190 GEOLOGY OF THE ISLE OF WIGHT. 



arc chiefly ferruginous sands with iron-stone and 

 concretions of chert, with dark clays in the lower 

 part. The middle group is marked by the preva- 

 lence of green and grey sand with beds of calca- 

 reous sandstones, and cherty limestone called 

 Bcvrgate-stone in Surrey, and Rag in Kent. In the 

 lowermost or Atherfield series, the argillaceous 

 character predominates. The beds of sand 

 abound in peculiar fossils, and the concre- 

 tionary limestones and sandstones contain charac- 

 teristic organic remains. This general notice will 

 suffice, as the details of the sections exposed along 

 the southern coast of the Island, have been worked 

 out by Mr. Webster, Dr. Fitton, Capt. Ibbetson, 

 Professor Forbes, and other eminent observers, and 

 are published in the Transactions and Journal of 

 the Geological Society. 



The following species of shells from the Green- 

 sand of the Isle of Wight, are figured in Plates 

 IV. and V. 



Corbis corrugata, PI. IV. fig. 1. This and the following 



figure represent but one side of the bivalves, and therefore 

 do not convey an idea of the form of the entire shell ; but 

 the markings on the surface are distinctly given, as afford 

 ing the easiest comparison for the inexperienced collector. 



Trigonia caudata, PI. IV. fig. 2. This shell is so remark- 

 aide lioth in its form and sculpture, as to be easily iden 

 tified. 



OervUlia anceps, PI. IV. fig. 3. Entire beds "I' this shell 



