572 MESSES. JUKES-BROWNE AND W. HILL ON THE LOWER PART 



It will be seen from this list that we succeeded in finding indubit- 

 able Gault fossils at the Muzzle pit, where Messrs. Reid and Sharman 

 could not discover anything to convince themselves that the clay 

 was not Chalk-marl. As already stated (p. 549), the specimens of 

 Ammonites interruptus were mostly in the state of clay casts, a few 

 only having their inner whorls preserved in phosphate, so that no 

 doubt can exist about their being contemporaneous fossils ; and this 

 fact is of itself sufficient to decide the point at issue, even without 

 the other characteristic Gault fossils which accompany them, viz. 

 Nucula pecthiata, Inoceramus sulcatus, and Terebratula Dutempleana. 

 Of the other Inocerami, some seem certainly to be /. concentricus, 

 and others resemble the larger and more compressed species which 

 occurs frequently in the Lower Gault elsewhere, and may be iden- 

 tified with that known as /. Crippsii when found in the Red Chalk 

 of Hunstanton. 



"With respect to the Dereham fossils our list is not so large as 

 that given by Messrs. Reid and Sharman ; but we protest against 

 the elimination of the phosphatic specimens. Similar phosphatized 

 fossils occur everywhere in the lower part of the Gault, often 20 feet 

 above its base, as in Bedfordshire and Buckinghamshire. The state of 

 the Ammonites with phosphatic centres at Muzzle shows why the 

 phosphatic specimens are so often fragmentary ; for if the beds in 

 which such casts lay imbedded were afterwards subjected to the wash- 

 ing of a current, all the fine mud which composed the cast might be 

 washed away and redeposited, leaving only the phosphatic portions 

 in situ. It seems probable therefore that we may regard all such 

 contemporaneous nodule-beds, which are frequent in the Gault, as the 

 sif tings of a certain thickness of clay which contained semiphos- 

 phatized and semiconsolidated casts of fossils. The rounded and 

 broken appearance of the phosphatic fragments does not, then, 

 necessarily show that they have been much rolled or waterworn, for 

 they would present such an appearance as soon as they were detached 

 from that portion of the cast which had not been filled with phos- 

 phatic matter. 



Small oysters, resembling Ostrea acutirostris, Nilss., and 0. cur- 

 virostris, rtilss., certainly occur; but most of those found by us 

 come near to 0. curvirostris, as figured by d'Orbigny, than to 

 the broader shape of 0. acutirostris ; they differ, however, from 

 the inflexed form of 0. curvirostris which occurs in the Totternhoe 

 Stone. 



The fauna of the limestone beds seen in the Roydon cutting and 

 in the Grimston brook remains to be considered; and, fortunately, 

 the species and the state of their preservation are such that no 

 doubt can possibly exist about the age of these beds. Lithologically, 

 these limestone bands are exceedingly like the hard beds which occur 

 in the Chalk-marl of Buckinghamshire and Oxfordshire ; and had we 

 not found the fossils above indicated, we might have felt very great 

 hesitation about referring them to the Gault. Their lithological 

 characters, however, can easily be explained, for a deep-sea formation 

 of Gault age is not likely to resemble the Folkestone clay ; whereas, 



