

ADVERTISEMENT. 



The present series, entitled " Smithsonian Miscellaneous Collec- 

 tions," is intended to embrace all the publications issued directly by 

 the Smithsonian Institution in octavo form ; those in quarto constitut- 

 ing the " Smithsonian Contributions to Knowledge." The quarto series 

 includes memoirs, embracing the records of extended original investi- 

 gations 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 col- 

 lecting 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 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 com- 

 bination into volumes. 



S. P. LANGLEY, 



Secretary S. I. 



(iii) 



