INTRODUCTION. 53 



1. Amphipeplea involuta. 



25. In 1837, Mr. Alder, in his list of British land 

 and fresh- water shells, added 



4. Helix hybrida, as a variety of H. hortensis. 



5. depilata. 



6. limbata, on the authority of Mr. G. B. 



Sowerby. 



26. In 1838, Mr. Alder, in a supplement to his 

 paper on the Newcastle shells, added 



7. Helix sericea. 



8. Vertigo alpestris. 



9. Clausilia dubia. 



10. Planorbis Isevis. 



11. Pisidium cinereum. 



27. In 1838, Mr. Gilbertson, at the meeting of 

 the British Association at Newcastle, added 



1. Alasmodon elongatus, var. Roissyi. 



28. In 1839, Mr. Edward Forbes and Mr. Good- 

 sir gave me, for the Museum collection, from Guern- 

 sey. 



1. Helix aperta, 

 2. revelata. 



The following works and papers treat on British 

 land and fresh- water Mollusca, and have been con- 

 sulted in the revision of this edition. 

 Joshua ALDER. 



Notes on the Land and Fresh-water Mollusca of 

 Great Britain, with a revised List of Species, 

 Mag. Zool. and Botany, ii. 101. (Aug. 1837.) 

 D 3 



