

U 



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, 

 Mr. J. S. DILLER, of Washington. 



FOURTH SERIES. 

 VOL. XI— [WHOLE NUMBER, CLXL] 



WITH SEVEN PLATES. 



NEW HAVEN, CONNECTICUT^ ~. rt> 



i90i. /ftsjr 



