ON THE DEEP BORIXG AT RICHATOXD, STTRREI. 



527 



Ammonites crenatus, Brug. 



hecticus, Bein. 



Lamberti, Shy. 



• plicatus ?, Shy. 



(minute forms, possibly young). 



Belemuites, sp. 

 Alaria trifida. 



Gasteropoda (very minute). 

 Astarte, sp. 

 Corbula? 

 Pecten, sp. 

 Pentacrinus 

 MS.)? 



3 Fisheri, Baily {ForheSi 



Pentacrinus, sp. 



Cidaris, sp. (plate and small spine). 

 Acrosalenia(?) (small spine). 

 Crustacean claws and limbs. 

 Bairdia (near to Juddiana, Jones). 

 feerpula vertebralis, Sby. 



, sp. 



Coral (small turbinate). 

 Cristellaria rotulata, Lam. (yar. with 

 cupped centre and raised septa). 



(var. with smooth exterior). 



crepidula, F. (^- M. 



Wood. 



sigmanngensis j 



The evidence of these fossils is conclusive that the strata which 

 contain them are not only of Oxfordian age, but that they belong to 

 the middle portion of the Oxfordian, the Zone of Ammonites hi- 

 mammatus of Oppel or the Zone of Ammonites Lamberti of English 

 authors. 



It thus appears that the Wealden deposits, which have such an 

 enormous thickness (2000 ft.) in the Weald area proper, and are 

 said to have been proved to the depth of 600 feet only 7 miles off 

 at Maidstone, have thinned out completely within 7 miles of the 

 Lower Greensand escarpment. 



For the first time, then, we have direct evidence of the position of 

 outcrop under the Cretaceous rocks of strata of Middle-Oolite age 

 in the South-east of England. The existence of such strata was 

 inferred from the position of the Upper Oolite as revealed in the 

 Wealden boring at Battle, and from that of the Lower Oolites in 

 the borings atKichmond and atMeux's Brewery, and was supported 

 by the fact of the presence of numerous fossils derived from them in 

 the Lower-Greensand strata cropping out from beneath the J^orth 

 Downs. From this evidence we were enabled to indicate with con- 

 siderable precision the exact latitude in the south-east of England 

 where the Middle Oolite might be expected to occur under the 

 Chalk. The Chatham well has supplied the most conclusive evi- 

 dence that our reasonings on the subject were well founded. 



The important modifications of the views hitherto held by geolo- 

 gists concerning the depth at which rocks yielding coal and water 

 respectively may be expected to be found in the south-east of 

 England, which result from the discovery of the wide distribution of 

 Jurassic rocks beneath the Cretaceous strata, have been already 

 dwelt upon, and the justice of the conclusions arrived at has been 

 proved by the important revelations of the Chatham well. 



DlSCTTSSION. 



The President congratulated the authors on the important addi- 

 tions made by these borings to our knowledge of the geology of 

 south-eastern England. He considered that the comparatively high 



Q.J.G.S. i^o. 164. 2p 



