SMITHSONIAN INSTITUTION 



UNITED STATES NATIONAL MUSEUM 



Bulletin 181 



THE CYCLOPHORID OPERCULATE 

 LAND MOLLUSKS OF AMERICA 



By 



CARLOS DE LA TORRE 

 PAUL BARTSCH 



and 



JOSEPH P. E. MORRISON 



UNITED STATES 



GOVERNMENT PRINTING OFFICE 



WASHINGTON : 1942 



For sale by the Superintendent of Documents. Washington, D. C. Price 65 cents 



