Cyrus A'dler, 



Librarian U. S. Nat. Museum, 



VOL. XV. APKIL, 1903. \ 



Established by BENJAMIN SILLIMAN in 1818. 

 THE 



AMERICAN 



JOURNAL OF SCIENCE. 



Editor: EDWARD S. DANA. 



ASSOCIATE EDITORS 



Professors GEO. L. GOODALE, JOHN TROWBRIDGE, 

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



Professors A. E. VERRILL, HENRY S. WILLIAMS and 

 L. V. PIRSSON, of New Haven, 



Professor GEORGE F. BARKER, of Philadelphia, 



Professor JOSEPH S. AMES, of Baltimore, 



Mr. J. S. DILLER, of Washington. 



FOURT H SERIES. 



YOL. XV— [WHOLE NUMBER, CLXV.] 



No. 88.— APRIL, 1903. 



WITH PLATES II-VIII. 



Amnion ... 

 NEW HAVEN, CONNECTICUT. 



1903 



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