﻿INVERTEBRATES. 
  285 
  

  

  differs 
  from 
  that 
  in 
  its 
  more 
  elongate 
  body, 
  the 
  very 
  thin 
  plates 
  of 
  

   which 
  it 
  is 
  composed, 
  as 
  well 
  as 
  in 
  the 
  number 
  and 
  mode 
  of 
  bifur- 
  

   cation 
  of 
  the 
  arms. 
  

  

  Position 
  and 
  locality 
  : 
  Keokuk 
  limestone, 
  Keokuk, 
  Iowa. 
  

  

  Collection 
  of 
  the 
  author. 
  

  

  Poterioceinus 
  Richfieldensis, 
  Worthen. 
  

  

  PL 
  XXX, 
  Fig. 
  5. 
  

  

  Poteriocrinus 
  Biohfieldensis, 
  Woethen, 
  Feb., 
  1882. 
  

  

  Bulletin 
  No. 
  1, 
  of 
  the 
  Illinois 
  State 
  Museum 
  of 
  Natural 
  History, 
  p. 
  15. 
  

  

  Body 
  small, 
  turbinate, 
  length 
  and 
  breadth 
  about 
  equal. 
  Basals 
  

   moderately 
  large 
  in 
  proportion 
  to 
  the 
  entire 
  body, 
  projecting 
  above 
  

   the 
  columnar 
  facet 
  so 
  as 
  to 
  form 
  a 
  shallow 
  pentagonal 
  cup. 
  

  

  Subradials 
  larger 
  than 
  the 
  basals, 
  the 
  two 
  on 
  the 
  posterior 
  side 
  

   the 
  longest, 
  and 
  hexagonal. 
  

  

  Radials 
  wider 
  than 
  long, 
  pentagonal, 
  with 
  a 
  well 
  denned 
  and 
  

   rather 
  gaping 
  suture 
  between 
  them 
  and 
  the 
  succeeding 
  brachials. 
  

   In 
  the 
  right 
  posterior 
  ray 
  the 
  brachial 
  is 
  twice 
  as 
  long 
  as 
  wide, 
  

   pentagonal, 
  supporting 
  on 
  its 
  upper 
  sloping 
  sides 
  the 
  first 
  divisions 
  

   of 
  the 
  ray. 
  In 
  the 
  left 
  posterior 
  ray 
  the 
  brachial 
  is 
  divided, 
  mak- 
  

   ing 
  two 
  brachials 
  in 
  this 
  ray, 
  the 
  first 
  quadrangular, 
  and 
  the 
  second 
  

   short 
  and 
  pentangular, 
  but 
  I 
  am 
  inclined 
  to 
  regard 
  this 
  as 
  acci- 
  

   dental, 
  and 
  to 
  believe 
  that 
  one 
  brachial 
  to 
  each 
  ray 
  is 
  the 
  normal 
  

   number. 
  

  

  The 
  first 
  anal 
  plate 
  is 
  a 
  little 
  longer 
  than 
  wide, 
  hexagonal, 
  and 
  

   rests 
  between 
  the 
  sloping 
  sides 
  of 
  the 
  two 
  posterior 
  subradials, 
  and 
  

   partly 
  under 
  the 
  left 
  side 
  of 
  the 
  right 
  posterior 
  radial. 
  The 
  second 
  

   anal 
  is 
  a 
  little 
  larger 
  than 
  the 
  first, 
  and 
  rests 
  on 
  the 
  upper 
  margin 
  

   of 
  the 
  left 
  posterior 
  subradial. 
  The 
  third 
  annal 
  is 
  smaller 
  than 
  the 
  

   others, 
  and 
  rests 
  upon 
  the 
  first. 
  

  

  Arms 
  composed 
  of 
  rounded 
  joints, 
  not 
  wedge-shaped, 
  and 
  divide 
  

   the 
  second 
  time 
  on 
  the 
  eighth 
  plate 
  above 
  the 
  brachials, 
  beyond 
  

   which 
  they 
  are 
  simple 
  in 
  the 
  posterior 
  rays, 
  the 
  only 
  ones 
  visible 
  

   in 
  our 
  specimen. 
  

  

  Column 
  round, 
  composed 
  of 
  short 
  joints, 
  and 
  rather 
  thicker 
  at 
  

   the 
  base 
  of 
  the 
  calyx 
  than 
  below. 
  

  

  Position 
  and 
  locality: 
  Shaly 
  sandstones 
  of 
  the 
  Kinderhook 
  group, 
  

   near 
  Richfield, 
  Ohio. 
  

  

  No. 
  2,474, 
  Illinois 
  State 
  collection. 
  

  

  