i8o C O N C H O L O G Y. 



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SECTION X. 



ART IV. turbinated or fpiral Uni- 

 valves. 



The turbinated Shells, properly fo called, 

 are thofe Shells whofe fpires are external, 

 and (hew themfelves on the outer part of 

 the Shell in what is called the clavicle or 

 turban (clavicula) which is either produced 

 fhort or flat, according to the feveral genera 

 or Ipecies. 



It is this fourth part, or turbinated Uni- 

 valves, which is the moft difficult to ar- 

 range, and in which authors, in their dif- 

 ferent fyflems, have difplayed their different 

 opinions. No wonder ! fince it not only 

 contains myriads of fpecies more than all 

 the other three parts put together ; but 

 befides, the chara6lers of them are fraught 



5 with 



