NEOCOMIAN OR ATHERFIELD STRATA. 227 



In the upper 250 feet of the greensancl but few 

 organic remains are met with, and the strata are 

 more or less highly charged with peroxide of iron. 

 " Every thing," says Professor E. Forbes, " in this 

 stage, appears to indicate a shallow and barren sea, 

 probably from an elevation of the sea-bottom, pre- 

 vious to a new state of things, when a fresh series 

 of clays, forming the Gait, being deposited, the 

 majority of the animal forms which characterise 

 the clays of the greensand disappear, and are 

 replaced by distinct species, representative in 

 time." * 



Neocomian or Atherfield strata. — The in- 

 ferior portion of greensand at Atherfield, from 

 the lowest bed to the Crackers inclusive, abounds 

 in fossils which are either very rare, or altogether 

 absent in the upper part of the series. A group 

 of subcretaceous deposits near Neufchatel, in 

 Switzerland, having lately been found to con- 

 tain many species of shells not previously known 

 in other parts of the cretaceous system, has, 

 in consequence, been described by some emi- 

 nent French geologists as a distinct formation, 

 belonging to a period antecedent to the de- 

 position of the Greensand, and synchronic with 

 the Wealden ; and they have designated the 



* Geol. Journal, 1845. 



