298 GEOGRAPHICAL DISTRIBUTION. 



They also want some of our smaller ones, as 



Zonites purus, Zonites radiatulus, Zonites excavatus, Pupa um- 

 bilicata (?), Pupa anglica, Vertigo alpestris, Vertigo angustior. 

 Vertigo palustris, Planorbis Ice vis, and two or three Pisi- 

 dia. 

 On the other hand, many of the British shells find their 



southern limits in France and Germany ; for only 22 of them 



are found in Sicily, and only 17 in Corsica. Of these southern 



species, the greater part, viz. the 18 following, are common to 



those countries, Britain, and Sweden : viz. 



Paludina vivipara, Paludina crystallina^ Bithinia impura, Suc- 

 cinea putris, Helix nemoralis, Helix pulchella, Helix ericetorum, 

 Zonites radiatus, Zonites cellarius, Achatina acicula, Clausilia 

 Rolphii (?), Clausilia rugosa, Limnceus pereger, Limnceus 

 stagnalis, Limnceus palustris, Limnceus fossarius, Limnceus 

 glaber, Anodon cygneus. 

 There are only a very few species of the British land and 



fresh-water Mollusca which appear to be common to the 



American continent. 



According to Ferussac, Helix pulchella is the H. minuta of 



Say. 



Zonites nitidus is probably the H. arborea of Say. 

 Say considered the Paludina vivipara of the two countries 



the same species. 



Mr. Lea considers, I believe truly, that the Unio margariti~ 



fera of the two countries is the same species. 



From the facility with which the land Mollusca can be 



transported during their torpidity, there have been introduced 



into Canada and the United States the following British 



species : 



Helix nemoralis, Canada and TJ. States ; Helix hortensis, Bos- 

 ton ; Helix aspersa, U. States ; Helix virgata, U. States 

 (Ferus.) ; Helix pisana, U. States (Ferus.) ; Bulimus acutus, 

 U. States (Lesueur). 

 Bulimus decoUatus has been introduced into gardens near 



Charlestown, S. Carolina. One of the species, H. aspersa, has 



also been introduced and naturalised in Brazil and some places 



in South America. 



