Chas. D. Walcott, 



U. S. Geological Survey. 



VOL. XXXIX. 



MAKCH, 1890. 



Established by BENJAMIN SILLIMAN in 1818. 



THE 



AMERICAN 



JOURNAL OF SCIENCE. 



EDITORS 



JAMES D. and EDWARD S. DANA. 



ASSOCIATE EDITORS 



Professors JOSIAH P. COOKE, GEORGE L. GOODALE 

 axd JOHN TROWBRIDGE, of Cambridge. 



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



New Haven, 



Professor GEORGE F. BARKER, of Philadelphia. 



THIRD SERIES. 



VOL. XXXIX.— [WHOLE NUMBER, CXXXIX.] 



No. 231.— MARCH, 1890. 



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



1890. 



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