PREFATORY NOTE 



The six Memoirs included in this vohime appeared at various dates as follows: 

 Memoir No. 1, December, 1915; 

 No. 2, November, 1916; 

 No. 3, November, 1916; 

 " No. 4, April, 1917; 



No. 5, September, 1918; 

 No. 6, July, 1920. 



Owing to circumstances beyond the control of the Director and Editor of the 

 publications of the Carnegie Museum a partial suspension of the publishing activi- 

 ties of the Museum took place during the period in which the United States of 

 North America were at war with the so-called "Central Powers" of Europe. 

 This cessation of our issue of scientific literature was only temporary. At the time 

 these lines are being written a resumption of our activities along the lines alluded 

 to has taken place. The issue of Memoir No. 6 from the pen of Mr. 0. A. Peterson 

 upon "The American Diceratheres " concludes the Seventh Volume of the Memoirs. 

 The Eighth Volume of the Memoirs is well under way, Memoir No. 1 having already 

 appeared and No. 2 being in the hands of the printers. The publication of the 



"Annals" has also been resumed. 



W. J. Holland. 



Carnegie Museum, 

 July, 1920. 



in 



