A. J. Julies-Broivne 8f W. Hill—GauU and Chalk Marl. 73 



in Norfolk. The gronnds on which these gentlemen venture to 

 doubt its existence are these : — 



(1) No clear line of sepai'ation between the Gault and Chalk 

 Marl, and no phosphatic bed marking the base of the latter, 

 could be found by the Geological Surve3^ors. 



(2) They give a list of unphosphatized fossils from the marly clay 

 of West Dereham, which they regard as a Chalk Marl fauna. 



(3) The phosphatic casts of Gault species they regard as derived 

 fossils. 



From these premises, and without any attempt to determine the 

 horizon of the Totternhoe Stone, which would fix the upper limit of 

 the Chalk Marl, the}^ come to the conclusion that the whole of the 

 so-called Gault in Norfolk is Chalk Marl, and not really Gault. 



We have recently endeavoured to follow the subdivisions of the 

 Chalk through the western parts of Suffolk and Norfolk, and having 

 visited the localities mentioned by Messrs. Reid and Sharman, we 

 wish to record our entire dissent from their conclusions, and to give 

 our reasons for maintaining the existence of Gault in West Norfolk. 



(1) In the first place we found that the upper part of the Chalk 

 Marl changes its character as it is traced northwards, and becomes 

 a hard greyish chalk, passing, in fact, into the " hard chalk," which 

 Messrs. Eeid and Sharman speak of as resting upon " the Chalk 

 Marl." At Stoke Ferry, twenty-two feet of this' hard " Chalk Marl " 

 is exposed below the representative of the Totternhoe Stone ; its 

 full thickness is probably about thirty feet, and between it and the 

 level of the springs on the border of the [Gault] clay plain, there 

 may be ten or fifteen i'eet of soft Chalk Marl. Now the width of the 

 clay plain near West Dereham is about two miles, and an easterly 

 dip of only 1° would give a thickness of fifty-nine feet. That this 

 calculation is within the mark is proved by a boring at Wretton, 

 west of Stoke Ferry, the particulars of whicla were obtained by Mr. 

 Whitaker, and which gives a thickness of sixty feet of clay at a spot 

 which is certainly below the summit of the clay. If, therefore, the 

 whole of this clay is to be referred to the Chalk Marl, we must add 

 it to the thickness of the overlying beds above mentioned in order 

 to get the total thickness of this stage ; doing this we obtain a 

 minimum of 100 feet, and a possible thickness of 120 feet for the 

 Chalk Marl of Norfolk. Near Cambridge its thickness is about sixty 

 feet, and we are therefore asked to believe that it has expanded 

 to double its thickness in a direction in which all the beds are 

 evidently and admittedly thinning out. 



(2) In the next place we cannot allow that the assemblage of 

 unphosphatized fossils obtained from the clay is such as to merit the 

 name of a " Chalk Marl fauna." Nearly all of them are species 

 which range from the Gault to the top of the Lower Chalk, and 

 are therefore of no use in deciding the exact age of the bed containing 

 them. The only species on which any argument can be founded are 

 Belemnifes atfenuatiis, B. minimus, and Ostrea acidirostris. 



The Belemnites are decidedly Gault forms, and do not, so far as 

 we know, occur in true Chalk Marl, where Belemnites are not 



