(Jhas. L>. Walcott, 



U. S. Geological Survey. 



JNO. gU8. VOL. IIIV. * APRIL, 1888. 



Established by BENJAMIN SILLIMAN in 1818. 



THE 



AMERICAN 



JOURNAL OF SCIENCE. 



EDITORS 



JAMES D. and EDWARD S. DANA. 



ASSOCIATE EDITORS 



Professors JOSIAH P. COOKE, GEORGE L. GOODALE 

 and JOHN TROWBRIDGE, op Cambridge, 



Professors H. A. NEWTON and A. E. VERRILL, of 



New Haven, 



Professor GEORGE F. BARKER, of Philadelphia. 



THIRD SERIES. 



VOL. XXXV. -[WHOLE NUMBER, OXXXVJ 

 No. 208— APRIL, 1888. 



WITH PLATES III, IV, Y. 



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



1888. 



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