172 PKOE. J. W. JTJDD ON THE OLIGOCENE 



Bembridge Marls separate the Bembridge Limestone from the 

 Brockenhurst series, and are about 100 feet in thickness. Their 

 fossils are entirely such as lived in fresh water. The Upper Bem- 

 bridge Marls are about 130 feet in thickness (including the lower 

 parts of the beds formerly referred to the Hempstead series), and 

 are much more richly fossiliferous than the Lower Bembridge Marls. 

 Near their base and at a little distance above the Bembridge Lime- 

 stone occurs the band of fine-grained limestone which has yielded 

 to Mr. A'Court Smith such a large number of crustacean and insect 

 remains, some of which have been described by Dr. Woodward* 

 and the Hev. P. B. Brodief. In the higher part of the Upper Bem- 

 bridge Marls there occurs a lignite bed (Black Band) which has 

 yielded a considerable number of plant-remains J. At the eastern 

 extremity of the Isle of Wight the Bembridge group is nowhere 

 exhibited in its entirety, but the thickness of strata above the 

 Brockenhurst series is found to be 220 feet. 



The Lower Bembridge Marls are here about 140 feet in thick- 

 ness, and, as at the western extremity of the Isle of Wight, con- 

 tain but few fossils, and these entirely of freshwater species. But 

 at one point at the east end of the Isle of Wight (namely, between 

 Eyde and St. Helens) these lower beds of the Bembridge group 

 assume a totally distinct character, and are seen as strata of sand 

 and sandstone, occasionally passing into conglomerates. To the 

 upper part of this arenaceous representative of the Lower Bembridge 

 Marls, Prof. Porbes gave the name of the " St. Helen's Sands ;" and 

 the lower part he called the " Nettlestone Grits." The Bembridge 

 Limestone is very constant in character and thickness wherever it is 

 seen in the Isle of Wight. The Upper Bembridge Marls at the 

 eastern part of the Isle of Wight are generally similar to the beds 

 on the same horizon at the west end of the island ; but about 5 feet 

 above the top of the Bembridge Limestone there occurs a band con- 

 taining OstrecE, Cytherea incrassata, and other marine forms mingled 

 with freshwater shells. This band was long confounded with the 

 " Yenus-beds " of Colwell Bay and Headon Hill, its distinctness 

 from these being first established by Prof. Edward Porbes. Only 

 about 80 feet of the lower part of the Upper Bembridge Marls are 

 exposed at the east end of the Isle of Wight. 



Although the Bembridge Limestone is found at Sconce, stretch- 

 ing beneath the sea in the direction of the Hurst-Castle promontory, 

 and isolated exposures of Bembridge beds are seen in Hampshire, 

 yet no continuous sections of the Bembridge group are found in the 

 ]^ew-Porest area. 



The Hempstead series is only clearly exposed at the Hamstead 

 and Bouldnor Cliffs ; but, as pointed out by Mr. Godwin-Austen, 

 there are proofs of the existence of these beds on the high ground 

 covered by Parkhurst Porest§, while Dr. Wilkins has found them 



* Quart. Journ. Geol. Soc. vol. xxxv. p. 343. 



t Proc. Warwickshire Nat. & Arch£eol. Field-Club, 1878. 



I Quart. Journ. Geol. Soc. vol. xviii. p. 369. 



§ ' On the Tertiary Fluvio-marine Formation of the lele of Wight' (1856), p. 37. 



