﻿l'AL.LoNTOLoC.Y 
  OF 
  ILLINOIS. 
  

  

  ESOHINODIBGUB 
  OPTATU8, 
  Sp. 
  HOV. 
  

  

  PL 
  XXM. 
  Pig. 
  9, 
  view 
  of 
  part 
  of 
  the 
  

   marfrln. 
  

  

  ly 
  discoid, 
  rather 
  large, 
  being 
  more 
  than 
  an 
  inch 
  in 
  diam 
  

   and 
  having 
  large 
  plates 
  in 
  the 
  interambnlaeral 
  Killer 
  

  

  outs 
  on 
  other 
  parte 
  of 
  the 
  test. 
  The 
  margin 
  is 
  compi 
  small 
  

  

  plates 
  elongated 
  in 
  the 
  direction 
  of 
  the 
  oircumfi 
  and 
  forming 
  

  

  mi-cylindrical 
  or 
  ronnded 
  rim. 
  but 
  not 
  attaching 
  to 
  other 
  ob 
  

   showing 
  that 
  if 
  the 
  Bpeeies 
  was 
  sessile 
  it 
  did 
  not 
  unite 
  l>y 
  the 
  whole 
  

   underside, 
  as 
  in 
  Agelacrinus. 
  

  

  Interambulacral 
  areas 
  depressed, 
  concave, 
  covered 
  with 
  p 
  

   plates, 
  those 
  in 
  the 
  central 
  part 
  large, 
  while 
  those 
  in 
  the 
  ma 
  

   are 
  smaller, 
  and 
  appear 
  as 
  if 
  trimmed 
  to 
  a 
  - 
  r 
  the 
  

  

  reception 
  of 
  the 
  ambulacra. 
  

  

  The 
  ambulacra 
  are 
  lopg, 
  Blender, 
  curving, 
  angular 
  ar< 
  

   within 
  the 
  faoe 
  of 
  the 
  disc, 
  and 
  joined 
  with 
  the 
  interambu!. 
  

   plates 
  by 
  straight 
  lines, 
  without 
  interlocking 
  or 
  imbric 
  

   They 
  are 
  composed 
  on 
  each 
  Bide 
  of 
  alternately 
  longer 
  and 
  b! 
  

  

  a 
  which 
  interlock 
  at 
  the 
  angular 
  arch, 
  with 
  each 
  other 
  and 
  

   with 
  smaller 
  intercalated 
  plates, 
  so 
  as 
  to 
  giv< 
  

   the 
  dovetailing 
  union 
  of 
  the 
  plates 
  on 
  the 
  Burfaoi 
  h 
  ambu- 
  

  

  lacrum. 
  The 
  ambulacra 
  do 
  not 
  a 
  riniu, 
  fr> 
  

  

  central 
  pyramid, 
  but 
  the 
  divisions 
  take 
  place 
  near 
  the 
  central 
  p 
  

  

  the 
  disc, 
  separated 
  by 
  numerous 
  ambulacra! 
  plates, 
  and 
  on 
  diff< 
  

  

  of 
  the 
  mouth. 
  The 
  manner 
  of 
  bifurcation 
  n 
  

   in 
  this 
  way: 
  a 
  division 
  takes 
  place 
  on 
  one 
  side 
  of 
  the 
  mouth, 
  from 
  

   win 
  nee 
  two 
  ambula 
  1 
  an 
  

  

  ambulacra] 
  ted 
  past 
  the 
  mouth 
  ; 
  at 
  tli. 
  

  

  tanoe 
  of 
  one-tenth 
  of 
  an 
  inch 
  it 
  throws 
  off, 
  in 
  the 
  dii 
  

   the 
  mouth, 
  a 
  curving 
  ambulacrum 
  and 
  continuing 
  

   mouth, 
  at 
  tl 
  of 
  another 
  tenth 
  of 
  an 
  inch 
  it 
  divides 
  into 
  

  

  two 
  ambulacra. 
  This 
  leaves 
  the 
  mouth 
  in 
  the 
  wider 
  interambu- 
  

  

  The 
  month 
  would 
  seem, 
  from 
  the 
  condition 
  of 
  

   Bntral, 
  but 
  it 
  may 
  I 
  itly 
  Bubcentral. 
  It 
  con 
  n 
  the 
  

  

  of 
  an 
  elongated 
  < 
  levation 
  

  

  maili 
  r 
  ported 
  on 
  I 
  

  

  i 
  number 
  of 
  pli 
  of 
  whi< 
  

  

  of 
  which 
  are 
  nol 
  d( 
  

  

  