34 



. 39*?) . 



I H E 



AMERICAN 



JOUBNAL OF SCIENCE. 



Established by BENJAMIN SILLIMAN in 1818. 

 EDITORS 



JAMES D. and EDWARD S. DANA. 



ASSOCIATE EDITORS 



Professors JOSIAH P. COOKE, GEORGE L. GOODALE 

 and JOHN TROWBRIDGE, of Cambridge. 



Professors H. A. NEWTON and A. E. VERRILL, of 

 New Haven, 



Professor GEORGE F. BARKER, of Philadelphia. 



THIRD SERIES. 

 YOL. XLL— [WHOLE NUMBER, CXLL] 



Nos. 241—246. 



JA35TTAKY TO JUNE, 1891. 



WITH XVIII PLATES. 





NEW HAVEN, CONN. : J. D. & E. S. DANA. 

 1891. 



