PRKFACE. 



identify some additional ones from Mr. Conrad's notes, and from labelled 

 specimens in the State Collection. 



Ill describing the species, I have preferred to follow the stratigraphical 

 order, beginning with the lowest rock ; considering the geological succession 

 of species to be more in accordance with the design of this work, than a 

 zoological classification. I have nevertheless endeavored, under each rock, 

 to arrange the fossils according to their zoological affinities, beginning with 

 the corals, which are preceded by the marine plants where any are known 

 in the rock. This arrangement has not been so perfc-ct as could have been 

 desired ; but the fiiture volumes will be so planned, by a double series of 

 numbers for the pages, as to admit of being separated, and a complete 

 zoological arrangement of the species made. What we snost need, however, 

 for the purpose of facilitating geological research, is a true representation of 

 the species in their order of succession, arranging always those from separate 

 rocks or groups by themselves. In this manner only can they have their true 

 value affixed to them, and their relative chronological importance assigned. 



The increased number of species over those before known as belonging to 

 these strata, the larger part of which appeared to be new, has made me 

 diffident in advancing the results of my researches, and in claiming, not only 

 a large number of new species, but also a considerable number of generic 

 forms not before recognized. Since the descriptions of species contained in 

 this volume were prepared, and while the early pages were passing through 

 the press, I have had the rare opportunity of several times consulting M. de 

 Verneuil in reference to this part of the subject. His examinations have led 

 to the same result, and he has encouraged me to publish my species as they 

 now stand, assuring me that the greater part are new, and quite distinct 

 from the published European forms. Subsequently I have had the pleasure 

 of submitting some of my specimens, and the results of my examinations, 

 to the learned M. Agassiz, who has honored me by expressing a favorable 

 opinion of my labors. Although, encouraged by such friendly expressions on 

 the part of able naturalists, I have less anxiety than I should otherwise have 

 felt in the publication of the volume, I am nevertheless fully aware that 

 there is much room for improvement. 



Of my scientific friends, and of the scientific public generally, I must ask 

 indulgence, while they consider the circumstances under which the Avork 



