The Upper Gault in England and tlte "Red Chalk ". 195 



adventitious coloration of the uppermost red bed and the presence 

 in it of mumte polished black grains, there is close lithological 

 resemblance between these two strata. Both have the same nodular 

 asjDect, and are characterized by the same peculiar ramifying con- 

 cretionary structures (absent in the two beds below) and by the 

 presence of numerous Inocemmi. One of these shells seen by us in 

 the uppermost red bed belongs, we consider, to Inoceramus crippsi 

 Mantell, which also occurs in the " Sponge Bed ". We saw also 

 in both these beds Inoceramus tenuis Mantell and a small Terehratula, 

 distinct from those occurring so commonly in the lower red beds, 

 as well as a bryozoou (common) and Spondi/lus latus (J. Sov/.), 

 neither of which was fouud lower down. It must not be forgotten 

 that S. Wood\v'ardi reported the rare occurrence of "Ammonites 

 varians " in the Red Chalk, a record Avhich unfortunately cannot 

 now be tested, since the v/herea bouts of the specimen or specimens 

 is unknoAvn. 



The occurrence of Chalk fossils in the topmost red bed probably 

 gave rise to the view held b}'' Gunn ^ and by Mr. W. Whitaker that 

 the Red Chalk should be regarded as the basal part of the true 

 Chalk series. The claim made by Gunn that the latest fossil types, 

 not the earlier ones, must be used in identifying the age of a deposit, 

 sound in itself, was nullified in this case by his regarding the whole of 

 the red strata r.s of one age. Had he known that the fauna of the 

 uppennost red bed has a different character from that of the two 

 lower beds, he would probably have realized that the base of the 

 Chalk series includes only the uppermost foot of the Red Rock. 



We have been able to detect no sign of a break between the base 

 of the Red Rock at Hunstanton and the overlying unstained 

 Chalk ; and we feel bound to regard this as an exceedingly condensed 

 series laid down under conditions of slow accumulation, representing 

 a facies of sedimentation for the most part different from that 

 exemplified in the corresponding rocks farther south. Pro- 

 fessor Barrois stated that the zone of Pecien asper is absent in 

 Norfolk. The familiar development of this zone elsewhere, always 

 as a glauconitic sandy deposit carrymg a special faunal facies 

 depending on sub-littoral conditions, precludes its recognition in an 

 area where the facies is so strongly contrasted. Its attenuated 

 equivalent may well be there. Similarly, the lowest bed of the 

 varians-zone of Wiltshire and Dorset, with the fauna that includes 

 Catopygus columharius Lam., Terebrirostra lyra (J. Sow.), and other 

 characteristic species, iii all probability has very condensed repre- 

 sentation in some part of the uppermost red bed at Hunstanton. 



The well-known lenticles of fossiliferous limestone found at Harris's 

 sand-pit at Shenley Hill, near Leighton Buzzard, have been correlated 

 by us with the basal bed of the varians-zone. Some of the gritty 



^ S. Woodward, An Outline of the Geologjj of Norfolk, p. 54, Norwich, 1833. 

 ^ J. Gunn, "Notes on the Red Chalk of Hunstanton": Proc. Norwich 

 Geol. Soc., pt. i. Session 1877-8, p. 23, Norwich, 1878. 



