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 Mu <eum, presenting newly acquired facts in 

 zoology, geology, and anthropology, including descriptions of new forms 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 catalogue's oi' 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 Xutionul Her- 

 barium, has been published as bulletins. 



The present work forms No. 106 of the Bulletin series. 



WILLIAM DEC. RAVENEL, 

 Administrative Assistant to the Secretary, 

 I n charge of the Unitnl -SY./A \ \ntional Museum. 



WASHINGTON, D. C., April 20, 1920. 



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