﻿INVEETEBEATES. 
  291 
  

  

  Brachials 
  pentagonal, 
  about 
  as 
  long 
  as 
  the 
  radials, 
  compressed 
  

   laterally, 
  so 
  as 
  to 
  form 
  a 
  rather 
  prominent 
  ridge 
  across 
  the 
  middle 
  

   of 
  the 
  plate, 
  ending 
  at 
  the 
  upper 
  angle 
  in 
  a 
  rather 
  obtuse 
  point. 
  

   All 
  the 
  body 
  plates, 
  including 
  the 
  second 
  radials, 
  are 
  marked 
  with 
  

   rugose 
  striations 
  directed 
  from 
  above 
  downward 
  to 
  the 
  base, 
  giving 
  

   a 
  rugose 
  appearance 
  to 
  the 
  surface 
  of 
  the 
  body. 
  The 
  brachials 
  are 
  

   sharply 
  angular 
  above, 
  and 
  support 
  the 
  first 
  arm 
  plates, 
  which 
  are 
  

   triangular, 
  and 
  one 
  on 
  each 
  brachial 
  is 
  produced 
  in 
  front 
  into 
  a 
  

   little 
  node 
  that 
  covers 
  the 
  projection 
  at 
  the 
  summit 
  of 
  the 
  brachial 
  

   plates. 
  The 
  succeeding 
  arm 
  plates 
  are 
  short, 
  wedge-shaped, 
  except 
  

   the 
  axillary 
  plates, 
  whicb 
  are 
  longer 
  than 
  wide, 
  and 
  produced 
  out- 
  

   wardly 
  into 
  an 
  obtuse 
  point. 
  AH 
  the 
  other 
  plates 
  of 
  the 
  arms, 
  

   where 
  well 
  preserved, 
  show 
  short 
  spiniferous 
  nodes 
  on 
  their 
  outer 
  

   margins. 
  

  

  The 
  arms, 
  after 
  their 
  first 
  division 
  on 
  the 
  brachials, 
  divide 
  again 
  

   on 
  the 
  eighth 
  or 
  tenth 
  plate, 
  and 
  the 
  outer 
  division 
  once 
  or 
  twice 
  

   more 
  on 
  the 
  sixteenth 
  to 
  the 
  twentieth 
  plate, 
  while 
  the 
  inner 
  

   branches 
  continue 
  single 
  to 
  their 
  extremities. 
  

  

  Column 
  round, 
  and 
  near 
  the 
  top 
  composed 
  of 
  short 
  plates, 
  the 
  

   alternate 
  ones 
  projecting 
  beyond 
  the 
  others. 
  

  

  Anal 
  plates 
  unknown. 
  

  

  This 
  species 
  is 
  evidently 
  related 
  to 
  the 
  crinoid 
  figured 
  by 
  Yandell 
  

   and 
  Shumard 
  in 
  their 
  ''Contributions 
  to 
  the 
  Geology 
  of 
  Kentucky," 
  

   without 
  a 
  description, 
  but 
  if 
  their 
  figure 
  is 
  correct, 
  our 
  speecis 
  

   differs 
  from 
  their 
  " 
  Gyathocrinus 
  florealis," 
  in 
  the 
  form 
  and 
  relative 
  

   proportion 
  of 
  the 
  body 
  plates, 
  as 
  well 
  as 
  in 
  the 
  bifurcations 
  of 
  the 
  

   arms. 
  

  

  Position 
  and 
  locality: 
  Chester 
  limestone 
  ; 
  Monroe 
  county, 
  111. 
  

  

  No. 
  2,436, 
  Illinois 
  State 
  collection. 
  

  

  Poteriocrinus 
  Salteei, 
  Worthen. 
  

  

  PI. 
  XXIX, 
  Fig. 
  18. 
  

  

  Poteriocrinus 
  Salteri, 
  Worthen, 
  February, 
  1882. 
  

  

  Bulletin 
  No. 
  1, 
  of 
  the 
  Illinois 
  State 
  Museum 
  of 
  Natural 
  History, 
  p. 
  21. 
  

  

  Body 
  small, 
  basin-shaped, 
  rather 
  more 
  than 
  twice 
  as 
  wide 
  as 
  high. 
  

   Base 
  depressed, 
  and 
  basal 
  plates 
  concealed 
  in 
  its 
  concavity. 
  

  

  Subradials 
  about 
  as 
  long 
  as 
  wide, 
  those 
  on 
  the 
  anterior 
  side 
  

   hexagonal, 
  the 
  lower 
  angles 
  curving 
  into 
  the 
  basal 
  depression, 
  

   protuberant 
  and 
  slightly 
  depressed 
  at 
  their 
  upper 
  angles. 
  

  

  