Every author who attempts a Monograph of any of the departments of
Natural History, must necessarily depend, in a greater or less degree,
upon the kindness and liberality of others. Rare and unique specimens,
particularly of fossil species, are often scattered through different
cabinets, and his work would be rendered very imperfect, if they were
not intrusted to his care. In preparing the following Monograph on the
plan of giving exact models of the species, instead of illustrating
them by engravings in the usual manner, the specimens when used by
the artist are perhaps more liable to accident, and it was at first
supposed that this circumstance might have prevented the original
design. But in no instance, where an application has been made, either
to a public institution or to a private cabinet, has the author met
with a refusal; indeed the courtesy, kindness, and liberality which
he has experienced from naturalists, who have every where aided him
in the prosecution of his work, form no inconsiderable portion of the
gratification which he has received. Besides the acknowledgments to
public museums, and to individuals, which are made in the body of the
work, the author is desirous of recording in this place, the following
cabinets from which he has derived much assistance.