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 laevis. 



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 



