XV111 INTRODUCTION. 



With regard to the shells merely, there is very little more to be 

 made known, but a reclassification of the family Zonitidse, based 

 upon all the characters of the animal and the shell combined, is 

 very desirable. There is so much to be done that it seems even 

 now somewhat premature to bring out this volume, the more so 

 as it deals principally with the above-mentioned family and 

 because our knowledge of the Pulinonata (the Land-Mollusca of 

 India) is far behind our knowledge of any other group among the 

 Invertebrata. This is due to the fact that until comparatively 

 recently the shell only, and not the animal that constructs it, 

 has been taken into consideration. It is well known that the 

 building up of the shell is a process performed invariably in the 

 same way by one part of the animal. 



These neglected forms of life are found by those who will 

 examine them to differ, generically speaking, widely one from 

 the other. It will be seen in the following pages that a very 

 large number of them have never been examined at all, so that it 

 is still doubtful to what genus many of them should be assigned. 

 Any satisfactory conclusion therefore regarding their phylogeny 

 is impossible and regarding their distribution most uncertain. 

 In examining the shells alone we find in several genera these are 

 so extremely alike, the differences so subtle that the eye fails to 

 appreciate them. Again, the uncertainty regarding habitat is 

 increased in some cases by the types being lost ; in others by the 

 doubtful authenticity as to habitat of their representatives in 

 museums. Occasionally three different species may be found in 

 one tablet under the same name, and these from two or more 

 localities. In such cases it is only by collecting de novo in the 

 localities where the types were procured that we can be certain of 

 absolute and true identification. 



Only the families Testacellidse and Zonitidae are included in 

 this volume. 



The classification adopted has been that employed in the 

 manuscript left by Dr. W. T. Blanford, which was the subject of 

 many conversations and constant correspondence with him. I 

 conclude he based it upon the classification used by Paul Fischer 

 in his ' Manuel de Conchyliologie ' (1887), one which has to some 

 extent been adopted in the arrangement of the molluscan col- 

 lections at the Natural History branch of the British Museum. 

 With regard to the different genera Dr. Blanford had worked 

 through, the order in which some had to be placed had yet to be 

 decided ; the last morning's work we did together when he was 

 staying with me at Nore, 7th May, 1905, had reference to this 

 very point. 



I have given very considerable thought to this question of 

 classification and adopted a sequence which is as natural, I trust, 

 as our limited knowledge of the animals at the present time will 

 permit and as consonant as I can now make it with Blanford's 

 views. 



Blanford left the descriptions of three new genera, and I have 



