172 



shells are abundant in these nodules ; indeed these beds seem richer 

 in organic contents than any other portion of the cretaceous series : 

 good specimens however are difficult to obtain, as the outer surfaces 

 of the shells adhere very strongly to the matrix. 



Besides the fossils contained in the calcareous nodules, the inter- 

 mediate clay-beds contain in great abundance a large oyster, with a 

 coarse foliaceous structure. These beds form the lowest portion of 

 the cretaceous series in this part of England, and are either peculiar 

 to this locality or have been overlooked elsewhere. 



A like argillaceous division occurs at the base of the greensand 

 escarpment of the great valley of the Weald, where also it advances 

 in the shape of an under terrace. At Parkhatch, near Hascomb, 

 these beds were cut through in digging a well, and found to rest 

 upon blue Wealden shales. 



Strata have been described by some of the French geologists, 

 which correspond exactly in position, mineralogical character, and 

 included fossils with the argillaceous group above noticed. The 

 French strata occur at the base of the cretaceous series of the Paris 

 basin, and are described by Mons. Leymerie and Cornuel under the 

 names of the argile ostreenne, and the calcaire cl Spatangues, and 

 belong to their Neocomian group. On this subject Mr. Austen has 

 the following remarks : — 



In thus comparing the lowest argillaceous division of the green- 

 sand of the south-east of England with the Neocomian group of con- 

 tinental geologists, it may be well to consider what is the value 

 of that group, and how far it has hitherto been recognised in this 

 countiy. The fossils of the upper Neocomian beds of Vassy and the 

 department of the Aube are forty-two, of which only one (the Cor- 

 bula pnnctum of Phillips) is regarded as an English species, and even 

 that is quoted with a doubt. So far, then, the establishment of an 

 additional group to the cretaceous series, as described by English 

 geologists, has been strictly in accordance with the principles on 

 which most recent divisions have been made in older rocks ; and in 

 the absence of figures and descriptions of some of the remarkable 

 shells which this group contains, the continental geologists very na- 

 turally concluded that it was wanting in the English series, an 

 inference which has led to some erroneous generalisations. 



The grounds on which this subdivision is proposed are the fol- 

 lowing : — 



1 . Distinct mineralogical characters, in a constant position in the 

 series ; in which respects it is of the same value as most other geolo-. 

 gical arrangements. 



2. Agreement in this respect with the nearest portions of the cre- 

 taceous series in France. 



3. Its position beneath the lowest portion of the series which is 

 to be found described in woi'ks on the subject. 



4. A distinct and peculiar suite of organic remains. — 

 Ostrsea, n. s. common. Corbula punctum. 

 Pholadomya neocomensis. Astarte beaumonti. 

 ■ ■ solenoides. ■' • substriata. 



