CRETACEOUS GROUP OF THE UNITED STATES, 

 EQUIVALENTS IN EUROPE. 



Ferruginous Sand. Mr. Vanuxem was the first to de- 

 tect the analogy between this deposit and the chalk for- 

 mation of Europe ; although, as mentioned in the preface, 

 he did not refer it to any particular division of the chalk. 

 My first essay,* published simultaneously with Mr. Va- 

 nuxem's, suggests its analogy to the lower mass of the cre- 

 taceous group, called by the French la craie inferieure 

 ou ancienne, which in England is designated as the Green 

 Sand Formation, or Ferruginous Sand Series. ,f 



My subsequent researches during seven years, have 

 fully confirmed the preceding opinion. 



Calcareous Strata. These were first noticed by my- 

 self in the year 1829. A careful examination of a great 

 number of organic remains has induced me to consider 



*Journ. Acad. Nat. Science, Vol. VI. p. 97. 1827. 



tConeybeare and Phillips describe the Ferruginous sand of England as com- 

 posed of these four subdivisions, counting from below : — 1, Iron sand; 2, Weald 

 clay; 3, Green sand; 4, Chalk Marl. (Geol. pp. 60, 120 &c.j The whole series, 

 embracing the White Chalk, is now very generally called the Cretaceous Group. 



