ADVERTISEMENT. 



The present series, entitled "Smithsonian Miscellaneous Collec- 

 tions," is intended to embrace all the publications issued directly b}- 

 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 

 investigations and researches, resulting in what are believed to be new 

 truths, and constituting positive additions to the sum of human knowl- 

 edge. 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; nmseum cata- 

 logues; 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- 

 )>ination into volumes. 



S. P. LANGLEY. 



Seci-etaiu/ S. I. 

 Ill 



