﻿INVEETEBEATES. 
  273 
  

  

  POTERIOCRINUS 
  HAMILTONENSIS, 
  Worthen. 
  

  

  PI. 
  XXVII, 
  Fig. 
  9. 
  

  

  Poteriocrinus 
  Hamiltonensis, 
  Woethbn, 
  Feb. 
  1882. 
  

  

  Bulletin 
  No. 
  1, 
  of 
  the 
  Illinois 
  State 
  Museum 
  of 
  Natural 
  History, 
  p. 
  7. 
  

  

  Body 
  short, 
  forming 
  a 
  low, 
  shallow 
  cup 
  about 
  twice 
  as 
  wide 
  as 
  

   high. 
  Base 
  concave, 
  the 
  basal 
  plates 
  being 
  hidden 
  by 
  the 
  first 
  col- 
  

   umnar 
  joints. 
  Subradials 
  of 
  nearly 
  uniform 
  size, 
  four 
  hexagonal 
  and 
  

   one 
  beptagonal, 
  all 
  curving 
  below 
  into 
  tbe 
  basal 
  concavity. 
  Eadials, 
  

   four 
  of 
  them 
  nearly 
  twice 
  as 
  wide 
  as 
  long, 
  pentagonal, 
  the 
  one 
  on 
  

   the 
  anterior 
  side 
  smaller, 
  and 
  all 
  indented 
  at 
  their 
  lower 
  angles 
  to 
  

   correspond 
  with 
  the 
  similar 
  indentations 
  of 
  the 
  upper 
  angles 
  of 
  the 
  

   subradials. 
  A 
  somewhat 
  gaping 
  suture 
  exists 
  between 
  the 
  radial 
  and 
  

   brachial 
  series. 
  Brachials, 
  one 
  to 
  each 
  ray, 
  longer 
  than 
  the 
  radials, 
  

   and 
  four 
  of 
  them 
  sharply 
  angular 
  above 
  for 
  the 
  support 
  of 
  the 
  arms. 
  

   On 
  the 
  anterior 
  ray 
  the 
  brachial 
  is 
  constricted 
  above 
  to 
  about 
  one- 
  

   half 
  its 
  width 
  below, 
  and 
  on 
  its 
  upper 
  truncated 
  margin 
  supports 
  

   the 
  plates 
  of 
  a 
  single 
  arm, 
  making 
  nine 
  arms 
  altogether 
  for 
  this 
  

   species. 
  Four 
  or 
  five 
  anal 
  plates 
  can 
  be 
  seen 
  arranged 
  as 
  usual 
  in 
  

   this 
  genus. 
  Arms 
  composed 
  of 
  short 
  quadrangular 
  plates, 
  that 
  give 
  

   off 
  strong 
  pinnules, 
  the 
  joints 
  of 
  which 
  are 
  twice 
  or 
  more 
  as 
  long 
  

   as 
  wide. 
  Column, 
  unknown. 
  

  

  This 
  species 
  is 
  nearly 
  related 
  to 
  the 
  little 
  form 
  to 
  which 
  we 
  have 
  

   given 
  the 
  name 
  P. 
  penicilliformis, 
  but 
  differs 
  from 
  that 
  in 
  its 
  more 
  

   broadly 
  cup-shaped 
  body, 
  shorter 
  brachials 
  and 
  arm-plates, 
  and 
  also 
  

   in 
  the 
  pit-like 
  depressions 
  at 
  the 
  angles 
  of 
  the 
  body-plates. 
  The 
  

   body 
  alone 
  could 
  not 
  be 
  easily 
  distinguished 
  from 
  Pot. 
  (Scaph.) 
  unicvs 
  

   of 
  Hall, 
  while 
  it 
  is 
  entirely 
  unlike 
  that 
  in 
  the 
  number 
  and 
  arrange- 
  

   ment 
  of 
  the 
  arms. 
  

  

  Geological 
  position 
  and 
  locality: 
  Upper 
  part 
  of 
  the 
  Keokuk 
  lime- 
  

   stone, 
  Hamilton, 
  Illinois. 
  

  

  No. 
  176, 
  Mr. 
  L. 
  A. 
  Cox's 
  collection. 
  . 
  

  

  Poteriocrinus 
  Orestes, 
  Worthen. 
  

  

  PI. 
  XXVII, 
  Fig. 
  3. 
  

  

  Poteriocrinus 
  Orestes, 
  Worthen. 
  Feb. 
  1882. 
  

  

  Bulletin 
  No. 
  1, 
  of 
  the 
  Illinois 
  State 
  Museum 
  of 
  Natural 
  History, 
  p. 
  7. 
  

  

  Body 
  depressed, 
  cup-shaped, 
  about 
  twice 
  as 
  wide 
  as 
  high. 
  Base 
  

   concave, 
  basals 
  small 
  and 
  concealed 
  under 
  the 
  first 
  columnar 
  joints. 
  

   Subradials 
  as 
  wide 
  or 
  a 
  little 
  wider 
  than 
  high, 
  three 
  hexagonal 
  and 
  

   two 
  on 
  the 
  posterior 
  side 
  heptagonal, 
  all 
  curving 
  into 
  the 
  cavity 
  

  

  -18 
  

  

  