ADVERTISEMENT. 
The scientific publications of the United States National Museum consist of two 
series, the Proceedings and the Bulletins. 
The Proceedings , the first volume of which was issued in 1878, are intended 
primarily as a medium for the publication of original, and usually brief, papers 
based on the collections of the National Museum, presenting newly acquired facts in 
zoology, geology, and anthropology, including descriptions of new form's of animals 
and revisions of limited groups. One or two volumes are issued annually and dis- 
tributed to libraries and scientific organizations. A limited number of copies of 
each paper, in pamphlet form, is distributed to specialists and others interested in 
the different subjects as soon as printed. The date of publication is recorded in the 
tables of contents of the volumes. 
The Bulletins , the first of which was issued in 1875, consist of a series of 
separate publications comprising chiefly monographs of large zoological groups and 
other general systematic treatises (occasionally in several volumes), faunal works, 
reports of expeditions, and catalogues of type-specimens, special collections, etc. 
The majority of the volumes are octavos, but a quarto size has been adopted in a few 
instances in which large plates were regarded as indispensable. 
Since 1902 a series of octavo volumes containing papers relating to the botanical 
collections of the Museum, and known as the Contributions from the National Her- 
harium , has been published as bulletins, 
The present work forms No. 106 of the Bulletin series. 
William df.C. Ravenel, 
Administrative Assistant to the Secretary , 
In charge of the United States National Museum. 
Washington, I). C., April 20, 1920. 
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