PREFACE. 
XI 
to completion. This arrangement was consummated in July 1855 ; and 
thus after a suspension of more than five years 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 he known by the numbers having been added, 
since the printing of the plates. 
