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 

 constituting the " Smithsonian Contributions to Knowledge." The 

 quarto series includes memoirs, embracing the records of extended 

 original investigations and researches, resulting in what are be- 

 lieved to be new truths, aud constituting positive additions to the 

 sum of human knowledge. The octavo series is designed to con- 

 tain 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 ex- 

 plorations ; aids to bibliographical investigations, etc., geuex'ally pre- 

 pared at the express request of the Institution, and at its expense. 



The assignment of a work to 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 voluiue in which it is placed. In many 

 cases works have been published, and largely distributed, years 

 before their combination into volumes. 



S. P. L ANGLE Y, 



Secretary S. J. 



[3] 



