CONTENTS 



Preface 1 



Introduction 2 



Hancock Pacific Expeditions Results 5 



Key to the eastern Pacific genera and subgenera 7 



Genus Propeamussium de Gregorio 1884 9 



Propeamussium meridionale (E. A. Smith) 1885 12 



Propeamussium malpelonium (Dall) 1908 14 



Subgenus Parvamussium Sacco 1897 15 



Propeamussium (Parvamussium) alaskense (Dall) 1872 .... 18 



Propeamussium (Parvamussium) davidsoni (Dall) 1897 .... 20 



Genus Cydopecten Verrill 1897 21 



Cyclopecten benthalis sp. nov 24 



Cydopecten subhyalinus (E. A. Smith) 1885 24 



Cydopecten zephyrus sp. nov 25 



Cydopecten liriope (Dall) 1908 27 



Cydopecten bistriatus (Dall) 1916 28 



Cyclopecten catalinensis (Willett) 1931 29 



Cyclopecten cocosensis (Dall) 1908 30 



Cyclopecten acutus sp. nov 31 



Cyclopecten pernomus (Hertlein) 1935 32 



Cyclopecten exguisitus sp. nov 34 



Cyclopecten incongruus (Dall) 1916 36 



Cyclopecten barbarensis sp. nov 37 



Subgenus Delectopecten Stewart 1930 38 



Cyclopecten (Delectopecten) vancouverensis (Whiteaves) 1893 . . 40 



Cyclopecten (Delectopecten) polyleptus (Dall) 1908 43 



Cyclopecten (Delectopecten) randolphi (Dall) 1897 44 



Cyclopecten (Delectopecten) randolphi tillamookensis (Arnold) 1906 45 



Cyclopecten (Delectopecten) vitreus (Gmelin) 1791 47 



Cydopecten (Delectopecten) zacae (Hertlein) 1935 50 



Cydopecten (Delectopecten) greenlandicus (Sowerby) 1842 ... 53 



Subgenus Hyalopecten Verrill 1897 55 



Cyclopecten (Hyalopecten) neoceanicus (Dall) 1908 56 



77509 



