

Xs3 



THE 



AMERICAN 



JOURNAL OF SCIENCE 



Editor: EDWAKD S. DANA. 



ASSOCIATE EDITORS 



Professors GEORGE L. GOODALE, JOHN TROWBRIDGE, 

 W. G. FARLOW and WI. M. DAVIS, of Cambridge, 



Professors ADDISON E. VERRILL, HORACE L. WELLS, 



LOUIS V. PIRSSON, HERBERT E. GREGORY 



and HORACE S. UHLER, of New Haven, 



Professor HENRY S. WILLIAMS, of Ithaca, 



Professor JOSEPH S. AMES, of Baltimore, 



Mr. J. S. DILLER, of Washington. 



FOURTH SERIES 



VOL. XXXIX— [WHOLE NUMBER, CLXXXIXJ. 



WITH NINE PLATES. 



NEW HAVEN, CONNECTICUT. 



1 915. 



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