166 A. J. Jukes-Browne — Division of Upper Chalk. 



"With respect to Sussex I relied on the published records, according 

 to which 0. pilula is common at intervals throughout the 170 feet 

 exposed in tlie cliffs between Seaford and Brighton, while A. granidatus 

 occurs through at least the lower 150 feet, where no true A.grcomlattis 

 had been found. Moreover, when Mr. Brydone wrote to me in 

 October, 1911, he said that he liad found there was in Hampshire 

 a marked break in the middle of the ancient zone of A. quadratus, 

 and that " so far as is known A. quadratus does not range below it 

 in Hants or Sussex". Since then, however, he appears to have 

 obtained fresh evidence, and has found in Sussex specimens which he 

 '^expects to prove that there also A. quadratics ranged down into the 

 upper division of the zone of 0. pilula^'. 



When I compiled my tables I had no reason to suppose that the 

 restricted zone of A. quadratus came into the Sussex cliffs, and 

 consequently I entered both Inoceramus pinniformis and /. tuherculatus 

 as referable to the zone of 0. pilula. When Mr. Brydone has published 

 his fresh investigation of the Sussex coast-section, and has described 

 the exact position of his restricted zone of A. quadratus in it, the 

 precise location of these Inocerami will be of importance. The greater 

 part of this higher zone must certainly be above all the Brighton 

 chalk, and can only be found in the more western part of Sussex. 



While I resent criticism that seems to be of a captious nature 

 I assure Mr. Brydone and other readers that I welcome any fresh 

 information and any definite corrections of the records in the tables 

 which I compiled. The delimitation of the two zones in question has 

 not yet been accomplished through the South of England nor in the 

 North of France, and consequently my tables are a first attempt to 

 show the change of fauna that seems to occur at about this liorizon. 

 Without essaying such a tabulation it would have been impossible to 

 compare the zonal distribution in England with that which has so far 

 been recorded in France and Germany. 



With regard to Belgium Mr. Brydone makes a statement which is 

 inaccurate. He says T have tabulated A. verus, A. quadratus, and 

 B. mucronata as having "absolutely distinct ranges in Belgium", 

 and thinks it " dangerous to tabulate the ranges of A. verus 

 and B. viucronata as separated by two whole zones". I have not 

 done so, and if he will look again at Table II he will see that 

 both A. quadratus and B. mucronata are entered in the fifth column 

 (zone of A. quadrattis). I did not include A. verus because 

 de Grossouvre in 1902 had expressed a doubt of its actual occurrence 

 in the Craie de Trivieres, which represents the zone of A. quadratus. 

 Possibly I should have accepted M. liutot's record in spite of 

 de Grossouvre's doubt, but Mr. Brydone knows that A. verus is very 

 rarely found above the Marsupitcs zone, and in his recently published 

 Stratigraphy of the CJtnlk of Hants he records one from the 

 quadratus zone of Hampshire, remarking that "it is believed to 

 be unique at that horizon for England ". On the other hand, 

 I wonder if the B. mucronata recorded from Tiivieres can really be 

 B. lanceolata, a form or species which does not seem to have been 

 recognized in Belgium or France, but which is known to occur in the 

 qtiadratus zone in England. 



