200 NEOZOIC TIME. [CHAP. XI. 



and western parts of the Hampshire basin, and through the 

 western and northern parts of the London basin. They 

 consist of clays and sands, which are generally bright- 

 coloured and sometimes contain marine fossils at the base, 

 but in the higher beds plant-remains are the only fossils ; 

 layers of pebbly sand, often compacted into conglomerate, 

 are of frequent occurrence, the pebbles being always of 

 flint. 



2. The second type is that of the Woolwich Beds, which 

 consist of dull or dark-coloured sands and clays, con- 

 taining estuarine and freshwater fossils ; pebble beds of 

 variable thickness also occur in them. This type only 

 occurs over a certain area from Guildf ord in Surrey to 

 Milton in Kent, and again at Newhaven on the southern 

 side of the Wealden anticline ; but it would be rash to 

 assume that it originally extended completely across the 

 Wealden district. 



3. The third type is purely marine, and consists of light 

 grey and greenish sands, with very few pebbles ; it is only 

 fossiliferous in East Kent, but probably passes westward 

 beneath the Woolwich type. 



The first type can be traced into the second along the 

 southern edge of the London basin, and the change con- 

 sists chiefly in the thinning-out of the mottled plastic 

 clays, and the setting-in above them of a bluish-grey 

 laminated clay, which contains freshwater and estuarine 

 mollusca as well as plant remains. Mr. G-ardner has 

 pointed out that the floras of these two clays differ 

 that of the upper clay resembling the London Clay flora 

 more than that of the lower clays and in his opinion 

 the Reading Beds are a distinct group, older than the Wool- 

 wich Beds, and formed in an independent area of de- 

 position. Mr. Whitaker and Professor Prestwich, how- 

 ever, do not agree with this view, and believe the two 

 groups dove-tail into each other. 



