168 



that the WeaUieii in its present state is not a valley of elevation, — 

 that at some foi-mer ])eriod it has heen an elevated area, but that 

 subs equent changes in the relative positions of the earth's crust have 

 reduced the elevation which this particular portion must have had at 

 a given time, and with reference to other circumjacent areas. 



Numerous sections show that the lowest tertiary strata in the 

 vicinity of the chalk escarpment are comjiosed of rounded pebbles, 

 fine sand, and beds of oyster-shells, the whole corresponding exactly 

 with the Reading and other equivalent deposits. Mr. Austen infers 

 fi'om these facts that the movements of the earth's crust, which have 

 been considered as having been confined to the Wealden district, can 

 be traced into the tertiary area of Surrey and Hants, and that these 

 movements and the process of removal did not commence until after 

 the completion of the lower tertiary series. 



Cretaceous Series. 



The general character of that portion of the chalk which is exhi- 

 bited in the range from Farnham to Dorking, as regards the distri- 

 bution of animal remains, is as follows. Great as is the still remain- 

 ing thickness of chalk in the south-east of England, we must always 

 bear in mind that in every place in which we observe it, it has been 

 extensively abraded and reduced. To what extent this has taken place 

 ■we can only conjecture from such loose calculations as those made on 

 a comparison of the beds of uninjured Hints (such as occur over the 

 surface of the North Downs), and the relative proportion of the flint 

 seams to the beds of pure chalk. 



If we compare the flints which are collected in heaps, either from 

 the fields or dug near the siirface along the North Downs, with such 

 as are to be found in every quarry of the upper chalk, the difference 

 is very striking. In the former every single specimen aftbrds proof 

 that it has been formed round some spongiform body, and this too 

 is evident from the external form. With the flints in situ such forms 

 are rare, and warrant the conclusion that these curious productions 

 were much more abundant in the cretaceous ocean towards the 

 close of that period thixn they had been in an);" other portion. 



A curious fossil, to which Mr. Mantell has given the name of 

 Spotigus, is also not unfrequent in the flint and gravel beds, but 

 has never been observed by the author in beds in situ. 



The most abundant remains contained in the beds, which are now 

 the highest, are Belemnites miicronatus, Pecten nitidus, Ostrea vesicu- 

 laris, Inoceramus cordiformis, Terebratula plicata, Marsupites ornutus, 

 Ananchytes ovatus, together with some undescribed Pec^ews and other 

 bivalve shells. 



Below these beds are found others, with Inoceramus latus. Ventri- 

 culites radiatus, and Coscinopora infundibuHformis in extraordinary 

 abundance, the Catillus concentricus being the most common and 

 characteristic shell. 



Throughout this upper portion of the chalk it is very evident that 

 the layers of flint are the equivalents of the partings between strata 

 in other deposits ; and sufhcient time seems to have elapsed between 



