516 EEPORT— 1882. 



The flora of the Aliiin Bay beds is especially distinguished by the number and 

 Tariety of its Leguminosse. The plant-contents of the Lower Bagshot beds of Alum 

 Bay approximate to that of the London clay by the predominance of plants of this 

 family, forty-seven species of which were obtained by Mr. Bowerbauk. 



The junction between the London clay and the Lower Bagshot is clearly seen 

 in Whitecliff Bay, the brown ferruginous clay representing the former, and the 

 latter being represented by pale grey or white sands about 40 feet thick. In the 

 640 feet of these Lower Bagshot beds at Alum Bay no other fossils are known 

 ihan plants, and about 60 species occur. 



Middle Bagshot Series. 



Bracklesham Beds, 



The strata comprised between the sands at the base of Headon Hill, and the 

 pipe-clay bearing sands and clays (Lower Bagshots), overlying the London clay, 

 are subdivided into Barton clay and Bracklesham beds. The Bracklesham beds in 

 Alum Bay are represented by clays and marls in the lower part, and by white, 

 jellow, and crimson sands above. The lower beds are remarkable for the quantity 

 of lignites, coaly or vegetable matter contained in them, constituting beds from 

 35 inches to 2 feet in thickness. The black and coal-like appearance of four of 

 these beds are conspicuous and marked objects in the clifi", and determine the 

 position of the Bracklesham series. 



The uppermost beds of the series, or the yellow, white, and crimson sands, are 

 Hnfossiliferous. At Whitecliff Bay the lower part of the Bracklesham beds are 

 green, clayey sands, containing Venericardia planicosta, Turritella iinbricataria, and 

 Nummiilif.es Icevif/atus. Six zones of fossils are there recognised. A hard bed of 

 conglomerate composed of rounded flint pebbles in a ferruginous cement is also 

 a marked feature in the cliffs at Alum Bay, defining the division between the 

 &acklesham beds and the overlying Barton clay. 



Barton Clay. 



The Barton series, composed of sandy clays and sands with layers of septaria, 

 K sufficiently shown in Alum Bay, where it attains a thickness of 300 feet, and is 

 Tich in fossil remains, the whole of which are marine ; 48 genera and 90 species of 

 mollusca alone have occurred at Alum Bay. 



At Barton Cliff, on the mainland, or opposite coast of Hampshire, a rich and 

 abundant marine molluscan fauna occurs. The lower beds at Alum Bay contain 

 Voluta luctatrix, Rimelln {Rostellarin) rimosa, Conus or Conorbis dormitor, and 

 J'usus longavm, with Crassatella sulcata, &c. 



Upper Bagshot Sands. 



These are the unfossiliferous sands below the Lower Headon beds, used 

 extensively for glass-making, which may be 160 feet thick at Alum Bay. In 

 Whitecliff Bay the junction between the Upper Bagshot sands and the Barton 

 day is sharp and well-defined ; a few casts of fossils occur here, but in so friable 

 a state that they cannot be removed. 



Examination of the clitts at Alum Bay will at once show that the strata from 

 the chalk to the Upper Bagshots are highly inclined, caused by the force that 

 produced the anticlinal axis which traverses the island east and west, and this 

 axis brings to the surface the Wealden beds in Brixton and Sandown Bays, thus 

 revT'alinn' the extent and continuity of the Wealden series, and determining its 

 presence westward in the Isle of Purbeck along the same east and west line of 

 elevation. Eastward of the Isle of Wight this axis is lost under the waters of the 

 English Channel, and we have no visible proof of its influence towards Beachy 

 Head ; it may have aided in preparing a weakened line for the course of the 

 Phannel towards the Straits of Dover. These beds at Hordwell Cliff have been 

 the subject of a notice by Mr. Tawney in the ' Proceedings of the Cambridge 

 Philosophical Society,' and will be referred to in the latter part of my address. 



