

VOL. L JULY, 1920 



Established by BENJAMIN SILLIMAN in 1818. 



JUL 1 3 1920 



AMERICA^ 



JOURNAL OF SCIENCE. 



Editor: EDWARD S. DANA. 



ASSOCIATE EDITORS 



Professors GEORGE L. GOODALE, JOHN" TROWBRIDGE, 

 and WM. M. DAVIS, of Cambridge, 



Professors A. E. VERRILL, HORACE L. WELLS, CHARLES 



SCHUCHERT, H. E. GREGORY, and HORACE S. 



UHLER, of New Haven, 



Professor JOSEPH S. AMES, of Baltimore, 

 Mr. J. S. DILLER, of Washington. 



FOURTH SERIES 

 VOL. L— [WHOLE NUMBER, CO]. 

 No. 295— JULY, 1920. 



NEW HAVEN, CONNECTICUT. 



19 20. 



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