174 HELICIDJB. 



only comprises those species which are more or less 

 globular and have usually a semilunar mouth. But the 

 line of demarcation seems to have been drawn close 

 enough when it excluded those species having turreted 

 shells, such as the Bulimi, which only differ from some 

 of the Helices in the spire being a little more produced. 

 The number of British Helices is not sufficiently large 

 to justify the artificial separation, by some conchologists, 

 of a few species which have a depressed spire and a 

 more or less complete peristome, under the generic 

 titles of Carocolla or Chilotrema, and Zurama or Am- 

 plexus otherwise Vallonia. 



Three species of Helix appear to have lived in this 

 country during the glacial era ; but they have since 

 become extinct, or at any rate have not been noticed by 

 any writer on British Conchology, although they are all 

 of a tolerably large size. Their shells are found in the 

 upper tertiary beds of our Eastern counties. They have 

 survived and still exist in the northern and temperate 

 parts of Europe. One of these species is the H. ruderata 

 of Studer, which ranges from Siberia and Lapland to the 

 alpine districts of France and Switzerland. Another is 

 the H. incarnata of Miiller, which does not seem to 

 extend quite so far north, but inhabits Sweden, Germany, 

 France, Switzerland, and Lugano. Mr. Daniel informs 

 me that he has found it in the Loess at Baden. The 

 third species is the H. fruticum of Miiller, which is found 

 living in every part of the European continent between 

 Finland and Switzerland, and (according to Gerstfeldt) 

 also inhabits Siberia and the Amoor territory. Mr. 

 Searles Wood has recorded this last species as a pliocene 

 fossil in consequence of his having found an imperfect 

 specimen at Stutton ; and I lately detected it in the 

 lacustrine bed at Mundesley. 



