33 INTRODUCTION. 



2. Helix lamellata, discovered by Mr. Bean at 

 Scarborough, and found by Mr. Alder at New- 

 castle, and lately in North Germany. 



3. Zonites purus, discovered by Mr. Alder, near 

 Newcastle, where it is not uncommon. 



4. 5. Zonites excavatus and Pupa Anglica, also from 

 Scarborough. 



6. Vertigo alpestris, found by Mr. Gilbertson of 

 Preston, at Clithero, in Lancashire, and by Mr. 

 Thomson near Newcastle. 



7. Clausilia dubia, common in Yorkshire, at New- 

 castle, and in Lancashire. 



8. 9. Planorbis Icevis and Pisidium cinereum, both 

 found in ditches, and often together, near North 

 Shields. 



There are one or two species whose distribution 

 appears more to depend on the nature of the country 

 than the climate. Thus, the Alasmodon elongatus is 

 found in the mountain streams of Wales, Cumber- 

 land, Scotland, and Ireland, and the variety A. e. 

 Roissyi is found in similar situations in Yorkshire and 

 Scotland. 



In Irish lakes there has been found by Mr. Har- 

 vey Amphipepilea involuta, which is very different 

 from the English ones. It is to be hoped that this 

 is only a forerunner of several other species which 

 will hereafter be found in that very interesting and 

 but little investigated country. 



It is probable that many of the species here indi- 

 cated may have a much more extended range ; for 

 had this sketch been written a very few years ago, many 

 species, such as Helix fusca, H depilata, Bidimus 

 Lackamensis, Azeca tridens, Pupa edentida, Acmefusca, 



