98 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



where there is a considerable thickness of mottled clays, capped by 

 a thick pebble bed similar to that at Blackheath, and underlaid by 

 2 to 3 feet of sand with the Ostrea Bellovacina. 



At Epsom the Thanet Sands commence : at least it is to that de- 

 posit I would refer the lower beds (iii.) in the following section on 

 the railway, half a mile north-east from that town. 



1 /I 



Fig. 6. — Railway Cutting, Epsom. 



Feet. 



'd. Brownish sand 3 



Green sand 2 



b. Coarse yellow and green 

 sand with flint-pebbles 



I ill its lower part 4 



■™»yiiw|wiiaeiiM' [a. Laminated grey clay 1^ 



Chalk . ^> ~ 'ill, „__r__ _^ fc. Fine white sand 12tol5 



" ^X=. III. -{ 5. Grey sand 2 



Green sand and flints ... Of 



Near Ewell the mottled clays are worked at Nonesuch Park, but 

 the section is very imperfect. 



Thus far the middle division of the " Lower London Tertiaries " 

 consists entirely of sands and mottled clays (with a comparatively small 

 quantity of flint-pebbles at their base), remarkable for the absence 

 of organic remains, excepting a bed of the Ostrea Bellovacina com- 

 mon, but not constant, in the thin stratum of sand and pebbles re- 

 posing immediately upon the chalk. We now, however, arrive at a 

 point where a very considerable, and rather sudden, change takes place. 

 Thick masses of rounded flint shingle, alternating with sands and less 

 frequently with grey and carbonaceous clays often laminated, and 

 characterized by a peculiar estuarine and freshwater fauna, now 

 intervene between the "Basement-bed of the London Clay " and the 

 " Thanet Sands." Into this mass the mottled clays, however, occa- 

 sionally dovetail in a manner sufficiently clear to show the relation 

 and synchronism of these two very distinct-looking groups. 



This change takes place nearly on a line passing N. and S. 

 through London. The Diagrams A. and C. PL I. exhibit the leadina; 

 phsenomena. The following sections will serve further to show the 

 connection of these two groups of strata. It will be seen that the 

 mottled clays do not hold, as might be supposed from some of the 

 sections around Blackheath, any definite position either above or 

 below the Woolwich fluviatile beds, but that they alternate with the 

 whole series, sometimes appearing only above and sometimes only 

 below the latter, and at other times both underlying and overlying 

 them. 



At Croydon there is no complete section of these beds, but the 

 following may be considered as the approximate sequence at Park 

 Hill, on the east of that to-w^i. It has been taken, with ^Ir. Flower's 

 assistance, on difl'erent occasions when the several beds have been 

 separately and partially exposed. 



