CONTENTS 



Pages 

 North American Natural Bridges, with a Discussion of Their Origin. 



By Herdman F. Cleland .--..- 313-338 



Alaskan Earthquakes of 1 899. By Lawrence Martin - - -339-406 



Birds Hill, an Esker near Winnipeg, Manitoba. By Warren Upham. 407-432 



Relationship of Niagara River to the Glacial Period. By J. W. 



Spencer 433-440 



Relative Work of the Two Falls of Niagara. By J. W. Spencer. 441-446 



Interruption in the Flow of theTalls of Niagara in February, 1909. 



By J. W. Spencer - - - 447-448 



Geologic Work of Ants in Tropical America. By J. C. Branner. 449-496 



Internal Characters of Some Mississippian Rhynchonelliform Shells. 



By Stuart Weller 497-516 



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