PREFACE 5 



The chapter on Fresh Water Mollusks was written by 

 ]\Ir. Harold Hannibal, who is an earnest student in that 

 interesting field of research ; and his conclusions, while 

 somewhat opposed to past usage, have been adopted by 

 him after much investigation. 



Especial acknowledgments are due to the authorities 

 of the United States National Museum for permission 

 to copy figures found in their bulletins. This permission 

 has been freely used, as the large number of illustrations 

 marked with an asterisk (*) will testify. Thanks are 

 also due to Dr. William H. Dall for helpful suggestions, 

 to Mr. and Mrs. T. S. Oldroyd for assistance in various 

 ways, to Professor William J. Raymond of the Uni- 

 versity of California for help in the study of the Chitons, 

 and to the manv friends who have encourao'ed the writer 

 to put forth a substitute for the burned book. Thanks 

 are due also to the publishers, the Whitaker & Ray- 

 Wiggin Company, for their patience, for their assistance 

 in preparing suitable colored illustrations, and for put- 

 ting the work into so presentable a form. 



In conclusion, I would express my growing appreci- 

 ation 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 

 complete knowledge of West Coast Shells. 



TosiAii Keep. 



Mills College, California, 

 November 75, ipio. 



