vm PREFACE 



new ones which have turned up in the course of the work. It is hoped that 

 another part will conclude this series of papers, and comprise, besides the 

 remaining descriptions, a summary of the faunal population of each of the 

 principal Neocene horizons. 



To Dr. Charles D. Walcott, Director of the United States Geological 

 Survey, to the authorities of the Smithsonian Institution and National 

 Museum, and to numerous private correspondents and colleagues, thanks are 

 due for facilities accorded and assistance rendered in the prosecution of the 

 work. 



William Healey Dall. 



