OE THE UPPER CRETACEOUS 1ST WEST SUEEOLK AND NORFOLK. 573 



on the supposition that these beds are Chalk-marl, the occurrence 

 of Inoceramus sulcatus, I. concentricus, Ammonites laittus, and Am, 

 rostratus would be such an anomaly that, if anyone chooses to accept 

 it, he must be prepared to renounce the stratigraphical axiom that 

 " strata can be identified by their fossils." 



We would apply the same reasoning to the Red Chalk of Hun- 

 stanton, where the same Ammonites, together with two others equally 

 characteristic of the Gault, are found, and are associated with Ino- 

 ceramus sulcatus and /. Crij^sii. We do not think that any for- 

 mation containing these fossils in an underived state can be other 

 than of Gault age, whatever the lithological character of the rock 

 may be ; and we feel sure that our friend Mr. Whitaker allowed 

 lithological evidence to have too much weight and pakeontological 

 evidence far too little, when he mapped the Norfolk Gault as Chalk- 

 marl and refused to see anything but chalk in the Red Rock of 

 Hunstanton. 



Mr. Whitaker has discussed the evidence of the fossils in his 

 Address to the Geological Society of Norwich * ; and he asks, " if 

 the rock represent Gault and Gault only, how are we to account for 

 the occurrence of the fossils belonging to higher beds, and some of 

 which have nowhere been found in undoubted Gault '? " This is a 

 very fair question ; but he seems to think that it is much more 

 difficult to account for the appearance of species in any formation 

 which have hitherto only been found in newer and higher beds, 

 than it is to explain the occurrence of species which have only been 

 found in older beds ; we really cannot see why one case should 

 be necessarily more difficult of explanation than the other : every- 

 thing must depend upon the circumstances of the particular 

 case. 



In comparing the succession of faunas at places so far apart as 

 Folkestone and Hunstanton, considerable allowance should be made 

 for the possibility that some species may have come in at one 

 locality before they reached the other ; for it is quite certain that 

 the conditions of life were very different at, the two places— the sea- 

 bottom in the one place was mud, and the water above was not very 

 deep, while in the other place the bottom was a calcareo-ferruginous 

 sediment, and the water was probably much deeper. This being so, it 

 seems to us that the occurrence of a certain number of deep-sea (or 

 Chalk species) is only what might be expected in the Hunstanton 

 deposit. Two of these species, namely Ostrea curvirostris and Tere- 

 bratulina gracilis, have already been found in the marly Gault of 

 West Norfolk ; and we are consequently led to expect that the other 

 precursors of the Chalk-marl fauna of Southern England will be 

 discovered in this deposit. 



We would urge, therefore, in opposition to Mr. Gunn and Mr. 

 Whitaker, that it is by no means the fossils " of the latest type that 

 must be used in identifying the period " of the bed ; but, on the 

 contrary, that it is those of the earliest type that must bs taken as 



* Proc. Norwich Geol. Soc. vol. i. p. 230. 



Q.J.G.S. No. 171. 2q 



