INTRODUCTION. 25 



Cyclas lacustris. 



Unio ater. 



* crassus Nilson. U. littoralis Lam. 



limosus. 



And of these at least half (those marked with a star) 

 are also common to France and to Germany ; and this 

 may be the case with some of the others. Some of 

 these species (of Helix for example) are of a size 

 as large as H. hortensis and H. rufeseens ; and the 

 largest, as H.Jruticum, H.strigella, and H.candidula, 

 are found as far south as Vienna, and H. incarnata 

 as far as Italy. Indeed, some of the continental con- 

 chologists appear to upbraid our idleness in not having 

 found them in England, where, probably overlooking 

 our insular position, they assume that these species 

 ought to be found. 



Nearly three fourths of our species, that is to say, 

 91 out of the 126, are recorded by Pfeiffer as inhabit- 

 ing Germany ; and the Germans have 80 species which 

 are wanting to our Fauna ; but it is remarkable that 

 they have not some of our larger species, as 



Limax carmatus^ 



Helix limbata^ 



fusca, 



Piscina, 



granulata, 



Amphipeplea glutinosa, 



Segmentina lineata. 

 They also want some of our smaller ones, as 



Zonites purus, 



radiatulus, 



excavatus, 



Pupa umbilicata (?) 



c 



