﻿INVEKTEBBATES. 
  315 
  

  

  openings 
  and 
  the 
  central 
  spine 
  on 
  two 
  of 
  the 
  rays. 
  Arm 
  openings 
  

  

  two 
  to 
  each 
  ray. 
  Arms 
  and 
  column 
  unknown. 
  

  

  This 
  species 
  is 
  related 
  to 
  T. 
  sexlobatus, 
  (Shumard's 
  sp.) 
  but 
  differs 
  

  

  from 
  that 
  in 
  its 
  more 
  symmetrical 
  form, 
  its 
  less 
  protuberant 
  radial 
  

  

  and 
  anal 
  plates, 
  and 
  less 
  nodose 
  summit. 
  

   Position 
  and 
  locality 
  : 
  Chester, 
  limestone, 
  Monroe 
  county, 
  Illinois- 
  

   No. 
  2,453, 
  Illinois 
  State 
  collection. 
  

  

  Genus 
  AGASSIZOCKLNTJS, 
  Troost. 
  

   Agassizocrinus 
  papillatus, 
  Worthen. 
  

  

  PL 
  XXIX, 
  Pig. 
  17. 
  

   Agassizocrinus 
  papillatus, 
  Wokthen, 
  Feb., 
  1882. 
  

   Bulletin 
  No. 
  1, 
  of 
  the 
  Illinois 
  State 
  Museum 
  of 
  Natural 
  History, 
  p. 
  36. 
  

  

  Body 
  rather 
  below 
  the 
  medium 
  size, 
  subovate, 
  width 
  at 
  the 
  sum- 
  

   mit 
  of 
  the 
  radials 
  a 
  little 
  more 
  than 
  the 
  length, 
  composed 
  of 
  mas- 
  

   sive, 
  slightly 
  rounded 
  plates 
  that 
  are 
  separated 
  by 
  well-defined 
  and 
  

   deep 
  sutures. 
  

  

  Basals 
  pentangular, 
  about 
  as 
  wide 
  as 
  long, 
  and 
  rounded 
  below, 
  

   where 
  their 
  inner 
  margins 
  form 
  the 
  walls 
  of 
  a 
  very 
  small 
  pentapet- 
  

   alous 
  opening 
  for 
  the 
  attachment 
  of 
  a 
  very 
  delicate 
  round 
  column, 
  

   two 
  or 
  three 
  joints 
  of 
  which 
  remain 
  attached 
  to 
  one 
  of 
  our 
  speci- 
  

   mens. 
  

  

  Subradials, 
  three 
  hexagonal, 
  counting 
  three 
  angles 
  below, 
  and 
  two 
  

   on 
  the 
  posterior 
  side 
  heptagonal, 
  length 
  and 
  breadth 
  about 
  equal. 
  

  

  Kadials 
  pentangular, 
  nearly 
  twice 
  as 
  wide 
  as 
  long, 
  except 
  the 
  two 
  

   posterior 
  ones, 
  which 
  are 
  rather 
  narrower 
  than 
  the 
  others. 
  

  

  Brachials 
  about 
  the 
  same 
  size 
  and 
  form 
  as 
  the 
  radials, 
  and 
  sup- 
  

   port 
  on 
  their 
  upper 
  sloping 
  sides 
  the 
  first 
  arm 
  plates. 
  Arms 
  two 
  to 
  

   each 
  ray, 
  composed 
  of 
  quadrangular 
  joints 
  that 
  gradually 
  diminish 
  

   in 
  width 
  to 
  their 
  extremities. 
  

  

  Anals, 
  three 
  visible 
  ; 
  the 
  first 
  is 
  nearly 
  as 
  large 
  as 
  the 
  radial 
  

   plates, 
  pentagonal 
  and 
  situated 
  as 
  in 
  Poteriocrinus, 
  between 
  two 
  of 
  

   the 
  subradials, 
  and 
  partly 
  under 
  the 
  left 
  side 
  of 
  the 
  right 
  posterior 
  

   radial. 
  The 
  second 
  is 
  about 
  half 
  as 
  large 
  as 
  the 
  first, 
  and 
  rests 
  on 
  

   the 
  upper 
  truncated 
  margin 
  of 
  the 
  left 
  posterior 
  subradial. 
  The 
  

   third 
  is 
  very 
  small, 
  and 
  rests 
  upon 
  the 
  upper 
  angle 
  of 
  the 
  first 
  

   anal. 
  

  

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

  

  No. 
  2,444, 
  Illinois 
  State 
  collection. 
  

  

  