Chas. D. Walcott, 



U. S. Geol. Survey. 

 VOL. VII. 



JUNE, 1899. 



Established by BENJAMIN SILLIMAN in 1818. 



THE 



AMERICAN 



JOURNAL OF SCIENCE. 



Editor: EDWARD S. DANA. 



ASSOCIATE EDITORS 



Professors GEO. L. GOODALE, JOHN TROWBRIDGE, 

 H. P. BOWDITCH and W. G. FARLOW, of Cambridge, 



Professors A. E. VERRILL, HENRY S. WILLIAMS, and 

 L. V. PIRSSON, of New Haven, 



Professor GEORGE F. BARKER, of Philadelphia, 

 Professor H. A. ROWLAND, of Baltimore, 

 Mr. J. S. DILLER, of Washington. 



FOURTH SERIES. 

 YOL. YII— [WHOLE NUMBER, CLVIL] 



No. 42.— JUNE, 1899. 



WITH PLATE XI. 



NEW HA YEN, CONNECTICUT. 



1899. 



TUTTLE, MOREHOUSE & TAYLOR, PRINTERS, 125 TEMPLE STREET. 



Published monthly. Six dollars per year (postage prepaid). $6.40 to 

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