The Academy op Natural Sciences of Philadelphia, 



March 11, 1921. 



I hereby certify that printed copies of the Proceedings for 1920 were 

 mailed as follows: 



Pages 1-32 June 17, 1920. 



33-64 June 18, 1920. 



65-80 June 23, 1920. 



81-135 July 12, 1920. 



" 136-198 October 6, 1920. 



" 199-214 November 4, 1920. 



" 215-278 November 20, 1920. 



" 279-293 November 23, 1920. 



" 294-340 January 7, 1921. 



" 341-388 March 3, 1921. 



" 389-402 March 11, 1921. 



WiLLiAN J. Fox, Editor 



PUBLICATION committee: 



Henry Skinner, M.D., Sc.D., Witmer Stone, A.M., Sc.D., 



Henry A, Pilsbry, Sc.D., William J. Fox, 



Milton J. Greenman, M.D. 



The President, John Cadwalader, A.M., LL.D., ex-officio. 



EDITOR: William J. Fox. 



