ADVERTISEMENT. 



The scientific publications of the United States National Museum 

 consist of two series, the Proceedings and the Bulletins. 



Tlie 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 anthro- 

 pology, 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 dates of publication are 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 (occa- 

 sionally 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 Contrihu- 

 tionsfrcm the National Herbarium, has been published as bulletins. 



The present work forms No. 100, volume 4, of the Bulletin series. 



William deC. Ravenel, 



AdminiHrative Assistant to tJie Secretary, 



in charge of the United States National Museum.. 



Washington, D. C, June, 1921. 

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