INTRODUCTION. ix 



To the several conchologists and laborers in other departments of Natural History, 

 with whom they have more or less freely communicated, and from whom they have 

 received occasional suggestions, they desire to express their thanks, without having 

 it thereby understood that any of these gentlemen are responsible for conclusions 

 finally adopted. Those to whom their acknowledgments are more especially due 

 are. Dr. Wm. Stimpson, and Prof Theo. GUI, of Washiugton, D. C. ; Dr. A. A. 

 Gould, of Boston; Dr. Isaac Lea and Mr. Geo. W. Tryon, of Philadelphia; Dr. 

 P. P. Carpenter, of Warrington, England ; Mr. W. G. Binney, of Burlington, New 

 Jersey; Mr. J. G. Anthony, of Crnciimati; and Mr. Temple Prime and Thomas 

 Bland, of New York. 



Most of the published works on Geology, Palaeontology, and Conchology have 

 been consulted during the preparation of the work, and a list of these wUl be 

 appended to one of the succeeding parts. 



