438 Proceedings of the Royal Physical Society. 



river-basin division proposed for Scotland by Dr F. Buclianan 

 White is theoretically more scientific, but for practical 

 convenience — quite apart from the very considerable diffi- 

 culty of adapting it to England and Ireland, and the necessity 

 of having a special map for its explanation — it does not 

 divide Scotland into areas small enough and numerous enough 

 for the purpose of showing detailed distribution. 



In pursuance of the system of which I have thus spoken, 

 no less than 28,669 distinct locality-records, each based upon 

 at least one and oftentimes numerous examples, had been 

 authenticated from all parts of the British Isles down to the 

 end of the year 1889. 



• The object of this communication is to summarise the 

 records that have so far been authenticated for Scotland, to 

 brin^ before Scottish naturalists an account of the work which 

 is being done, and to endeavour to enlist their sympathies and 

 their active co-operation in completing it in as short a period 

 as practicable. For this purpose is given under the head of 

 each species all the counties for which it has been authenti- 

 cated by specimens, stating the locality and the name of the 

 person to whom the Society has been indebted for the privi- 

 lege of inspecting the voucher-specimens. In this respect we 

 are placed under great obligation to the numerous individuals 

 whose names appear in this communication. 



The number of records from Scotland has hitherto been 

 comparatively small. Of the total 28,669 records made to 

 the end of 1889, no less than 24,210 were for England and 

 Wales, and only 2187 for Scotland, and still fewer for 

 Ireland. Of course the potential numerical richness in 

 species of an average Scottish county is much inferior to that 

 of an average English county, for climatological and other 

 reasons ; but quite apart from this, considerably less attention 

 has been paid to Scottish than to English land and fresh-water 

 Mollusca. This is shown by the average number of species 

 Cfiven in our books. The 72 counties and vice-counties 

 of England and Wales average no less than 56 species per 

 county, and two of them have actually had 103 and 102 

 species respectively authenticated for them. The average for 

 the 41 counties of Scotland only reaches 33 species per 



