PREFACE. XI 



to completion. This arrangement was consummated in July 1855 ; and 

 thus after a suspension of more than five j^ears on the part of the State, 

 the progress of the work was again authorised. 



This simple explanation, without going into any unnecessary details, 

 or parading in this place the ruinous consequences to myself of this 

 suspension of a work in which I had so heartily engaged and so freely 

 expended my own means, seems required to account for the long-delayed 

 appearance of the third volume. 



In completing this volume, I have endeavored to do all in my power 

 to make it a truthful record of the facts in my possession, and I trust 

 it may be found in many respects more worthy of acceptance by the 

 scientific public than its predecessors. Whatever may be the value or 

 appreciation of this, or of any volumes which may succeed it, the public 

 are indebted for the publication to the unsolicited action, prompted by 

 an enlightened public spirit, of the Hon. E. W. Leavenworth, whose 

 inquiries into the condition of this department were counselled by one 

 of the oldest and most honored teachers of science, and whose action 

 was sanctioned by the approval of several of the most eminent scien- 

 tific men of our country. 



The printing of this volume was begun in 1856 ; and the descriptions 

 of the greater part of the Lower Helderberg species were completed 

 during that year and 1857, when the printing was suspended for nearly 

 a year, mainly to enable me to incorporate in the volume the results 

 derived from the study of the Cumberland and other collections, which 

 are chiefly given under the Oriskany sandstone, and this part of the 

 work was not finished till 1859. 



Some of the plates of this volume were engraved before the comple- 

 tion of Vol. II in 1850* ; a considerable number, between that time and 

 1855, while the work was not in authorised progress, except by the 

 existence of contracts between the State and the engravers. The re- 



• These are chiefly of the Gasteropoda, and may be known by the numbers haying been added 

 since the printing of the phtteg. 



