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 CHAP. XXXVI. 



UNIVALVES. 

 DENTALIUM ; Tooth, or Tusk Shell. 



Q. WILL you have the goodness to describe 

 the Dentalium ? 



A. The shell is strait, or nearly so, tubular 

 (or like a tube), open at both ends. 



Q. Is not the construction of the shell ex- 

 tremely simple ? 



A. Yes : they are all, more or less, as their 

 name implies, like teeth or tusks, and are com- 

 pletely separated from the other tubular families 

 by being entirely without any contortion, though 

 somewhat curved. 



CHAP. XXXVII. 



UNIVALVES: 

 SERPULA ; Worm Shell. 



Q. WHAT kind of shell is the Serpula? 



A. Linnaeus defines it to be of a tubular form, 

 gradually tapering, and generally adhering to 

 other substances. To which we may add, that 

 the end, and occasionally the whole shell, is 

 twisted into a spiral form ; which creeping and 

 F 3 



