ADVERTISEMENT. 
The extension of the scope of the National Museum dumrng the past 
few years, and the activity of the collectors sent out in its interests, 
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 prompt 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 Mu- 
seum,” the distinguishing peculiarity of which is that the articles are 
published in signatures as soon as matter sufficient to fill sixteen pages 
has been obtained and printed. The date of publication being plainly 
expressed in each signature, the ready settlement of questions of priority 
is assured. 
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 
interesting facts and memoranda from the correspondence of the Smith- 
sonian Institution. 
The Bulletins of the National Museum, the publication of which was 
commenced in 1875, consist of elaborate papers (monographs of families 
of animals, &c.), while the present series contemplates the prompt pub- 
lication of freshly acquired facts relating to biology, anthropology, and 
geology; descriptions of restricted groups of animals and plants; the 
settlement of particular questions relative to the synonymy of species, 
and the diaries of minor expeditions. 
This series of publications was commenced in 1878, with volume I, 
under the title ‘“‘ Proceedings of the United States National Museum,” 
by the authority and at the expense of the Interior Department, and 
under the direction of the Smithsonian Institution. 
The present volume, constituting the sixth of the series, has been pre- 
pared under the editorial supervision of Dr. Tarleton H. Bean, curator 
of the department of fishes. 
SPENCER F. BAIRD, 
Director of the U. S. National Museum. 
UNITED STATES NATIONAL MUSEUM, 
Washington, June 9, 1884. 
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