78 Geological Society. 



one of the genera, are quite new to this country. A section some- 

 what similar to that of Punfield, is seen at Worborrow Bay. 



In the Isle of Wight, at Compton, Brixton, and Sandown Bays, 

 similar fluvio-marine beds are found at the top of the Wealden, and 

 attain to a thickness of 230 feet. The marine bands here, however, 

 yield but a very scanty fauna. Indications of the existence of beds 

 of the same character and in a similar position are found in the dis- 

 trict of the "Weald. 



While the Purbeck formation exhibits the gradual passage of the 

 marine Portlandian into the freshwater Wealden, the Punneld 

 formation shows the transition of the latter into the marine Upper 

 Neocomian (Lower Greensand). Thus we are led to conclude that 

 the epoch of the English Wealden commenced before the close of the 

 Jurassic period, lasted through the whole of the Tithonian and of 

 the Lower and Middle Neocomian, and only came to a close at the 

 commencement of the Upper Neocomian. 



In tracing the Cretaceous strata proper from east to west, they 

 are found to undergo great modification ; while the Neocomian and 

 Wealden, which they overlap through unconformity, besides being 

 greatly changed in character, thin out very rapidly. 



On stratigraphical and palaeontological evidence, the Punneld 

 formation is clearly referable to the upper part of the Middle Neo- 

 comian. Its fauna has remarkably close analogies with that of the 

 great coal-bearing formation of eastern Spain, which is of vast 

 thickness and great economic value. 



The claim of the Punneld beds, equally with the similarly situated 

 Purbeck series, to rank as a distinct formation, is founded on the 

 distinctness of their mineralogical characters, their great thickness, 

 the fact of their yielding a considerable and very well characterized 

 fauna, and of their being the equivalent of a highly important 

 foreign series. 



2. " Some remarks on the Denudation of the Oolites of the Bath 

 district, with a theory on the Denudation of Oolites generally." By 

 W. Stephen Mitchell, Esq., M.A., E.G.S., of Gonville and Caius 

 College, Cambridge. 



The author briefly referred to the theory according to which 

 oolitic deposits were supposed to have been originally spread out in 

 continuous sheets over the country which they occupy, and to owe 

 their division into separate hills to the action of denudation after 

 their original deposition and consolidation. He suggested, as an 

 equally probable hypothesis, that, whilst the marls and clays of 

 oolitic areas were probably originally deposited in continuous beds, 

 the limestones in many cases may never have extended beyond 

 the areas now occupied by them. He described the beds of lime- 

 stone in the oolitic hills as thinning out towards the valleys on all 

 sides, maintained that the limestones owed their origin to coral 

 reefs, and cited several descriptions of coral islands by Prof. Jukes, 

 to show the agreement in their structure with that which he ascribed 



