ADVERTISEMENT. 



The extension of tlie scope of the National Museum during recent 

 years and the activity of the collectors employed ill its interest have 

 caused a great increase in the amount of material in its possession. 

 Many of the objects gathered are of a novel and important character, 

 and serve to throw a new light upon the study of nature and of man. 



The importance to science of promj^t publication of descriptions of 

 this material led to the establishment, in 1878, of the present series 

 of publications, entitled " Proceedings of the United States National 

 Museum," the distinguishing peculiarity of which is that the articles 

 are published in pamphlet form as fast as completed and in advance of 

 the bound volume. The present volume constitutes the twenty-first 

 of the series. 



The articles in this series consist: First, of papers prepared by the 

 scientific corps of the National Museum; secondly, of papers by others, 

 founded upon the collections in the National Museum; and, finally, 

 of facts and memoranda from the corresi)ondence of the Smithsonian 

 Institution. 



The Bulletin of the National Museum, the publication of which was 

 commenced in 1875, consists of elaborate papers based upon the collec- 

 tions of the Museum, reports of expeditious, etc., while the Proceedings 

 facilitate the prompt i)ublication of freshly acquired facts relating to 

 biology, anthropology, and geology, descriptions of restricted groups 

 of animals and j)lants, the discussion of particular questions relative 

 to the synonomy of species, and the diaries of minor expeditions. 



Other papers of more general popular interest are printed in the 

 Appendix to the Annual Eeport. 



Papers intended for publication in the Proceedings and Bulletin of 

 the National Museum are referred to the Advisory Committee on Pub- 

 lications, composed as follows: Frederick W. True (chairman), Marcus 

 Benjamin (editor), James E. Benedict, Otis T. Mason, Leouhard 

 Stejueger, and Lester F. Ward. 



S. P. Langlet, 

 Secretary of the Smithsonian Institution. 



