26 



The Williams Collection of Shells 



The greatest possible diversity in numbers exists 

 among these genera. Some, like Megalatractus, are 

 monotypic, while in others the specific representation 

 runs into the hundreds. Thus, under the old designa- 

 tion "Helix" are included over five hundred and fifty 

 specific names in this catalogue, while such genera as 

 Cypraea, Conus, and Mitra, are represented by three 

 or four hundred species each. The total specific 

 representation is very nearly ten thousand. 



