20 FLUVIO-MARINE GUOUP 



FLUVIO-MAEINE GEOUP OF THE ISLE 

 OE WIGHT, &c. 



Upper and lower fresh-water formation {Webster). 

 Headon-hill Marls and Limestones {Prestwich). 



The fresh-water formations of the Hampshire basin, 

 extend over the northern part of the Isle of Wight, and 

 the adjoining coast of Hampshire, reposing in both dis- 

 tricts on the London clay. This group consists of nume- 

 rous layers of calcareous and argillaceous marls of various 

 colours, sometimes indurated, alternating with beds of 

 sand, sandy clays, &c. ; and associated with them, are bands 

 of earthy limestone, sometimes siliceous and compact. 

 These beds contain numerous fluviatile and terrestial shells 

 (Bulimus, Helix, Planorhis, Lymnea, ^c), and intercalated 

 with them, towards the middle of the series, are some 

 layers of gi'een sandy marls, sometimes indurated, con- 

 taining marine or estuaiy testacea {Ostrea, Natica, Potam- 

 ides, Melania, ^c). 



The relations of these strata with those in the Paris 

 basin, have long been a subject of great interest ; and it 

 has usually been considered that in the Isle of Wight, we 

 possess a similar sequence of aU the beds above the Cal- 

 caire gi'ossier. 



Mr. Prestwich, however, after a careful examination of 

 this district, and whose memou- contains fall details of 

 the whole subject, has an-ived at a different conclusion. 

 He considers the upper portion of the Parisian series to be 

 wanting in the Isle of Wight, and that the whole of the 

 fresh-water and estuary series of the island are synchro- 

 nous, or nearly so, with the upper calcaire grossier. The 



