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DEDICATION. 
To His Excellency 
DAVID B. HILL , 
Governor of the State of New York : 
From the commencement of the publication of the Natural History of New 
York, the successive volumes have been dedicated to the Governor of the State. 
In accordance with this custom I have the honor to present to your Excellency 
a new volume of the work, being the second one published under the provisions 
of an act of the Legislature of 1883, being a continuation of the work on the 
Palaeontology of the State of New York. 
This volume, together with one published last year, is devoted to the descrip¬ 
tions and illustrations of the fossil bivalve shells known as Lamellibranchiata, 
and completes the work upon that class of organisms. The two volumes em¬ 
brace the descriptions of all the fossils of this class at present known to occur 
in the higher geological formations of the State, viz.: The Upper Helderberg, 
Hamilton, Portage and Chemung groups, with a small number from the 
Waverly group, which has its chief extension beyond the limits of New York. 
The material has been chiefly collected in the field, or acquired from collections 
previously made during a period of more than forty years. The number 
described in the entire work, from the formations above indicated, amount to 
about 500 species which are arranged under 65 genera, and are illustrated upon 
ninety-six lithographed plates, of which fifty-one are included in the present 
volume. The number and variety of forms is believed to be greater than are 
yet known from the geological formations of the same age in any other part of 
