D. Walcott, 



I S. Geol. Survey. 



yOL. VII. 



MAY, 1899. 



Established by BENJAMIN SILLIMAN in 1818. 



T II E 



AMERICAN 



JOURNAL OF SCIEHCE. 



Editoe: 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. 

 VOL. VII— [WHOLE NUMBER, CLVIL] 



No. 41.— MAY, 1899. 



WITH PLATES VIII-X. 



NEW HAVEN, CONNECTICUT. 

 1899. 



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



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

 foreign subscribers of countries in the Postal Union. Remittances should 

 be made either by money orders, registered letters, or bank checks. 



