Chas. D. Walcott, 



U. S. Geol. Survey. 



I 



YOL. XLIY. DECEMBER, 1892. 



Established by BENJAMIN SILLIMAN in 1818. 



T H E 



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. YERRILL, of 



New Haven, 



Professor GEORGE E. BARKER, of Philadelphia. 



THIRD SERIES. 



YOL. XLIY.— [WHOLE NUMBER, CXLIY.] 



No. 264— DECEMBER, 1892. 



WITH PLATES IX-X. 



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

 1892.- 



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



Published mouilily. Six dollars per year (postage prepaid). $6.40 to foreign sub- 

 scribers of countries in the Postal Union. Remittances should be made either by 

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