TO 
SAMUEL GEORGE MORTON, M. D. 
MEMBER OF THE AMERICAN PHILOSOPHICAL SOCIETY, 
CORRESPONDING SECRETARY OF THE ACADEMY OF NATURAL SCIENCES, OF 
PHILADELPHIA, &C. 
In publishing the fossil shells of our Tertiary formations, it 
is a pleasure as well as a duty to inscribe to you a work, which, 
whatever its merits, would not have appeared without your en- 
couragement and assistance. Your zeal for establishing the 
Geology of our country on its only permanent basis, organic 
remains, has added a valuable series of American fossils to 
the splendid collections of the Academy of Natural Sciences, 
to which I owe the opportunity to figure and describe nearly 
all the species illustrated in the following pages ; but I sin- 
cerely regret that your professional duties are too arduous to 
permit you to undertake a work for which you are so much 
better qualified than myself ; for, with such ample materials, 
you could not have failed to render it acceptable both to the 
Geologist and the student in Conchology. 
T. A. CONRAD. 
