344 ^rof, Sedgwick on the [May, 



With the exception of the undescribed oyster, all these species 

 are found in exactly the same state of preservation, in the upper 

 marine formation of Colwell Bay. From all these facts, which 

 at first appeared sufficiently perplexing, we concluded ; first, that 

 the London c/aj/ had never extended to Whitecliff Bay, or, at 

 least, had thinned off to such a degree as to be quite insignifi- 

 cant; and, secondly, that the most northern vertical bed of 

 Whitecliff Bay was part of a formation of siliceous sand, &c. 

 between the London clay and the lower Jres/nvater beds. An 

 examination of the Hampshire coast completely confirmed us in 

 this opinion. It has already been stated that the London clay 

 terminates in the cliff nearly opposite the village of Barton. 

 Beds of sand of a light-brown colour there first make their 

 appearance at the top of the cliff, and follow the dip of the infe- 

 rior clay. They are succeeded by other beds of sand, containing 

 two well defined layers of coaly matter which may be traced in 

 the escarpment for a considerable distance. On the last men- 

 tioned sandy strata rests a bed, five or six feet thick, which con- 

 tains a considerable portion of argillaceous matter. The whole 

 system of these beds above the London clay is more than 40 feet 

 thick. The lower sandy strata contain a few marine shells, 

 among which we remarked some very large cerithia; but the 

 highest beds abound in many species which (in addition to a few 

 London clay fossils) form a suite, absolutely identical with that 

 which characterizes the most northern verlical bed of Whitecliff 

 Bay.* At the eastern end of this portion of Barton Cliff com- 

 mences a freshwater formation, resting on the beds last described, 

 and dipping like its associates about ESE. As nearly all thfe 

 fossils I collected from this part of the coast were unfortunately 

 lost, I am compelled to rely almost exclusively on memoranda 

 made by my friend Mr. Whewell, who assisted me in collecting 

 many of the facts detailed in this paper. The notes were, how- 

 ever, taken on the spot ; and are, therefore, we hope, sufficiently 

 accurate to establish the general facts for which we are contend- 

 ing. It appears from what has been stated ; first, that a regular 

 marine formation principally composed of siliceous sand, sepa- 

 rates the London clay from thefreshivater beds of the Hampshire 

 coast; secondly,that the same formation is probably continued with- 

 out interruption from Alum Bay to Whitecliff Bay ; and, thirdly, 

 that the disturbing force which upset the mid region of the Isle 

 of Wight, acted after a part of this formation had been deposited. 

 A deposit preserving the same characters in places which are so 



• It is too much to expect the same phenomena in all the minute parts of a tertiary 

 deposit ; otherwise one might look for a similar suite in the bed (E) which separates the 

 white sand from the lotcer frrshtcatcr formation of Hcaden Hill. (Geol. Trans. voL ii. 

 pi. II.) M'^e last summer only examined this bed in a single point, where it had been 

 exposed by a land slip immediately above the great sand pits. It there contained very 

 little argillaceous matter, but was composed of various coloured sands, which appeared 

 to have been rudely blended together in agitated water. We found no fossils in iti ' > 



