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 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 : 

 museum catalogues : reports of explorations : aids to biblio- 

 graphical investigations, etc., generally prepared at the expressed 

 request of the Institution, and at its expense. 



The position of a work in one or the other of the two series 

 will sometimes depend upon whether the required illustrations 

 can be presented more conveniently in the quarto or the octavo 

 form. 



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 combinations into volumes. 



SPENCER F. BAIRD, 



Secretary S. I. 



(iii) 



