JOURNAL OF CONCHOLOGY. 319 



CENSUS 



OF THE AUTHENTICATED DISTRIBUTION OF 

 BRITISH LAND AND FRESHWATER MOLLUSC A 



By JOHN W. TAYLOR and W. DENISON ROEBUCK, F.L.S. 



Read before the Conchological Society, April 16th, 1885. 



With the view of facilitating the labours of the numerous con- 

 chologists and others who are throughout the United Kingdom 

 assisting us in working out the detailed distribution of the 

 British land and freshwater moUusca, and also of those who 

 may hereafter be disposed to assist us by submitting specimens 

 for authentication and record, the following ' census ' has been 

 framed. It is is strictly limited to ' authenticated ' records, 

 that is to such as are verified by specimens which have passed 

 under our own examination. This process secures uniformity 

 of value in the results. 



The numbers are those of counties and vice-counties, as 

 shown on the map which accompanies this article, and defined 

 and explained in the ' Journal of Conchology' for April 1884, 

 at pp. 174 — 184 of the present volume. It will be seen that 

 the Channel Islands are denoted by the cypher ' o ' and that 

 they precede district No. i. The total number of counties 

 and vice-counties for which we have seen specimens is given 

 under each species. 



For the present the distribution of the varieties cannot be 

 given, and some of the doubtful species — such for example as 

 the mythical Arion flavus — are also omitted. 



Conchologists and naturalists generally are requested to 

 aid in filling up the gaps in the records by sending up speci- 

 mens for authentication and study. They will not fail to note 

 how very imperfectly the mollusca of Scotland and Ireland are 

 recorded. 



