217 



THE CENSUS OF THE BRITISH LAND AND 

 FRESHWATER MOLLUSCA. 



By LIONEL E. ADAMS. 



(Read before the Society, June ii, igu2.) 



It would be superfluous to point out the value of a complete Census 

 showing the distribution of each species, and it is to be hoped that the 

 present publication of the Census up to date will show conchologists 

 where the gai)s are that need filling up, and encourage them to assist 

 in the work. 



It will be noticed that Scotland is still very poorly explored, but 

 that the Irish lists, on the other hand, are now very fairly full, mainly 

 through the exertions of Messrs. R. Welch and P. H. Grierson. 



The Society is also specially indebted to Miss Massey, Messrs. 

 C. Wright, C. Oldham, Ue Vimes Kane, A. Shaw and T. Scott. 



It will be remembered that the last Census, which was published in 

 my " Collectors' Manual of British Land and Freshwater Shells," in 

 1896, was the compilation of Messrs. W. Denison Roebuck and John 

 ^V. Taylor — a monument of valuable labour. 



The great merit of the system of authentication is the uniformity of 

 value which it gives to the records, all specimens passing under the 

 eye of the recorder. It does not follow that other records are not 

 equally reliable, but for the sake of imiformity of value it is necessary 

 to confine the tables to such records as have been submitted to and 

 passed by the Society's Referees, otherwise a wide door would have 

 been oi)ened to errors of determination, the avoidance of which is the 

 object aimed at in instituting the authentication system. 



The areas adopted are those proposed by Dr. H. C. Watson, and 

 used by him in working out the distribution of the British Flora. 



It is deemed sufficient to confine the tables to the distrilmtion of 

 species, that of varieties being for many reasons impracticable at the 

 present time. 



Conchologists who can furnish specimens for completing these 

 tables are requested to send them to the Society's Recorder, Mr. 

 Lionel E. Adams, 68, Wolverhampton Road, Stafford. 



Though all specimens will be carefully returned if desired, 

 correspondents are requested to say when sending shells for record 

 purposes whether they wish them to be returned, and thus often save 

 unnecessary trouble of yostage. 



