562 STRATIGBAPHICAL GEOLOGY 



In Whitecliff Bay there is a marine bed near the base of these 

 marls containing Ostrea vectensis, Dosinia incrassata, Nucula similis, 

 and Mytilus affinis. About 50 feet up is a grey sandy limestone 

 (4 feet thick) containing Amphidromus and Glandina, and the 

 highest beds contain Potamaclis turritissima in abundance. 



The recent discovery of the Bembridge Limestone and Osborne 

 Marls on Creechbarrow Hill in Dorset is important as showing 

 that the Oligocene Series extended some distance westward, and 

 that the Bembridge lake must have been a fairly large one. 



The Hamstead Beds cover a large area extending from 

 Yarmouth and Hamstead through Parkhurst Forest and across the 

 Medina River to Brading Harbour. Throughout this tract they 

 maintain a thickness of over 200 feet, and their base is everywhere 

 marked by a baud of carbonaceous clay. At Hamstead the 

 succession is given by Mr. Eeid as follows : 



Feet. 

 Marine Beds with Corbula vectensis, C. pisum, Ostrea callifera, 



Voluta Rathieri, Potamides plicatus, P. elegans ... 31 

 Leaf and Seed Beds. Red and green clays with carbonaceous layers 



containing leaves of palms and water-lilies and seeds . .153 

 White Band. Green clay with white shelly marls ... 6 

 Nematura Beds. Green and black clays with Stenothyra (=Nema- 



tura) pupa, Assiminea conica, Sphcerium Bristovi, HydroHa 



( Tomichia) Duchasteli ........ 64 



Black Band. Black clay with Viviparus lenta and Unio . . 2 



256 



The " white band " is only traceable as far as Parkhurst Forest, 

 but east of the Medina it appears to be represented by a bed of fine 

 sand which, commencing near Newport, thickens eastward till it is 

 about 40 feet and forms a marked feature on the surface. 



D. CONTINENTAL REPRESENTATIVES 



As in the case of the Eocene Series, the Oligocene deposits which 

 are found in Belgium and Northern France can be correlated with- 

 out much difficulty with those of our own country, but those of 

 France include some beds which appear to be higher and newer 

 than any which occur in England or Belgium. Again, in the 

 central part of France there are lacustrine deposits of great thick- 

 ness containing many fossils of great interest and associated with 

 volcanic phenomena. 



1. Belgium 



The Oligocene occupies a large area in Belgium, and though the 

 beds differ considerably in lithological character from those of the 



