CHAP. XI.] HANTONIAN PEBIOD. 211 



water beds. The total thickness at each end of the Isle of 

 Wight is nearly the same (180 feet), but the central marine 

 beds thicken eastward at the expense of the others, and 

 are about 100 feet thick in Whitecliff Bay. The marine 

 band is also largely developed, and still more fossiliferous, 

 near Brockenhurst in Hampshire, so that the deepest part 

 of the estuary seems to have lain to the north and east of 

 the Isle of Wight. 



The succeeding Osborne and Bembridge Beds are a vari- 

 able series of freshwater deposits with one or more layers 

 of estuarine oyster-beds. The Lower Bembridge or Osborne 

 Beds appear to be of lacustrine origin ; at Headon Hill 

 they have at the base a limestone full of siliceous concre- 

 tions, and a similar limestone, associated with calcareous 

 sandstones and ragstones full of freshwater shells, occurs 

 at the eastern end of the island ; the upper beds are red, 

 blue, and green clays, with intercalations of yellow and 

 white sands in the eastern area. These beds were formerly 

 estimated at 60 to 80 feet thick, but have recently been 

 proved to be double that thickness. 



The Bembridge Limestone is a remarkable horizon. At 

 the west end of the island it is a single band of tufa- 

 ceous and concretionary limestone about 15 feet thick, the 

 lower part of which contains freshwater shells, while in the 

 upper part land shells and eggs of the larger snails are 

 found. Toward the east it is split up into several layers 

 of compact creamy limestone, which contain a mixture of 

 land and freshwater shells, and at Whitecliff Bay it is 

 immediately overlain by a marl which is full of oyster- 

 shells. These facts indicate the existence of a large shallow 

 freshwater lake or " broad " on the borders of the estuary, 

 and the gradual deposition in this lake of so much cal- 

 careous matter that parts of it were completely dried up. 

 Moreover, the number of the large tropical land snails is so 

 great that, as Mr. Gardner observes, their presence in such 



