﻿Jhas. 
  D. 
  Walcott, 
  

  

  U. 
  S. 
  Geol. 
  Survey. 
  

  

  VOL. 
  IX. 
  APRIL, 
  1900. 
  

  

  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 
  H. 
  A. 
  ROWLAND/ 
  of 
  Baltimore, 
  

  

  Mr. 
  J. 
  S. 
  DILLER, 
  of 
  Washington. 
  

  

  FOURTH 
  SERIES. 
  

  

  YOL. 
  IX— 
  [WHOLE 
  NUMBER, 
  CLIX.] 
  

  

  No. 
  52.— 
  APRIL, 
  1900. 
  

  

  WITH 
  PLATES 
  II-IV. 
  

  

  NEW 
  HAVEN, 
  CONNECTICUT. 
  

   19 
  00. 
  

  

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