VOL. XVII. (2) LAND AND FRESH-WATER MOLLUSCA 179 



accidentally introduced in cotton-bales, but it appears to be 

 well established and spreading rapidly. Hdicella elegans, on 

 the other hand, although it appears to thrive in one small 

 spot near Dover, refuses to live elsewhere. None of these 

 emigrants are likely to be found in the county, at any rate 

 for many years to come. Of the remaining 144 species, 102 

 have already been taken in the county, and it is not improbable 

 that further search may result in some six to eight additional 

 forms eventually being found. 



The Pisidice are very difficult to determine, and there 

 are very few conchologists who will venture to identify them 

 with certainty. The list, so far as regards that genus, must 

 therefore be understood to be provisional only, although 

 I believe that so far as it goes it is correct, and that if any 

 alteration be found necessary, it will be by way of additional 

 species. 



The only other form which appears to call for special 

 remark is Vivipara contecta var. inflata Villa. This remarkably 

 fine shell has not been found anywhere in England except in 

 the Thames and Severn Canal near Chalford, where I was 

 fortunate enough to find a number of examples. The shells 

 were submitted to Mr John W. Taylor, of Leeds, the author 

 of the " Monograph of the Land and Fresh- water MoUusca of 

 the British Isles," who identified them with the Italian variety 

 named above. 



In the subjoined list I have used a good many varietal 

 names. The advisability of using varietal names may possibly 

 be questioned ; they are, however, of general use among concho- 

 logists, and certainly have their uses in facilitating reference 

 to the very mariy forms which are known. All varietal names 

 have not the same weight, but all those varieties which are 

 enumerated below have, I consider, sufficiently well-defined 

 characters in common to justify the use of the names. I do 

 not pretend that the names which I have used are exhaustive, 

 and it is very probable that a conchologist who carried sub- 

 division to an extreme limit would considerably extend the 

 list. It is, of course, open to any person who prefers not to 

 use varietal names to disregard them. 



