﻿INVERTEBRATES. 
  297 
  

  

  Base 
  truncated, 
  the 
  basal 
  plates 
  extending 
  above 
  and 
  beyond 
  the 
  

   columnar 
  facet, 
  so 
  as 
  to 
  form 
  a 
  low 
  pentagonal 
  cup. 
  Subradials 
  

   about 
  as 
  long 
  as 
  wide, 
  three 
  of 
  them 
  hexagonal, 
  and 
  two 
  on 
  the 
  pos- 
  

   terior 
  side 
  larger 
  than 
  the 
  others 
  and 
  heptagonal. 
  

  

  Badials 
  nearly 
  or 
  quite 
  twice 
  as 
  wide 
  as 
  long, 
  pentagonal, 
  and 
  

   truncated 
  squarely 
  across 
  the 
  entire 
  length 
  of 
  their 
  upper 
  margins 
  

   for 
  the 
  reception 
  of 
  the 
  brachial 
  plates. 
  

  

  Brachials 
  one 
  to 
  the 
  ray 
  on 
  the 
  two 
  rays 
  visible, 
  about 
  the 
  same 
  

   size 
  as 
  the 
  radials, 
  supporting 
  on 
  their 
  upper 
  sloping 
  sides 
  the 
  first 
  

   divisions 
  of 
  the 
  rays. 
  

  

  The 
  arms 
  are 
  composed 
  throughout 
  of 
  short, 
  wide, 
  quadrangular 
  

   plates, 
  and 
  after 
  the 
  first 
  division 
  on 
  the 
  radials, 
  divide 
  again 
  in 
  the 
  

   left 
  posterior 
  ray 
  on 
  the 
  ninth 
  or 
  tenth 
  plates 
  and 
  on 
  the 
  right 
  

   antero-lateral, 
  on 
  the 
  seventh 
  and 
  eleventh 
  plate, 
  beyond 
  which 
  

   they 
  are 
  simple 
  as 
  far 
  as 
  can 
  be 
  seen, 
  making 
  four 
  arms 
  to 
  each 
  

   of 
  these 
  rays. 
  

  

  The 
  anal 
  side 
  of 
  the 
  specimen 
  is 
  distorted, 
  but 
  six 
  small 
  anal 
  plates 
  

   are 
  partially 
  exposed, 
  arranged 
  in 
  two 
  rows. 
  

  

  This 
  species 
  is 
  related 
  to 
  Pot. 
  (Scaph.) 
  Randolphensis 
  from 
  the 
  

   same 
  horizon, 
  but 
  differs 
  essentially 
  from 
  that, 
  in 
  the 
  mode 
  of 
  bifur- 
  

   cation, 
  and 
  the 
  wide, 
  short 
  plates 
  of 
  the 
  arms. 
  

  

  Position 
  and 
  locality.- 
  Chester 
  limestone, 
  bluffs 
  of 
  the 
  Okaw 
  river 
  

   above 
  Chester, 
  Bandolph 
  county, 
  111. 
  

  

  No. 
  2,441, 
  Illinois 
  State 
  collection. 
  

  

  Poteriocbinus 
  venustus, 
  Worthen. 
  

  

  PI. 
  XXIX, 
  Fig. 
  13. 
  

  

  Poteriocrinus 
  venustus, 
  Wokthen, 
  February, 
  1882. 
  

  

  Bulletin 
  No. 
  1, 
  of 
  the 
  Illinois 
  State 
  Museum 
  of 
  Natural 
  History, 
  p. 
  24. 
  

  

  Body 
  small, 
  obconical, 
  gradually 
  swelling 
  from 
  the 
  base 
  to 
  the 
  top 
  

   of 
  the 
  radial 
  plates, 
  where 
  it 
  is 
  about 
  once 
  and 
  a 
  half 
  as 
  wide 
  as 
  

   long. 
  

  

  Basals 
  extending 
  about 
  half 
  their 
  length 
  above 
  the 
  first 
  columnar 
  

   joints, 
  forming 
  a 
  low 
  pentagonal 
  cup. 
  

  

  Subradials 
  nearly 
  equal 
  in 
  size, 
  three 
  hexagonal, 
  and 
  two 
  on 
  the 
  

   posterior 
  side 
  heptagonal. 
  

  

  Badials 
  four, 
  a 
  little 
  wider 
  than 
  long, 
  the 
  right 
  posterior 
  one 
  

   rather 
  narrower 
  than 
  the 
  others, 
  and 
  all 
  pentagonal. 
  

  

  