IV PllEFACE. 



known only as yet by their shell, so many characteristic 

 generic forms have been described, that the nature of nearly 

 all may be fairly determined by analogy. 



The species selected for illustration in the present work 

 are represented as they appear alive. It would not be 

 possible to form a cabinet collection of them in this state, 

 for even when preserved in spirits the soft or mollus- 

 cous portion becomes, in a measure, contracted and dis- 

 coloured : but the shells or hard parts are readily collected, 

 and it is hoped that the following popular account of the 

 instincts and habits of the constructing animals will render 

 their shells more intelligible and of greater iiiterest. 



