248 



W. D. ROEBUCK : LINCOLNSHIRE MOLLUSCA. 



case of a list for a county like Lincolnshire, which has so long lain 

 waste for want of workers, I hold it to be of high importance to 

 draw a clear distinction between what is known and what is sur- 

 mised, hence the distinctive types used. Some time in the future, 

 when all Lincolnshire has been investigated as well and as systematically 

 as Yorkshire and Nottinghamshire have been, a resident conchologist 

 can write a large-type list of its fauna, without giving in small type the 

 evidence upon which he founds it ; but that time has not arrived yet. 



The distinction between 'North' and 'South' Lincolnshire is 

 necessitated by our conforming to the Conchological Society's 

 system of ' vice-counties,' adopted bodily from Mr. Watson's well- 

 known botanical system. The dividing-line is the River Witham 

 from Boston up to Lincoln, continued by the Foss Dyke from Lincoln 

 city to the western or Nottinghamshire border of the county. 



The number of species recorded for the county is 88, of which 

 81 are recorded for North Lincolnshire, and 54 for South Lincoln- 

 shire. The number of species common to both divisions is 47, while 

 34 North Lincolnshire species are not yet recorded for the South, 

 and only seven South Lincolnshire species still remain for discovery 

 in the North. 



The 88 species include 11 slugs, 39 land and 38 fresh-water 

 shells. 



We need not enumerate all the British species which are as yet 

 unrecorded for Lincolnshire, but it will certainly be well to direct 

 attention to some of those more likely than most to be found. No 

 species of Testacella has yet tm'ned up, and there is no other slug 

 which may be expected to occur, unless an example of the very rare 

 TAniax cinereo-7iiger should perchance be found. It is possible to 

 expect Helix fusca^ while Siiccinea elegans, Helix aculeata, Vertigo anti- 

 vertigo, Azeca, Achatina, and Ac?iie will almost certainly reward careful 

 research in suitable habitats. Of fresh-water species it is surprising 

 that Dreissena has not been found in the canals, and Valvata cristata 

 in numerous locahties, and it is quite within the bounds of possibility 

 that Limncea gluiinosa may some day reward the careful searcher. 

 Beyond these any additional species will be of the nature of a great 

 good fortune, and the principal work that now remains to be done 

 for Lincolnshire conchology is to investigate other districts as closely 

 as Louth and Alford have been, and to place the results of all 

 investigations on permanent record. 



The nomenclature of this list is in conformity to the Concho- 

 logical Society's List of British Mollusca ; the arrangement accords 

 more with older systems, and with my own idea of the sequence of 

 the genera. 



Naturalist, 



