286 Geological Society : — 



The chief interest of the paper probably centres in the Gault, and 

 its relations to the Chalk Marl and the lied Chalk. Quite recently 

 the very existence of Gault in Norfolk has been disputed, but the 

 Authors think the facts they adduce and the fossils they have found 

 will decide that point. The Gault at Stoke Ferry is about 60 feet 

 thick, and in the outlier at Muzzle Farm Ammonites interruptus 

 occurs plentifully in the form of clay-casts with the inner whorls 

 phosphatized. At Roydon a boring was made which showed the 

 Gault to be about 20 feet thick, the lower part being a dark blue clay, 

 above which were two bands of limestone enclosing a layer of red marl, 

 and the upper 10 feet were soft grey marl ; the limestones contained 

 Amm. rostratus, Amm. lautus, Inoceramus sidcatus, and Inoc. concen- 

 tricus (?), while the marls above contained Belemnites minimus in 

 abundance. At Dersingham another boring was made which proved 

 the grey marl (2 feet) to overlie hard yellow marl, passing down into 

 red marl, which rests on Carstone. The grey marl thins out north- 

 ward, and as the red marl occupies the position of the Red Chalk, 

 the Authors believe them to be on the same horizon, an inference 

 confirmed by the presence of Gault Ammonites in the Red Chalk. 



Another point of importance is the increasingly calcareous nature 

 of the Gault as it is followed northward through Norfolk. This 

 was regarded as evidence of passing away from the land supplying 

 inorganic matter, and approaching what was then a deeper part of 

 the sea ; this inference is borne out by the microscopical evidence. 



As regards the Chalk Marl, it also becomes more calcareous : at 

 Stoke it is still over 70 feet thick, and its base is a glauconitic marl 

 which can be traced to Shouldham and Marham, but beyond this 

 the base is a hard chalk or limestone, which is conspicuous near 

 Grimston and Roydon, and passes, as the Authors believe, into the 

 so-called " sponge bed " at Hunstanton. 



The Totternhoe Stone is traced through Norfolk, but is thin at 

 Hunstanton (2 feet) ; its existence, however, enables the limits of 

 the Chalk Marl to be defined, with the result that some 13 feet of 

 the hard chalk at Hunstanton must be referred to that subdivision. 



The Grey Chalk also thins northward, and from 90 feet near 

 Cambridge is reduced to about 30 at Hunstanton. The Belemnite- 

 marls are traceable in Norfolk, but either thin out or are replaced 

 by hard white chalk near Heacham. 



The Melbourne Rock is continuous, and maintains similar charac- 

 ters throughout. 



The total diminution in the thickness of Lower Chalk is from 170 

 feet at Newmarket to 55 feet at Hunstanton, viz. 115 feet. An 

 endeavour was made to estimate the amount and extent of Gault 

 removed by erosion from Arlesey and Stoke Ferry. 



5. " On some Occurrences of Piedmontite-schist in Japan." By 

 B. Koto, Esq. 



The occurrence of mangan-epidote or piedmontite in connexion 

 with the glaucophane-bearing rocks, in the crystalline schists of 

 Japan, had already been indicated by the Author. But the onura- 



