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knowledgments to those who have assisted me in various 
ways. Information found in volumes of “The Nautilus,” 
“The Manual of Conchology,” and other scientific books, 
has been freely used, and especially that contained in the 
“Bulletins of the United States National Museum.” 
Especial acknowledgments are due to the authorities of 
the latter institution, for permission to copy engravings 
of shells —a permission which has been freely used. 
The number placed under each one of such engravings 
is followed by an asterisk (*), to denote its origin. 
The “Catalogue of Shells,” by the late Dr. J. G. Cooper, 
should also be mentioned, as helpful for deciding localities. 
Sincere thanks are returned to Dr. William H. Dall 
and his co-laborers in the Smithsonian Institution for 
many helpful suggestions; to Professor William J. Ray- 
mond, of the University of California, for the list of 
Chitons, and for other assistance; to Mr. and Mrs. T. S. 
Oldroyd, of Long Beach, Cal., for the opportunity to 
examine their remarkable collection of shells; to Ralph 
Arnold, Ph. D., of Stanford University, for assistance 
derived from his recent valuable publication on the fossil 
Shells of San Pedro; also to Dr: R. E. C. Stearns, Rev. 
E. H. Ashmun, Mr. Henry Hemphill, and many others, 
who in various ways have given encouragement and 
assistance. 
In conclusion, I would express my growing apprecia- 
tion of the magnitude of the field which I have attempted 
to cover, and my hope that this work may be accepted by 
students as a helpful assistance towards obtaining a com- 
plete knowledge of West American Shells. 
JostAH KEEP. 
Mills College, California, 
July II, 1904. 
