2 PREFACE. 
altered, and the known Eocene Mollusca intended to be comprised in his work have since 
then been so largely augmented in number, as seriously to impede his progress, and 
to compel him to change his original intention. The prospect once entertained by Mr. 
Edwards of completing the whole of the Eocene Mollusca thus became so remote that 
he proposed to me that, as my monograph on the Crag was finished, I should describe 
the Bivalves of the older Tertiaries. 
From a knowledge of the amount of labour my friend has before him ere he 
reaches the termination of the Univalves, which must occupy him for many years to 
come, 1 was induced to consider whether any assistance that I could render in the 
illustration of these fossils would not be of service to the science of Geology. I felt 
at first especially reluctant to interfere in any way with a work that has been so 
ably conducted, but the great desire expressed by Tertiary Geologists to possess an 
illustration of the Mollusca of the Eocene period in this country still unfigured and 
undescribed was an inducement to make all other considerations subordinate to that 
imperious want, and on that ground alone I have consented to attempt to supply 
such a desideratum. Mr. Edwards has in the most liberal manner promised to place 
the whole of his Bivalves in my hands, as they may be wanted for examination. Tis 
collection of these fossils is the most perfect I have seen, and as the work was intended 
to be done by himself, the type specimens have and will be taken from his cabinet, except 
where otherwise particularly expressed ; and the principal localities will be introduced on 
his authority. Mr. Wetherell, Dr. Bowerbank, Mr. Prestwich, the Rev. Osmond Fisher, 
and all my geological friends, haye most kindly permitted me the use of any specimens 
in their cabinets, and I have to return them my best thanks for their assistance, with- 
out which my work would be very incomplete. Mr. Wetherell’s collection is parti- 
cularly rich in the fossils of the London Clay from the north side of London; and Dr. 
Bowerbank’s more general collection possesses some choice and unique specimens. ‘To 
Mr. Prestwich I am further indebted for some of his typical specimens, and more 
especially for his assistance in regard to localities. Neither must I omit to mention 
that our national museums contain many specimens that have already been used 
for the illustration of the Bivalves of these older Tertiaries, or which will materially 
contribute to that object; and I beg to express my obligations to the conservators of 
these treasures, who have in the most handsome and friendly manner given me every 
possible facility and assistance in the promotion of my undertaking. The utmost desire 
of every one connected with Paleontology appears to have been shown to assist in 
forwarding the good work undertaken by the Palzontographical Society. 
S. V. WOOD. 
March, 1861 
