

ALLAN HANCOCK PACIFIC EXPEDITIONS 



VOLUME 20 



NUMBER 1 



A REPORT ON THE FAMILY MYTILIDAE 



(Pelecypoda) 



(Plates 1-10; Text-figures 1-78) 



BY 



TRON SOOT-RYEN 



CEUEB 



THE UNIVERSITY OF SOUTHERN CALIFORNIA PRESS 



LOS ANGELES, CALIFORNIA 



1955 



