Census of Scottish Land and Fresh- Water Mollusca. 437 



XXXVI. Census of Scottish Land and Fresh- Water Mollusca. 

 By Wm. Denison Eoebuck, F.L.S., Recorder to the 

 Conchological Society of Great Britain and Ireland. 

 (Communicated by the Secretary.) 



(Read 19th February 1890.) 



Daring the past twelve years, under the auspices of the 

 Conchological Society of Great Britain and Ireland, a scheme 

 of authentication and registration of specimens of the land 

 and fresh-water Mollusca inhabiting the various counties and 

 vice-counties of the British Isles has been very successfully 

 carried out. The object being the accumulation of carefully- 

 verified and therefore trustworthy data for ascertaining the 

 actual geographical range of the British terrestrial Mollusca, 

 specimens to the number of many thousands have been 

 submitted to and carefully examined by Mr John W. Taylor, 

 r.L.S., of Leeds, referee to the Society, and in the case of 

 slugs by myself. A few specimens have at times been 

 authenticated by other members of the Society's duly- 

 appointed Committee of Eeferees, but the great bulk of the 

 records have been under the personal examination of Mr 

 Taylor, than whom no one has had a wider experience or 

 more numerous opportunities of studying the land and fresh- 

 water Mollusca of the British fauna. The essential requisite 

 of the authentication system adopted being the personal 

 examination of all specimens sent in by competent and duly- 

 appointed referees, it is obvious that no relaxation of the rule 

 can be allowed without tending to impair the value of the 

 ultimate results, and that no book-records, however trust- 

 worthy, or personal notes unaccompanied by specimens, 

 however reliable the authority, can be entered in the Ptecord- 

 Books. 



The subdivision of the British Isles adopted is the well- 

 known system of counties and vice-counties devised by the 

 late Hewett Cottrell Watson, which is so familiar to every 

 topographical botanist, and which for various cogent reasons 

 is perhaps the most convenient and useful subdivision of the 

 British Islands yet promulgated. We do not dispute that the 



