^ 



I). Walcott, 



U. S. Geological Survey. 



AY, I 



Established by BENJAMIN SILLIMAN in 1818. 



Til K 



AMERICAN 



JOURNAL OF SCIENCE. 



EDITORS 



JAMES D. and EDWARD S. DANA. 



I ATE EDITORS 



Professor^ 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. 



i >L. XXXIX.— [WHOLE NUMBER, CXXXIX.] 



No. 233.— MAY, 1890. 



WITH PLATES V-VII. 



NEW HAVEN, CONN. : J. D. & E. 8. DANA. 



1890. 



TUT! 



dollars per y 

 in the Postal Union. 

 : ed letters, or bank checks. 



$6.40 to foreign sub- 

 uld be made e I 



