298 
GEOGRAPHICAL DISTRIBUTIOlSr. 
They also want some of our smaller ones, as — 
Zonites purus^ Zonites radiatulus^ Zonites excavatus^ Pupa urn- 
hilicata (?), Pupa anglica^ Vertigo alpestris^ Vertigo angustior^ 
Vertigo palustris, Planorbis Icevis^ 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^ Sue- 
cineaputris^ Helix nemorolis. Helix pulchella^ Helix ericetorum^ 
Zonites radiatus^ Zonites cellarius^ Achatina acicula^ Clausilia 
PolpJiii (?), Clausilia rugosa^ Limneeus pereger^ Limneeus 
stagnalis, Limneeus palustris^ Limneeus fossarius^ Limneeus 
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 pulcJiella is the H, minuta of 
Say. 
Zonites nitidus is probably the H. arbor ea of Say. 
Say considered the Paludina vivipara of the two countries 
the same species. 
Air. 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 nemoralL% Canada and U. States ; Helix Jiortensis^ Bos- 
ton ; Helix aspersa, U. States ; Helix virgato^ U. States 
(Ferus.) ; Helix pisana^ U. States (Ferus.) ; Bulimus acutus^ 
U. States (Lesueur). 
Bulimus decollatus 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. 
