SMITHSONIAN INSTITUTION 



UNITED STATES NATIONAL MUSEUM 



Bulletin 68 



A MONOGRAPH OF WEST AMERICAN 

 PYRAMIDELLID MOLLUSKS 



BY 



WILLIAM HEALEY DALL and PAUL BARTSCH 



Of the Division of Mollitsks, U. S. National Museum 





.s 





WASHINGTON 



GOVERNMENT PRINTING OFFICE 



1909 



