ADVERTISEMENT 



The scientific publications of the National Museum include two 

 series, known, respectively, as Proceedings and Bulletins. 



The Proceedings^ begun in 1878, are intended primarily as a me- 

 dium for the publication of original papers, based on the collections 

 of the National Museum, that set forth newly acquired facts in 

 biology, anthropology, and geology, with descriptions of new forms 

 and revisions of limited groups. Copies of each paper, in pamphlet 

 form, are distributed as published to libraries and scientific organiza- 

 tions and to specialists and others interested in the different subjects. 

 The dates at which these separate papers are published are recorded 

 in the table of contents of each of the volumes. 



The Bulletins^ the first of which was issued in 1875, consist of a 

 series of separate publications comprising monographs of large 

 zoological groups and other general sj^stematic treatises (occasion- 

 ally in several volumes), faunal works, reports of expeditions, cata- 

 logues of type-specimens, special collections, and other material of a 

 similar nature. The majority of the volumes are octavo in size, but a 

 quarto size has been adopted in a few instances in which large 

 plates were regarded as indispensable. In the Bulletin series appear 

 volumes under the heading Gontrihutions from the United States 

 National Hei'haHum^ in octavo form, published by the National 

 Museum since 1902, which contain papers relating to the botanical 

 collections of the Museum. 



The present work forms No. 156 of the Bulletin series. 



Alexander Wetmore, 

 Assistant Secretary^ Smithsonian Institution. 



Washington, D. C., April, 1931. 



