PREFACE. 
Wuen I agreed to assist my deceased friend F. E. Edwards in the task of describing 
the British Eocene Mollusca by taking the Bivalve portion, it was on the understanding 
that the specimens in his collection (which embraced with few exceptions all the species 
known from this Formation) should be placed in my hands, to be retained by me so 
long as they might be required for examination and description, so that I might have 
them constantly under my own eye for study and for comparison with the figures of the 
French Eocene species and other published figures accessible to me. ‘The failure of Mr. 
Edwards’s health put an end to the further prosecution of his portion of the work, viz. 
the Cephalopoda and Gasteropoda, but I was enabled, by the means I have mentioned, to 
issue another instalment of the Bivalvia in the volume of the Palaontographical Society for 
1870. Since then the collection has passed into the British Museum, and by this the 
desideratum which I considered indispensable for the performance of my part of the 
work became unattainable. I therefore gave up the idea of further prosecuting the 
deseription of the British Eocene Bivalvia; but finding that I had in my own cabinet 
several species of Eocene Fluviatile Shells which had not been described, and being 
kindly assisted by Messrs. C. J. Meyer, Caleb Evans, and the Messrs. Bott, with 
the loan of specimens from their cabinets, I essayed to complete so much of the 
work as would comprise the Fluviatile species of the Bivalvia, and with that 
object the accompanying two plates were engraved. Domestic trouble obliged me, 
however, to postpone even this part of the work, and I now find that, owing to my 
advanced age and to the infirmity under which I labour, I am incapable of leaving home 
and spending the time necessary for the thorough study of the species in the British 
Museum which is essential to their satisfactory description. I have therefore, with much 
regret, given up the idea of further describing the British Eocene Bivalve Mollusca, 
and leave its completion to younger and abler hands, confining myself to a description 
of the few species which have been thus engraved, and trusting that, under the circum- 
