1s INTRODUCTION. 
The greatly extended Tertiary deposits on the Atlantic 
coast of our country, present one of the most interesting 
of the geological phenomena known in it. To ascertain 
the relative age of the deposits of the same formation in 
Europe, has engaged the attention of the fossil concholo- 
gist there for many years. With us, partial examinations 
of the fossils of the different beds, have already been made 
by several of our geologists. In the course of my inves- 
tigations, I have satisfied myself of the identity of our 
Tertiary Formation with that of Europe. 
After a careful examination of a great number of genera 
and species, from the Tertiary of Claiborne, Alabama, I 
had no hesitation in referring them to the same period as 
the London Clay of England and the Calcaire Grossier 
of Paris; although this deposit is composed of silicious 
sand, while that of the London Clay is argillaceous, and 
the Calcaire Grossier is calcareous. This part of the Ter- 
tiary Formation, as before stated, is called by Mr Lyell, the 
Eocene Period. It abounds in the greatest variety of 
fossils ; one thousand two hundred and thirty-eight species 
of shells having in Europe, as before mentioned, been 
noticed in it. I have already observed nearly two hundred 
and fifty species from Claiborne, descriptions of two hundred 
and nineteen of which being supposed to be new, will be 
found in their proper order, in this memoir and its supple- 
ment.* It is an extraordinary fact, that among the whole 
of these, there cannot be, with absolute certainty, a single 
species found to have its analogue in a living species. Some 
* Mr Conrad has described twenty-five species. See Fossil Concho- 
logy, Nos. 1 and 2, and the American Journal of Science and Arts, vol. 
23, p. 339. 
