INTRODUCTION 



HE author hopes that this index may prove a real help to the student of 

 Conchology in identifying the British freshwater shells. 



His idea is to present, at a moderate price, a plate of figures, carefully 

 drawn from nature, that will expose the whole group at once, and thus allow a 

 shell to be readily compared with the illustrations. 



By means of a three-fold plate this has been accomplished, and by folding 

 either of the side plates over the middle one the remaining exposed plate has 

 the ' Key ' to it opposite. The ' Key ' to the middle plate is easily referred to 

 by raising the left-hand plate. 



The drawings are, for the most part, of natural size, but where the smaller 

 species have been enlarged, a ' size-line ' has been added. 



In the descriptions of the plates, a colour-column is given, but it should 

 be noted that it refers to the ground-colour of the cleaned shell, and not to the 

 accidental covering of mud, of various hues, found on many shells. Moreover, 

 as even the ground-colour varies in shells of the same species from different 

 localities, too much reliance must not be placed on that alone. 



In the adjoining column some of the main features that distinguish the 

 species from others, somewhat similar, are pointed out. 



With regard to 'habitat,' a great many of the species ma^ be found where- 

 ever there is water, but they undoubtedly show a preference for still or running, 

 shallow or deep, as the case may be. The usual 'habitat' is therefore given. 



In the 'Frequency' column it may be as well to explain that 'local' means 

 the species is confined to certain limited areas, though it may be abundant where 

 it does occur. ' Frequent ' means that the species is not common, but may turn 

 up anywhere, and is pretty well distributed over the country. 



With the exception of some of the chief forms of the variable Limncea peregra, 

 varieties have not been figured, but a descriptive list of them, together with 

 monstrosities, will be found at the end of the book. They have been taken for 

 the most part from Mr. L. E. Adams' "Manual of British Land and Freshwater 

 Shells," to which delightful little book the reader is referred for hints on collecting, 

 cleaning, mounting, and arranging in cabinets these most interesting objects of 

 natural history. 



