PREFACE. xl 



long ago foresaw that photography was destined, at 

 no distant period, to hold a foremost rank among the 

 means employed for book illustration. Of late years 

 several processes have been discovered by which im- 

 pressions, of absolute permanency, from photographic 

 negatives can be printed in ink of almost any colour. 

 My first intention was to have photographed the 

 shells myself, and to have had impressions taken 

 from the negatives by the " Albertype " process, but 

 finding, on inquiry at the office of the company to 

 which the patent right of that process belongs, that 

 no saving of expense would be effected by my doing 

 so, I abandoned the idea. Photographs of the natural 

 size were therefore, in my presence, taken of all the 

 shells at the company's establishment at Baling, 

 and the prints were afterwards produced by their 

 " Albertype " process. 



As it would be very difficult, if not impossible, to 

 induce slugs to "sit for their portraits," the attempt 

 to do so was not made; they have therefore been 

 illustrated by lithographs from drawings copied from 

 other works, principally from that by Moquin-Tandon, 

 entitled ' Histoire Naturelle des Mollusques terrestres 

 et fluviatiles de France/ to which admirable book I 

 am also indebted for the descriptions (of which I have 

 made abbreviated translations) of the animals or soft 

 parts of many of our land and fresh-water molluscs. 

 The figure of Testacella Haliotidea, however, is from 

 a drawing made by Mr. Foord of a living speci- 

 men in my possession, which obligingly sat for its 

 likeness. 



