Chas. .D. Walcott, 
U. S. Geological Survey. 
Be 
ert awein ek LT ja _ MAY, 1887. 
Established by BENJAMIN SILLIMAN in 1818. 
OD. VW 2OTT 
: AMERICAN 
| JOURNAL OF SCIENCE 
EDITORS 
JAMES D. anv EDWARD S. DANA. 
: ASSOCIATE EDITORS 
Prorgssors ASA GRAY, JOSIAH P. COOKE, anp 
_ JOHN TROWBRIDGE, or Camsrines, 
Prorrssors H. A. NEWTON anp A. E, VERRILL, or 
New Haven, 
PRoFEssor GEORGE F. BARKER, or Patwapereura. 
THIRD SERIES, 
VOL. XXXIII.—[WHOLE NUMBER, CXXXIIL] 
No. 197—MAY. 1887. 
Be WITH PLATE XI. 
NEW HAVEN, CONN: J. D. & ES. DANA. 
1887. 
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