574 MESSES. JUKES-BBOWNE AND W. HILL ON THE LOWEK PAKT 



guides in this case, unless it can be sJiown that they have been derived 

 from an older stratum. Mr. Whitaker suggests the possibility of 

 their derivation, but frankly admits that he knows of no evidence 

 in favour of it ; neither do we, for the Gault species of the Eed 

 Rock seem to be in just the same state of preservation as the 

 others. 



The following statements were made by one of us when supplying 

 Mr. Whitaker with a list of the fossils in the Red Rock of Hun- 

 stanton, and are quoted by him in the paper referred to : — " Palseon- 

 tologically the Hunstanton Limestone has stronger affinities with 

 the Gault than with any other formation,". ..." its affinities with 

 the Chalk-marl are less strong : it must be remarked that none of 

 the specially characteristic Chalk-marl species are found." Our 

 recent researches have only strengthened the data on which these 

 two statements were founded. 



On reference to the list (Table I.), it will be seen that nearly all 

 the fossils we have found in the Gault of Norfolk occur also in the 

 Eed Rock. Further, if we confine our attention to the Cephalopoda, 

 which are usually regarded as the best guides in correlating strata 

 of Secondary age, we find that no fewer than eight Ammonites, of 

 characteristic Gault species, have been recorded from the Red Rock. 

 These are : — Ammonites auritus, Am. JBeudanti, Am. interrivptus, 

 Am. lautus, Am. ochetonotus * , Am. rostratus, Am. sjplendens, and 

 Am. tuber culatus. Ammonites varians, Am. Coujpei, Am. Mantelli, 

 Am. navicularis, and Am. falcatus, which are the characteristic 

 Ammonites of the Chloritic Marl and the Chalk-marl, are con- 

 spicuously absent from the Red Rock. 



The extreme rarity of Gasteropods in the Red Rock, while they 

 are abundant in the Gault of Southern England, finds a natural 

 explanation in the hypothesis that we are dealing with a deep-water 

 fauna ; for they are always rare in deep-water deposits, and at the 

 present day their numbers always diminish with depth of water and 

 distance from land, Pleurotomaria being the only genus that is now 

 indicative of deep water. 



* Recently found in the Lower Gault of Bucks, as have also all the other 

 species, including Am. rostratus, which has hitherto been supposed to occur only 

 in the Upper Gault. 



