!,-,-> INTRODUCTION. 
In the preceding table, the numbers for Scotland, 
Germany, Sweden, Russia, Switzerland, and Italy, are 
copied from Mr. Forbes's Report ; in the other instances, 
they are taken from the authors named in the table 
itself. Tebemwphorug includes Vaginulus, IAmax in- 
cludes Arion, Bulimus includes Achatina, Pupa includes 
Vertigo, and Clausilia includes Azeca and Cylindrella. 
Cyclostoma, which was not given by Mr. Forbes, is added. 
Besides exhibiting the numerical relations which our 
species bear to those of Europe, this tabic also shows 
the local distribution of the genera. While IAmax 
is most numerous in species towards the north, though 
not in the extreme north, its numbers diminish towards 
the south, until, in Sicily, it appears to be replaced 
by Parmacella. Vitrina, Succinea, and Bulimus are 
pretty ecpially diffused. Clausilia is shown to pre- 
dominate most towards the north, and Cyclostoma with 
equal certainty to prefer the south. Pupa, while it 
flourishes most in northern latitudes, is at the same 
time, partial to mountainous districts. The sixteen 
species which it comprised in Russia and Germany, 
are reduced to seven in the south of France (Landes), 
and to only one in Sicily ; the limited and moun- 
tainous territory of Switzerland affords many more 
species than the whole extent of Germany, which is fur- 
ther north ; and the small province of Como, situated a 
little south of the Alpine ranges, in northern Italy, con- 
tains as many as all the rest of Italy. The genus Helix 
is most plentifully distributed towards the south. In 
