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- 



