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 dower mass of the cre- 
taceous group, called by the French la crate inferieure 
ou ancienne, which in England is designated as the Green 
Sand Formation, or Ferruginous Sand Series.t+ 
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 Ferraginous 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.) The whole series, 
embracing the White Chalk, is now very generally called the Cretaceous Group. 
