﻿INVEKTEBKATES. 
  

  

  343 
  

  

  Genus 
  ACKOCKESTUS, 
  Yandell. 
  

  

  Acrocrinus 
  Wortheni, 
  Wachsmuth. 
  

  

  PI. 
  XXX, 
  Pig. 
  13. 
  

  

  Acrocrinus 
  Wortheni, 
  Wachsmuth, 
  February, 
  1882. 
  

  

  Bulletin 
  No. 
  1, 
  of 
  the 
  Illinois 
  State 
  Museum 
  of 
  Natural 
  History, 
  p. 
  40. 
  

  

  - 
  Rocpb 
  

  

  Anal 
  plates. 
  

   Diagram 
  illustrating 
  the 
  structure 
  of 
  the 
  genus 
  Acrocrinus. 
  

  

  This 
  species 
  is 
  described 
  from 
  a 
  single 
  specimen, 
  of 
  which 
  only 
  

   the 
  calyx 
  is 
  preserved 
  ; 
  the 
  vault, 
  the 
  arms 
  and 
  the 
  columns 
  are 
  so 
  

   far 
  unknown. 
  The 
  calyx, 
  however, 
  is 
  in 
  excellent 
  preservation, 
  and, 
  

   notwithstanding 
  its 
  small 
  size, 
  exposes 
  plainly 
  every 
  plate. 
  The 
  

   form 
  is 
  calyculate, 
  broadly 
  truncate 
  at 
  the 
  bottom, 
  abruptly 
  bending 
  

   upward 
  toward 
  the 
  base 
  of 
  the 
  first 
  radials, 
  whence 
  it 
  gradually 
  

   decreases 
  in 
  width 
  to 
  the 
  arms. 
  Its 
  length 
  is 
  40.100 
  of 
  an 
  inch, 
  

   its 
  greates 
  width 
  42.100, 
  the 
  width 
  at 
  the 
  arm 
  bases 
  34.100. 
  The 
  

   plates 
  are 
  plain, 
  without 
  ornamentation, 
  but 
  sufficiently 
  convex 
  to 
  

   point 
  out 
  the 
  sutures. 
  

  

  