ADVEETISEMENT. 



The jjresent series, entitled " Smithsonian Miscellaneous Col- 

 lections," is intended to embrace all the publications issued di- 

 rectly by the Smithsonian Institution in octavo form ; those in 

 quarto constituting the " Smithsonian Contributions to Knowl- 

 edge." The quarto series includes memoirs, embracing the 

 records of extended original investigations and researches, re- 

 sulting 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 ; mu- 

 seum catalogues ; reports of explorations ; aids to bibliographical 

 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) 



