of the Red Limestone of Hunstanton, 239 



or a subordinate member of the Chalk. The Red Limestone 

 everywhere conformably underlies the white Chalk, and uncon- 

 formably overlies the Speeton Clay, the upper part of which 

 would appear to be newer than the Lower Greensand. At Spee- 

 ton there is said to be a gradual change from the red chalk to 

 the white ; and at Hunstanton, but for the colour, it would be 

 scarcely possible to separate the chalk from the red bed below, 

 since they are linked together by the ramose sponge, which, 

 commencing in the red stratum, grows on into the grey beds 

 above. From this latter circumstance it is impossible to ima- 

 gine any vast epoch between the deposition of the red beds and 

 the white ; the fact would rather indicate a sequence of deposi- 

 tion. The chalk above is clearly Lower Chalk. The red bed is 

 as clearly, by the evidence of two-thirds of its fossils, not Lower 

 Chalk. If, then, it is below the Lower Chalk, and to some ex- 

 tent linked to it by a succession of characteristic animal growth, 

 the presumption would appear very strong that the deposit 

 should be a member of the formation immediately below in the 

 stratigraphical succession, i. e. of the Upper Greensand. Like 

 the Gault, the Greensand may be said to fall in with the strike 

 of the Limestone, with the thickness of which, in the Eastern 

 counties, it corresponds. And should the fossils sanction it, there 

 would, on a Greensand hypothesis, be much less difficulty in 

 accounting for the presence of Chalk and Gault fossils than by 

 any other supposition ; for where, in a deposit near to the Chalk 

 age, there are the conditions of Chalk strata, there probably will 

 be found some Chalk species. Of the Gault shells it would be 

 impossible to say how many are derived from denudation of that 

 formation, and how many may have lived on and migrated from the 

 Gault sea; but the fact that the larger proportion of the fossils of 

 the Cambridge Greensand was previously only known from the 

 Gault should warn us against laying much stress on their presence, 

 or endeavouring to account for them by other than the most 

 natural causes. And, supposing the deposit to be Greensand, it 

 would not appear absolutely necessary that it should correspond 

 with our English types ; for there are some indications of a tract 

 of land having separated the seas between Cambridge and Lynn 

 during the Cretaceous era ; and if such existed, there might be 

 aijy amount of divergence in the respective faunse of deposits of 

 the same age. It does not closely approach any Continental 

 deposit, though the Tourtia and our English Farringdon gravel 

 present palseontological conditions essentially similar. 



The following analytical Table of the fossils of the red bed 

 will show its affinities with, and differences from, the other 

 Upper Cretaceous rocks : — 



