearin^^s furnished by him, and its position with reference to 

 the divisions made by Mr. Griffith and myself (which are absolutely 

 reproduced on the Sussex coast) worked out, and it is also just possible 

 that the same has been successfully done with the ' Brighton ' 

 specimen oi I. pinniformis ; but it is not stated to have been done, 

 and nothing less would justify the use of these ' Brightim ' specimens 

 in distinguishing the zone of 0. pilula from the restricted zone of 

 A. quadratus. 



Another question which arises in connexion Avith the Yorkshire 

 Chalk is whether, if the whole or part of a zone other than the 

 restricted zone of A. quadratus can be identified as succeeding the 

 zone of Marsupites in Yorkshire, that zone is properly labelled " zone 

 of Offaster pilula ". 



^ow it was long ago pointed out by Barrois that the highest Chalk 

 of Yorkshire showed strong signs of affinity to the German Chalk, 

 and Dr. Rowe has furnished us with plenty of evidence that during 

 several Chalii epochs, one of them being the epoch succeeding the 

 zone of Marsupites.^ there is strong evidence of restriction in the 

 affinity between Yorkshire and South England, owing probably to 

 a higli submarine ridge between them. On the particular evidence 

 that in the Anglo-Parisian basin the zone of Marsnpites is succeeded 

 by a zone which is characterized by 0. pilula and does not 

 contain Scaphites hinodosiis, that in the !North German basin the 

 zone of Marsnpites is succeeded by a zone which is characterized 

 by S. hinodnsHs and does not contain 0. pilula, and tliat in Yorkshire 

 the zone of 2[arsupites is succeeded by a zone which contains 

 S. binodosus in abundance but in which 0. pilula is scarce, it seems 

 highly probable that Yorkshire at that time was essentially an arm 

 of the North German basin and that the Yorkshire zone sliould be 

 termed the zone of S. binodosus, and that in an inquiry as to synchronism 



