ADVERTISEMENT. 



The scientific publications of the National Museum consist of two 

 series— Proceedings and Bulletins. 



The Proceedings, the first volume of which was issued in 1878, are 

 intended primarily as a medium for the pubhcation of original papers 

 based on the collections of the National Museum, setting forth newly 

 acquired facts in biology, anthropology, and geology derived there- 

 from, or containing descriptions of new forms and revisions of lim- 

 ited groups. A volume is issued annually or oftener for distribution 

 to libraries and scientific estabhshments, and, in view of the impor- 

 tance of the more prominent disseminations of new facts, a limited edi- 

 tion of each paper is printed in pamphlet form in advance. The 

 dates at which these separate papers are published are recorded in 

 the table of contents of the volume. 



The present volume is the fifty-seventh of this series. 



The Bulletin, pubhcation of which was begun in 1875, is a series 

 of more elaborate papers, issued separately, and, like the Proceedings, 

 based chiefly on the collections of the National Museum. 



A quarto form of the Bulletin, known as the "Special Bulletin," 

 has been adopted in a few instances in which a larger page was 

 deemed indispensable. 



Since 1902 the volumes of the series known as ''Contributions from 

 the National Herbarium," and containing papers relating to the 

 botanical collections of the Museum, have been published as Bulletins. 



William deC. Ravenel, 

 Administrative Assistant to the Secretary, 

 in charge of the United States National Museum. 



March 20, 1921. 



