ADVERTISEMENT. 



The present series, entitled " Smithsonian Miscellaneous Col- 

 lections," is intended to embrace all the publications issued 

 directly by the Smithsonian Institution in octavo form ; those 

 in quarto constituting the "Smithsonian Contributions to 

 Knowledge." The quarto series includes memoirs, embracing 

 the records of extended original investigations and researches, 

 resulting in what are believed to be new truths, and constituting 

 positive additions to the sum of human knowledge. The octavo 

 series is designed to contain reports on the present state of our 

 knowledge of particular branches of science ; instructions for 

 collecting and digesting facts and materials for research ; lists 

 and synopses of species of the organic and inorganic world ; 

 museum catalogues ; reports of explorations ; aids to biblio- 

 graphical investigations, etc., generally prepared at the express 

 request of the Institution, and at its expense. 



In the Smithsonian Contributions to Knowledge, as well as in 

 the present series, each article is separately paged and indexed, 

 and the actual date of its publication is that given on its special 

 title-page, and not that of the volume in which it is placed. In 

 many cases works have been published and largely distributed, 

 years before their combination into volumes. 



S. P. LANGLEY, 



Secretary S. I. 



(iii) 



