DEDICATION. 



This Bulletin is dedicated to Mr. George H. Laflin, 

 who, interested in the advancement of science and in the 

 work of our institutions of learning, has by his generosity 

 made its publication possible. 



The Board of Managers of the Geological and Natural History 

 Survey of The Chicago Academy of Sciences : 



WILLIAM K. HIGLEY, Chairman, 

 CHARLES S. RADDIN, Secretary. 

 THOMAS C. CHAMBERLIN. 

 GAYTON A. DOUGLASS. 

 THOMAS T. JOHNSTON. 



