PREFACE TO THE THIRD EDITION. 



IN bringing out this new edition of my little- book on shells, I 

 must thank my friend, Mr. J. W. Taylor, F.L.S., for having kindly 

 revised the systematic part and for having brought the very valuable 

 " Census " up to date. 



The text of Chapters I. -III. has not been altered except to make 

 what corrections I considered necessary. In Chapter IV. three 

 species new to the British fauna have been described Arion 

 minimus, Paludestrina jenkinsi, and Physa heterostropha. The 

 genus Hydrobia of the former editions has, in accordance with 

 the law of priority, been re-named as Paludestrina, Paludina as 

 Vivipara, Dreissena as Dreissensia,Bulimus as Buliminus, Achatina 

 as Cacilioides, and Acme as Acicula. For the same reason 

 Sphcertum ovale has been re-christened as S. palliditm, Pisidium 

 roseum as P. milium, Planorbis lineatus as Segmentina nitida, P. 

 nitidus as P. fontanus, P. complanatus as P. umbilicalus, Physa 

 hypnorum as Bullinus hypnoruni, Limn&a glutinosa as Amphi- 

 peplea glutinosa, Ancylus lacustris as Velletia lacustris, Limax 

 agrestis as Agriolimax agrestis, L. Icevis as Agriolimax lavis, L. 

 arborum as L. marginatus, Amalia marginata as A. sowerbyi, 

 Hyalinia Draparnaldi as H. ludda, H. glabra as H. helvetica, 

 Helix sericea as H. granulata, H. ericetornm as H. itala, Pupa 

 ringens as P. anglica, P. umbilicata as P. cylindracea, P. 

 marginata as P. muscorum, Clausilia rugosa as C. bidentata, and 

 Cochlicopa tridens as Azeca tridens. 



I may take this opportunity of once more drawing the attention 

 of workers in conchology to the importance of knowing the structure 



