Library, U. S. Nat. Museum. 



VOL. L OCTOBER, 1920 



Established by BENJAMIN SILLIMAN in 1818. 



AMERICAN V% «o-. M. 



JOURNAL OF SCIENCE. 



Editor: EDWARD S. DANA.. 



ASSOCIATE EDITORS 



Professors GEORGE L. GOOD ALE, JOHN TROWBRIDGE, 

 and WM. M. DAYIS, 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, CC], 

 No. 298— OCTOBER, 1920. 



WITH PLATE III. 



NEW HAVEN, CONNECTICUT. 



19 20. 



THE TUTTLE, MOREHOUSE & TAYLOR CO., PRINTERS, 123 TEMPLE STREET. 



Published monthly. Six dollars per year, in advance. $6.40 to countries in the 

 Postal Union ; $6.25 to Canada. Single numbers 50 cents: No. 271, one dollar. 



Entered as second-class matter at the Post Office at New Haven, Conn., under the A ct 

 of March 3, 1879. 



