PREFACE 



Since 1931 the Allan Hancock Pacific expeditions have been con- 

 cerned with the marine fauna of the west coasts of North and South 

 America, collecting from Oregon to Peru and the Galapagos Islands. 

 Among the many results of scientific importance is an extremely large 

 assemblage of m.olluscan material, undoubtedly the most comprehensive 

 in existence from the area. 



The author immediately consented when Dr. Norman T. Mattox, of 

 the Hancock Foundation, asked him to identify the many specimens of 

 Pectinidae in the Foundation collection, for the opportunity to study 

 such a wealth of regional material was both welcome and valuable to 

 one especially interested in that family. After the identifications were 

 completed, Dr. Mattox suggested the preparation of a report on the 

 material. Since twenty-six of the fortj^-eight previously described eastern 

 Pacific species were represented, as well as seven new species, the author 

 recommended enlarging the scope of the paper so as to present a sys- 

 tematic study of the entire fauna. As in any undertaking of this kind, 

 the assistance of other workers was needed ; the author was fortunate in 

 having the cooperation of those mentioned below. 



Of the Foundation staff, Dr. John S. Garth, Dr. Olga Hartman 

 and Dr. Mattox assisted in various ways. Mrs. Dorothy M. Halmos, 

 the librarian, and her assistant. Miss Mary Ellen Pippin, were most 

 helpful throughout the preparation of the paper, for the remarkably 

 extensive Foundation library filled the majority of the author's needs in 

 reference material. Mrs. Halmos also verified many of the references 

 appearing in the paper, edited the paper, and contributed valuable sug- 

 gestions. 



Dr. Harald A. Rehder, of the U. S. National Museum, compared 

 specimens of several of the new species with the holotypes of related 

 species, loaned specimens from the type-lots of two species, supplied 

 photographs of five species (two of which had never been figured), and 

 sent the author 139 lots of material from the Museum collection for 

 identification. Dr. A. Myra Keen, of Stanford University, provided 

 important data, photographs of Pecten magnificus Sowerby and Pecten 

 (Leptopecten) euterpes Berry, and permitted the author to examine the 

 Stanford collection. Dr. E. L. Bousfield, of the National Museum of 

 Canada, loaned type-lot specimens of Pecten andersoni Dall. Dr. Vicente 

 Conde, of the Redpath Museum, McGill University, Montreal, supplied 



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