344 ZONES OF THE CHALK. 



" The Middle Chalk may be taken to include the greater part of that formerly known 

 as the Lower Chalk, and will answer to the French Turonian. Its fauna is very diflFerent 

 from that of the beds below, most of the Cenomanian species having died out during the 

 interval marked by the formation of the Melbourn Rock, while other new species were 

 introduced, the chief of these being Ammonites nodosotdes. Am. peramplus, Inoceramus 

 mytiloides, Uhynchonella Cuvieri, Ecldnoconus sulrotundus, Cyphosoma simplex, Cardiaster 

 pygmcBus, and Holaster planus. 



" The Upper Chalk may be regarded as equivalent to the Senonian of the French. 

 It is characterised by the abundance of 3Iicraster coranyuinutn, Cidaris sceptrifera, Tere- 

 bratula carnea, Lima Eoperi, and in the higher zones by Marsupites ornatus, Ecldnoconus- 

 conicus and Belemnitella mucronata,^'' 



