Mr. Webster on the Strata lying over the Chalk, 181 



Mytilus ------ very different from those of the 



calcaire grossier, 

 Cardium ? 

 Ostrea veslcularis. 



deltoidea. 



Pecten ------ M. Defrance has observed 2 species. 



Crania ------ It was adherent and differing in 



that from known species. 

 Perna ? 



Terebratula, many species. 

 Spirorbis. 

 Serpula. 

 Ananchites ovatus - - - The shell is changed Into calcareous 



spar, and the internal part is con^ 



verted into flint. 

 Spatangus Cor angulnum Kl. 

 Porpites. 

 Caryophyllla 

 Millepora ------ These are often In the state of 



brown oxide of iron. 

 Alcyonia. 

 Shark's teeth. 



§ 2. Lowest Marine Formation over the Chalk. 



The clay and sand cliffs of Alum bay afford one of the most 

 interesting natural sections that can well be imagined. They ex- 

 hibit the actual state of the strata immediately over the chalk before 

 any change took place in the position of the latter. For, although 

 the beds of which they are composed are quite vertical, yet, from 



