PREFACE. 
In publishing the present work, I hope to add some new 
facts, contributing to the development of the geology of our 
country. Little, comparatively, has yet been accomplish- 
ed in defining with perfect accuracy, most of the beds of the 
great geological masses of our extended formations; and 
these contributions are presented with a view to assist, 
though in a small degree, in the accomplishment of an 
object desirable to every American geologist, a perfect and 
thorough knowledge of American geology. 
Presuming the species to be new, I have endeavoured to 
make minute descriptions, accompanied by faithful figures 
of each, with the hope of determining their characters per- 
manently. 
The small contributions at the end of this volume are 
added, in the hope of their proving to be of some interest, 
the specimens having been for some years in my possess- 
ion, without a favourable opportunity before presenting 
itself for their publication. 
Having last spring, after my return from Europe, finish- 
