vili INTRODUCTION 



extent " paper " ones. Misidentifications are not always easily 

 traceable, so that it is frequently necessary to accept a synonym 

 on the ipse dixit of an author who may or may not be correct. 



The species recognized by the compilers are placed under those 

 names, which in their opinion, most nearly accord with the 

 requirements of the International Rules of Zoological Nomen- 

 clature (Monaco edition). The Synonymy of each is ranged in 

 chronological order. The earliest recorded occurrence in the 

 British Islands of each species is noted, as well as its geological 

 range. 



The systematic order adopted is based on the conclusions of 

 trustworthy workers in molluscan morphology, allowance being 

 made for conflicting opinions sometimes displayed by members 

 of the anatomical school. 



Although primarily designed for the use of students of British 

 Mollusca, the work should prove of value to malacologists 

 generally, since most of the genera have a more or less world- 

 wide distribution, while nearly all the species are palaearctic and 

 not a few circumpolar in their range. Moreover, it is hoped that 

 it may have some weight with the ordinary collector and those 

 writers, concerned mainly with the anatomical or palaeontological 

 side of the subject, who are given to undervalue the niceties of 

 nomenclature, not perhaps fully realizing that results correct 

 in themselves but based on inaccurately named specimens must 

 in the end infallibly lead to faulty if not absolutely misleading 

 conclusions, correct systematic determination being the ultimate 

 basis of all zoological science. 



Many friends have kindly assisted in the compilation, more 

 especially are we indebted and would return our sincere thanks 

 to C. Davies Sherborn, of " Index Animalium " fame, to A. E. 

 Salisbury for many bibliographical researches, and to H. W. 

 England, Dr. B. D. Jackson (General Secretary of the Linnean 

 Society), G. C. Robson, J. R. le B. Tomlin, and W. J. Wintle. 

 The late R. Bullen Newton, I.S.O., also gave us valuable help. 



A. S. Kennard. 



B. B, Woodward. 



March, 1926. 



