Dedicated 
TO 
ERNEST RUTHVEN SYKES, Esg., F.Z.S., 
Late Secretary of the Malacological Society, 
IN GRATEFUL ACKNOWLEDGMENT OF MOST GENEROUS ASSISTANCE 
RENDERED DURING THE PREPARATION OF THIS VOLUME, BOTH 
IN THE INTRODUCTORY PORTION AND IN THE TEXT. 
MANY OF ITS PAGES TESTIFY TO HIS 
NUMEROUS AND VALUABLE 
CONTRIBUTIONS. 
By HIS SINCERE FRIEND, 
J. C. MANSEL-PLEYDELL. 
