SMITHSONIAN INSTITUTION 



UNITED STATES NATIONAL MUSEUM 

 Bulletin 68 



A MONOGRAPH OF WEST AMERICAN 

 PYRAMIDELLID MOLLUSKS 



BY 



WILLIAM HEALEY BALL and PAUL BARTSCH 



Of the Division of Rlollusks, U. S. National Bluseiirn 



WASHINGTON 



GOVERNMENT PRINTINCi OFFICE 



1909 



