Smithsonian Institution. 



. 



YOL. XXXIII. 



APRIL, 1912. 



Established by BENJAMIN SIILIMAN in 1818. 



THE 



AMERICAN 



JOURNAL OF SCIENCE 



Editor: EDWARD S. DANA. 



ASSOCIATE EDITORS 



Professors GEOEGE L. GOODALE, JOHN TROWBRIDGE, 

 W. G. FARLOW and WM. 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. XXXIII-[WHOLE NUMBER, CLXXXIIL] 

 No. 196— APEIL, 1912. 



WITH PLATES I \ND II. 



NEW HAVEN, CONNECTI 



1912. 



THE TUTTLE, MOREHOUSE & TAYLOR CO., PRINTERS 



registered letter!, or bL^s S^t^Yn^?" * ^ * 



