Chas. D. Walcott, 



XJ. S. Geological Survey. 



VOL. XXXVIII. DECEMBER, 1889. 



Established by BENJAMIN SILLIMAN in 1818. 



THE aRWALCorPr 

 AMERICAN 



JOURNAL OF SCIENCE. 



EDITOES 



JAMJES D. and EDWARD S. DANA. 



ASSOCIATE EDITOES 



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. 



VOL. XXXVIII.— [WHOLE NUMBER, CXXXVIIL] 



No. 228.— DECEMBER, 1889. 



WITH PLATES XI-XIII. 



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

 1889. . 



TLTTTLE, MOREHOUSE & TATLOR, PRINTERS, 371 STATE STREET 



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

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