168 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. Tebennopliorus includes Vaginulus, Limax in- 

 cludes Arion, Bulimus includes Aehatina, Pupa includes 

 Vertigo, and Clausilia includes Azeca and Oylindrella. 

 Ci/clostoma, which was not given by Mr. Forbes, is added. 

 Besides exhibiting the numerical relations which our 

 species bear to those of Europe, this table also shows 

 the local distribution of the genera. While Limax 

 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. Vttrina, Succinea, and Bulimus are 

 pretty equally diffused. Clausilia is shown to pre- 

 dommate 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 



