03 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 4, 



2nd volume of the Society's Jom-nal, in his paper on the Isle of 

 Wight Tertiaries. I have compared his section with the beds on 

 the spot, and found it very correct. But, inasmuch as some parts of 

 the series seem better exposed at the present time, and since my 

 object in this paper is more especially to distinguish the fossiliferous 

 heels, I shall give a part of his section somewhat more in detail 

 (fig. 1), together with lists of fossils made from my own observation. 



The Bracklesham Beds resting on the Lower Bagshot Sands may 

 be considered to commence in ascending order with IS'o. 6 of Mr. 

 Prestwich's section, where their base is a bed of rolled flint-pebbles, 

 from 10 inches to a foot in thickness*, incomparably the most 

 marked bed of pebbles in the section. Immediately above the 

 pebbles imj)ressions of bivalve shells occur in clay ; they are scarce, 

 and difficult of determination. One looks like a Cytherea, and 

 another like a Tellina. But their presence is interesting, because 

 the next 200 feet of sands and finely laminated clays and sands 

 contain apparently no organic remains except vegetable imj)ressions 

 and lignite. A thin band of impure pipe-clay may be made out in 

 this part of the series, with vegetable impressions very inferior to, 

 but possibly corresponding with, the leaf-bed of Alum Bay. 



There is much difficulty in fixing here a superior limit to the 

 Bracklesham Beds. It is true that the series is complete ; but the 

 highest fossiliferous bed which can be satisfactorily made out un- 

 doubtedly belongs to the Bracklesham series. 



Above this we do not know our whereabouts for certain, until we 

 reach the Headon Sands. The intervening beds are badly displayed, 

 and appear to contain very few fossils, and those not very typical. 

 Provisionally, No. 18 of Mr. Prestwich's section t may be taken to 

 represent that stratum of the Barton series usually known, as the 

 '^ High Chff Sand ;" and then No. 19, and possibly part of the Sand- 

 bed No. 20, which Prof. Forbes found to contain " abundant impres- 

 sions of marine shells, apparently of Barton species ":j:, will represent 

 the upper part of the Barton series §. It will be seen that the strata 

 of No. 17 of Mr. Prestwich's section are much obscured by the con- 

 dition of the cliff. If we give the whole of this portion to the 

 Barton series, we shall not be able to allow as much thickness to 

 the superior part of the Bracklesham Beds as the Stubbington section 

 and the New Forest beds would lead us to attribute to them. It 

 therefore seems most probable that the line of separation at this 

 place is to be sought somewhere in the concealed portion of No. 17 

 (No. XIX. of the following section). The upper part is probably the 

 equivalent of a bed near the base of the Barton series, which is 52 

 feet thick at Alum Bay, and at that place very fossiliferous, having 

 been formed under a less deep-water condition. The next portion 



* A pebble-bed, forming tlie base of tlic Bracklesham series, is very fully 

 developed at Bishopstoke. See Geol. Survey Map, sheet No. xi. 



t See Quart. Journ. Geol. Soc. vol. ii. p. 254. 



\ Memoirs of the Geol. Survey, Isle of Wight, 185G. 



§ Even at Alum Bay the dark clays of the central portion of the Barton series 

 are replaced by sands. 



