INTRODUCTION. XXXIX 



This operation must be managed by first plunging 

 them into boiling water, and, afterwards, carefully 

 picking them out, so as (if possible) not to break the 

 spiral part, or leave a portion behind. When this 

 cannot be avoided, the shell should be left in cold 

 water, till the part decays, when it may be washed 

 out. In Bivalves, and other shells, the fish may 

 be easily removed with a knife. After which, a string 

 should be tied round the valves, across the shell, to 

 keep it close till the cartilage at the hinge stiffens. 



As shells are of a calcareous nature, it follows 

 that all acids must be more or less injurious, that 

 are made use of to clean them. Many shells are 

 fished up so clean and perfectly polished by Nature, 

 that they require no assistance from art. Others, 

 on the contrary, come out of the sea slimy, and 

 covered with extraneous substances, such as coral- 

 lines, fuci, &c. These must be cleaned with soap 

 and water, and a hard tooth-brush, which is best 

 adapted of any thing I know for the purpose. The 

 extraneous coralline substances that remain on the 

 surface of the shell, after it has been cleaned, may 

 be removed with muriatic acid, diluted- with three 

 parts of water, being careful, at the same time, not 

 to touch the shell with the acid. 



Many shells have an outer skin, called an epi- 

 dermis ; this sometimes adheres very strongly, and, 

 although scientific collectors choose to have their 



