126 (4EOLOOY OF THE ISLE OF WiaHT. 



consider the Headon Hill series as the upper portion of the 

 Barton group, and, as such, to refer the whole to the Calcairc 

 grossier. 



In the autumn of 1846 Prof. Prestwich communicated a paper 

 " On the occurrence of Cypris in a part of the Tertiary Strata 

 of the Isle of Wight,"* to the Geological Section at the Meeting 

 of the British Association at Southampton. 



The place from wliich these fossil C^ypridae were obtained was 

 the upper part of Hamstead Clift, near Yarmouth. The author 

 gives a section of the beds, which will be found to agree most 

 accurately with the description contained in the subsequent por- 

 tion of this Memoir, and notes the genera of the included shells, 

 adding " We have thus in the lower pari of the section a deposit 

 containing essentially freshwater testacea, becoming more mixed, 

 as we ascend, with shells frequenting estuaries. It is a 

 singular feature of this group, which I believe to form the upper 

 beds of the freshwater formation of the Isle of Wight, that a 

 large portion of the species occurring in it are new ; thus the 

 two characteristic fossils are a species of Potamides and a 

 Melania, neither of which do I find described. The Cypris also 

 is peculiar to this locality." From the passages here quoted it 

 will be seen that Professor Prestwich had the clue to the structure 

 of the Upper Tertiary series of the Isle of Wight, and that time 

 and opportunity were alone wanting to enable him to work out 

 details on which the Bembridge and Hamstead groups were shortly 

 afterwards shown by Forbes to be clearly separable from the 

 Headon series, with which they had continued to be confounded. 



In 1853 Forbes publishedf an outline of the results of his 

 work in the Isle of Wight between the years 1848 and 1853. In 

 this paper he gave a new reading of the succession, and a revised 

 classification and nomenclature of the beds. This was followed 

 in 1856 by his posthumous memoir "On the Tertiary Fluvio- 

 marine Formation of the Isle of Wight,"t and in 1862 by the 

 first edition of the present Memoir. 



The only subsequent criticism tending in any way to contra- 

 dict the work of Forbes was contained in a paper by Prof. Judd.§ 

 This author maintained the correlation of the Headon Beds 

 at Headon Hill with those of Totland and Colwell Bays to be 

 erroneous and stated that " the strata exposed at the base of 

 Headon Hill are not, as supposed by previous observers, a mere 

 repetition, through an anticlinal fold, of the beds seen in Colwell 

 and Totland Bays, but are on a distinct and lower horizon than 

 the latter. These Headon-Hill beds are also foimd to contain a 

 different assemblage of fossils from that which characterizes the 

 Colwell and Totland Bay beds." Prof. Judd also proposed a new 

 classification of the Oligocene Beds, in which they were divided 



* Report Brit. Assoc, for 1846, p. 56 (^Candona Forbesii, T. R. J. in Prof. Prest- 

 •wich's Collection). 



f Quart, .lourn. Geol. Soc, vol. ix. p. 259. 



j Memoirs of the Geological Survey. 



§ Quart. Jtmrn. Geol. Soc, vol. xxxvi. p. 137. (1880.) 



