Chas. D. Walcott, 



U. S. Geological Survey. 



V r OL. XXXIX. 



JUNE, 1890. 



Established by BENJAMIN SILLIMAN in 1818. 



C.D.WALCOTZ 



THE 



AMERICAN- 

 JOURNAL OF SCIENCE. 



EDITORS 



JAMES D. and EDWARD S. DANA. 



ASSOCIATE EDITORS 



Professors JOSIAH P. COOKE, GEORGE L. GOODALE 

 and JOHN TROWBRIDGE, of Cambridge. 



Professors H. A. NEWTON and A. E. VERRILL, of 



New Haven, 



Professor GEORGE F. BARKER, of Philadelphia. 



THIRD SERIES. 



YOL. XXXIX.— [WHOLE NUMBER, CXXXIX.] 

 No. 234.— JUNE, 1890. 



WITH ONE PLATE. 



NEW HAVEN, CONN. : J. D & E. S. DANA. 



1890. 



TUTTLE, MOREHOUSE & TAYLOR, PRINTERS. 371 STATE STREET. 



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