74 Geological Society. 



Alum Bay ; while other authors have restricted that name to about 

 73 feet of the same section. The age of the Upper Bagshot of the 

 London basin is admitted by all authors to be very doubtful. The 

 only wav to avoid the confusion unavoidable from using the same 

 names for strata the correlation of which was so hypothetical, was 

 to employ local names for both sets of beds. He proposed to refer 

 to the freshwater sands below the Bracklesham and Bournemouth 

 strata, containing a distinctive flora, as " the Studland beds.'* and 

 the sands above the Barton clay by the old name of " the Headon- 

 Hill Sands." 



Above these sands are a series of clays only about 40 feet thick 

 at Whiteeliff Bay, but much thicker at Headon Hill and Hordwell 

 Cliff. These sands and clays form the Headon group ; they consist 

 of freshwater strata with bands of limestone and lignite, but in- 

 cluding numerous inconstant intercalations of layers containing 

 marine shells, for the most part much dwarfed. The age of the 

 Headon group, as shown by the fossils which it contains, is that of 

 " the zone of Ceriihiwm coneavum " of continental authors. 



The brackish-water Headon group is succeeded at "VVhiteclifF Bay 

 by nearly 100 feet of purely marine strata. These marine beds, 

 which had been shown to rest on an eroded surface of the Headon 

 beds, contain the remarkable fauna which had been recognized by 

 many British and foreign geologists as that of the Lower Oligocene. 

 [Similar strata with the same fossils are found in the New Forest, 

 at Lyndhurst, Brockenhurst, Boydon, and other points, and there 

 also attain a considerable thickness. It was pointed out that this 

 marine series is quite distinct from the Headon, or zone of Qenthivm 

 coneavum, with which it had been confounded. 



The author had been very severely criticised for the views which 

 he had put forward in a former paper as to the manner in which 

 the Brockenhurst series is represented in the section at the west 

 end of the Isle of Wight. There was much difficulty in these 

 variable estuarine beds in correlating the beds seen in Colwell Bay 

 with those exposed in the cliffs of Headon Hill. With several pre- 

 vious authors on the subject, he maintained that the great series of 

 sandstones and limestones forming Warden Point and How Ledge 

 are continuous with those exposed in the face of Headon Hill, and, 

 consequently, that the marine beds of Colwell Bay overlying these 

 limestone series are younger than the brackish-water bands interst ra- 

 tified with the Heddon beds of Headon Hill. His critics, however, 

 insisted that these two beds agreed with one another in such a 

 manner that they must be regarded as parts of the same bed. sepa- 

 rated by denudation. In opposition to this view it was pointed out 

 that the Colwell-Bay bed is of the most inconstant character, and 

 long before reaching Headon Hill is seen to be on the point of thin- 

 ning out and disappearing altogether. 



In conclusion, the author pointed out that his own interpretation 

 of the succession and correlation of the strata in the Hampshire 

 basin brings them into complete harmony with that which is main- 

 tained by the great majority of continental geologists, while that of 

 his critics appeared hopelessly irreconcilable with their views. 



