gririxation. 



TO JOHN EDWARD GRAY, Ph.D., F.R.S. 



Dear Dr. Gray, 



It is forty-two years since you published, as a student, 

 in the ' London Medical Expository,' your first memoir on some of 

 our Land and Freshwater Mollusks. Ten years later, you were 

 good enough to encourage me, as a youth, in the pursuit of our 

 favourite science, and I enjoyed many pleasant days over your 

 collection of shells in the society of yourself and Mrs. Gray. 



Another ten years passed, and I had the honour of reading, at a 

 meeting of the Academy of Sciences of Paris, my first crude 

 notions of a ' System of Conchology.' The volumes in which 

 they were embodied, published by Messrs. Longman and Co., in 

 1841, were costly, and the only chance left to me of pursuing 

 the subject was to turn printer and publisher myself. With a 

 lithographic press, a staff of print- colourers, a stock of types, 

 and a printing-press, the means of production became compara- 

 tively easy. During the twenty-two years elapsed since, I have 

 worked unremittingly on species, considering them more with re- 

 ference to the phenomena of distribution than of classification. 

 My ' Conchologia Iconica' has reached its fourteenth volume, and 

 eighteen-hundredth plate. 



Impressed with the feeling that it would be useful to show 

 how our British molluscan fauna is represented in other parts of 

 the globe, I have commenced an attempt to bring this experience 

 to bear on the subject. Our opinions on what constitutes a genus 



