PREFACE. 
There is no branch of Palaeontology of so much importance to the Geologist, as the study of 
Fossil Shells. In this opinion the Author is supported by three of the greatest living authorities. 
Dr. Buckland says—“ Concurrent with the rapid extension of our knowledge of the comparative 
anatomy of extinct families of the ancient inhabitants of the earth, lias been the attention paid 
to Fossil Conchology; a subject of vast importance in investigating the records of the changes 
that have occurred upon the surface of the globe.” Sir Charles Lyell remarks that “ shells 
are hy far the most important class of organic beings which have left their spoils in the 
sub-aqueous deposits, and they have been truly said to be the Models which Nature has chiefly 
selected to record the history of the former changes of the globe. There is scarcely any great 
series of strata that does not contain some marine or fresh water shells.” And again, Buckland 
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justly observes, in descanting on the indispensable utility of the study of Fossils to a thorough 
knowledge of Geology, that “ to attempt an investigation of the structure and revolutions of the 
earth, without applying minute attention to the evidence afforded by organic remains, would be 
no less absurd than to undertake to write the history of any ancient people, without reference 
to the documents afforded hy their medals and inscriptions, their monuments, and the ruins of 
their cities and their temples. The study of Zoology and Botany has therefore become as indis¬ 
pensable to the progress of Geology, as a knowledge of Mineralogy.” And as Mantell truly 
observes, “ the shells of Mollusca, from their durability, often escape obliteration under circum¬ 
stances in which all traces of the higher orders of animals are lost, and they become, therefore, 
of the utmost importance in the speculations of the geologist. In loose sandy strata, they often 
occur in a high degree of perfection; in mud and clay, in a fragile state; in some instances, they 
arc silicified; and many limestones arc wholly composed of shells, cemented together hy calca¬ 
reous spar.” 
When the Author undertook the publication of the following work, it was with a view of 
supplying to Geologists a long-felt desideratum: namely, a work arranged either hi systematic 
or in stratigraphic order, embracing all the species known up to that time, and which might be 
discovered during the progress of the publication. Air. Sowerby’s work, destitute of both these 
advantages, had been discontinued for upwards of nine years, and there was no prospect of 
its being resumed. 
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