﻿INVEKTEBEATES. 
  299 
  

  

  ation, 
  beyond 
  which 
  they 
  continue 
  simple 
  to 
  their 
  extremities, 
  

   making 
  four 
  arms 
  to 
  each 
  ray. 
  The 
  arm 
  joints 
  are 
  all 
  slightly 
  

   wedge-formed, 
  and 
  quite 
  short 
  above 
  the 
  second 
  division, 
  and 
  sup- 
  

   port 
  strong 
  pinnules, 
  which 
  are 
  given 
  off 
  from 
  the 
  longest 
  sides 
  of 
  

   the 
  joints. 
  

  

  The 
  anal 
  side 
  presents 
  an 
  anomalous 
  feature 
  that 
  I 
  have 
  not 
  ob- 
  

   served 
  in 
  any 
  other 
  species 
  of 
  Poteriocrinus. 
  In 
  addition 
  to 
  the 
  

   ordinary 
  anals 
  placed 
  as 
  is 
  usual 
  in 
  this 
  genus, 
  there 
  is 
  a 
  pentagonal 
  

   plate 
  about 
  as 
  long 
  as 
  the 
  radials, 
  intercalcated 
  between 
  the 
  right 
  

   posterior 
  radial 
  and 
  the 
  subradial 
  below, 
  elevating 
  the 
  lower 
  angle 
  

   of 
  this 
  radial 
  to 
  a 
  level 
  with 
  the 
  summit 
  of 
  the 
  other 
  radial 
  plates. 
  

   This 
  may 
  be 
  Only 
  an 
  abnormal 
  development, 
  and 
  I 
  was 
  at 
  first 
  in- 
  

   clined 
  to 
  regard 
  this 
  as 
  only 
  a 
  variety 
  of 
  P. 
  venustus, 
  but 
  its 
  shorter 
  

   brachials 
  and 
  arm-plates, 
  and 
  different 
  mode 
  of 
  bifurcation 
  of 
  the 
  

   arms, 
  seems 
  to 
  afford 
  good 
  grounds 
  for 
  considering 
  it 
  as 
  a 
  distinct 
  

   species. 
  

  

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

  

  No. 
  2,448, 
  Illinois 
  State 
  collection. 
  

  

  Poteeiocrinus 
  propinquus, 
  Worthen. 
  

  

  PL 
  XXIX, 
  Fig. 
  9. 
  

  

  Poteriocri'tus 
  propinquus, 
  Woethen, 
  Feb., 
  1882. 
  

  

  Bulletin 
  No. 
  1, 
  of 
  the 
  Illinois 
  State 
  Museum 
  of 
  Natural 
  History. 
  P. 
  26. 
  

  

  Body 
  below 
  medium 
  size, 
  obconic 
  or 
  bell-shaped, 
  spreading 
  rather 
  

   rapidly 
  from 
  its 
  truncated 
  base, 
  to 
  the 
  submit 
  of 
  the 
  radial 
  plates, 
  

   where 
  it 
  is 
  nearly 
  twice 
  as 
  wide 
  as 
  high. 
  

  

  Basal 
  s 
  about 
  half 
  as 
  long 
  as 
  wide 
  above 
  their 
  junction 
  with 
  the 
  

   column, 
  forming 
  a 
  shallow, 
  pentagonal 
  cup. 
  

  

  Subradials 
  on 
  the 
  anterior 
  side 
  hexagonal, 
  length 
  and 
  breadth 
  

   about 
  equal, 
  their 
  upper 
  angles 
  extending 
  up 
  about 
  half 
  the 
  length 
  

   of 
  the 
  radial 
  plates. 
  Kadials 
  one-fourth 
  to 
  one-third 
  wider 
  than 
  

   high, 
  pentagonal, 
  with 
  their 
  upper 
  margins 
  squarely 
  truncated 
  for 
  the 
  

   reception 
  of 
  the 
  brachial 
  plates. 
  

  

  Brachials 
  widest 
  at 
  their 
  lower 
  margins, 
  not 
  quite 
  as 
  long 
  as 
  wide, 
  

   constricted 
  in 
  the 
  middle, 
  and 
  sharply 
  angular 
  above, 
  where 
  they 
  

   support 
  the 
  first 
  divisions 
  of 
  the 
  rays. 
  Arms 
  four 
  to 
  eight 
  to 
  the 
  

   ray, 
  so 
  far 
  as 
  can 
  be 
  seen 
  from 
  the 
  specimen 
  under 
  examination. 
  

   The 
  left 
  posterior 
  ray 
  divides 
  the 
  second 
  time 
  on 
  the 
  eighth 
  or 
  

   ninth 
  plate 
  above 
  the 
  brachial, 
  beyond 
  which 
  the 
  arms 
  appear 
  to 
  

   be 
  simple 
  to 
  their 
  extremities. 
  The 
  right 
  antero-lateral 
  arm 
  bifur- 
  

  

  