A MANUAL 



OF THE 



LAND AND FRESH- WATER MOLLUSCA 



OF 



THE BRITISH ISLANDS. 



INTRODUCTION. 



THE great attention paid to the British land andfresh- 

 water shells by Montagu; by my late friend and 

 teacher in zoology, Dr. Leach; and more recently 

 by Mr. Jeffreys, Mr. Jenyns, and Mr. Alder (more 

 especially the latter), has left me little else to do, 

 in revising this edition, than to embody their ob- 

 servations. This is the more peculiarly the case, in- 

 asmuch as they all, in a great measure, worked from 

 the collection now under my charge, which contains 

 the materials used by Dr. Leach in preparing his as 

 yet unedited work on British Mollusca, and, among 

 the rest, the various specimens which I had myself 

 collected when actively engaged in the study of our 

 British species. It is right, however, to add, that, 

 before adopting the remarks of these authors, I have, 

 in every instance where it was in my power (and 

 that was almost universally), verified the facts myself; 

 and, therefore, although I have used their words, from 



