24 INTRODUCTION. 



Ferussac has observed (Journ. de Phys. 1820) that 

 it is remarkable that in our more northern latitudes, 

 as compared with France, there are found in abund- 

 ance some species, such as Helix Pisana and Bull- 

 mus acutus, which for their size and colour are only to 

 be compared to the French specimens found on the 

 banks of the Loire. 



On the other hand, there are many species, not 

 found in our catalogues, that are common to nearly 

 all the rest of Europe. 



Thus, according to Nilson, 73 of our British 

 species are found in Sweden, and many of them, as 

 for example, 



Helix pygmea. 



fulva. 



rotundata. 



pulchella. 



Zua lubrica, 



at its most northern extremity; and he has, in his 

 Fauna, 16 species which have not yet been found in 

 Britain or Ireland, viz : 



Limax tenellus. 



Helix Udentata Nilson, not Gmelin. 



* fruticum. 



* strigella. 



* incamata. 



* conspurcata. 



* ericetorum Nilson, not Linn. H. candidula 



Studer. 



Clausilia papUlaris, if it is not our C. biplicata. 



* Pupa costidata. 



Paludina Balthica^ if not our Littorina ulvce. 

 octona. 

 similis. 



