218 PROCEEDrNGS OF THE GEOLOGICAL SOCIETY. [Feb. 8, 



divisions over a considerable area a very doubtful and difficult task. 

 In the present paper I propose to include in the Punfield formation 

 those beds at the top of the series which present the same mineralo- 

 gical characters as the typical beds of Punfield Cove, and which, 

 like them^ show signs of Jftivio -marine origin in their intercalated 

 bands of marine shells. The great mass of variegated strata con- 

 taining only freshwater and terrestrial fossils I regard as the Wealden 

 proper. 



1. Brixton Bay. The Punfield strata are seen here between 

 Atherfield Point and Barnes High. They are well illustrated in the 

 detailed section of Professor E. Forbes and Mr. H. W. Bristow *. 

 Their junction with the overlying " Perna-beds of the Upper Neo- 

 comian " is fully described by Dr. Fitton, who had a favourable 

 opportunity for observing it in 1847 1 ; this junction is now con- 

 cealed. The Punfield strata of the Isle of Wight, which attain a 

 thickness of 230 feet, fall naturally into two groups, which, for the 

 sake of convenience in description, I have distinguished by local 

 names (see vertical section, fig. 3). 



A. The Cowleaze Series, consisting of dark grey, blue, or green 

 cypridiferous shales and clays, with indurated sandy ferruginous 

 and argillaceous bands, and thin beds of limestone crowded with 

 shells, Paludina, Cyrena, Cerithium, Melanopsis, Unio, &c. " Beef," 

 or fibrous carbonate of lime, occurs abundantly in these limestones, 

 Avhich not unfrequently contain marine shells, and are sometimes quite 

 made up of small oysters, when they exactly resemble the well-known 

 " Cinder -bed " of the Purbeck series. It is evident that the 

 Cowleaze series was deposited under conditions very similar to those 

 which prevailed during the formation of the Purbecks. "While, 

 however, in the latter the clays are subordinate to the limestones, 

 in the former the limestones are much less developed than the clays. 

 The thickness of the Cowleaze series is about 180 feet ; and the best 

 exposure of it is in Cowleaze Chine, where nearly 100 feet of its 

 lower portion is exhibited in a clear section. The Cowleaze beds 

 contain in places plant-remains ; and in someof the bands teeth and 

 scales of fish are very abundant. Among the marine shells occur 

 Exogyra sinuata and K Boussingaultii, both much dwarfed, also 

 Modiola (two species), Carclium, and Oerithium. I am not aware 

 that any Ammonites have been found in these beds in Brixton 

 Bay, though an undoubted specimen was obtained from them at 

 E.ed Cliff in Sandown Bay. The limestone bands of the Cowleaze 

 series are used locally, like those of the Purbecks, for rough 

 paving. 



B. The Barnes Series. These beds rise from the shore at Cowleaze 

 Chine, and crop out at the surface at Barnes High. Owing to the 

 superior hardness of their upper beds they make a very marked 

 feature and can easily be traced inland through the island. While 



* Memoirs of the Geological Survey, Geology of the Isle of Wight (1862), 

 plate 2. fig. 2. 



t Proc. Geol. Soe. vol. iv. p. 198 ; Quart. Journ. Geol. Soe. vol. iii. p. 293. 



