﻿PLATE 
  XXXI. 
  

  

  l'v.n. 
  

  

  Fit,'. 
  1. 
  ARCH.EOCIDABIB 
  ILLINOIENSIS 
  338 
  

  

  1 
  a. 
  b. 
  Primary 
  spines 
  natural 
  size. 
  

  

  Fit,'. 
  J. 
  COMPSASTEB 
  FOBM08U8 
  327 
  

  

  Ventral 
  side 
  natural 
  size. 
  

  

  Section 
  of 
  ray 
  enlarged 
  two 
  diameters, 
  

  

  TRKM 
  ATA6TER 
  DIFFICILIB 
  330 
  

  

  V.ntral 
  side 
  magnilk'l 
  tWO 
  diameters. 
  

   Section 
  of 
  ray 
  magnified 
  four 
  dlami 
  

  

  Cholaster 
  peculiabis 
  32» 
  

  

  Dorsal 
  view 
  natural 
  size. 
  

  

  Section 
  of 
  ray 
  magnified 
  two 
  diameters. 
  

  

  HYB0CHINU8 
  8PECTABILI8 
  

  

  View 
  of 
  a 
  depressed 
  specimen 
  natural 
  size. 
  

  

  Views 
  of 
  ambulaoral 
  and 
  adambulaoral 
  plates, 
  enlarged 
  two 
  dianv 
  ■ 
  

  

  Magnified 
  view 
  of 
  horn-like 
  protaberan 
  

  

  View 
  of 
  a 
  crushed 
  specimen, 
  showing 
  the 
  jaw-. 
  

  

  Jaws, 
  belonging 
  to 
  this 
  or 
  a 
  kindred 
  species. 
  

  

  Pebisohosomi 
  - 
  1 
  1 
  1 
  ehoiknsxs 
  sss 
  

  

  View 
  of 
  the 
  apical 
  end 
  of 
  a 
  distorted 
  spocimen, 
  natural 
  size. 
  

  

  Fik' 
  9. 
  E( 
  ![IN"I>I8CU8 
  OPTATU8 
  336 
  

  

  View 
  '>f 
  part 
  of 
  the 
  lower 
  sldi 
  ■ 
  ■'. 
  I 
  -peciinen. 
  showing 
  the 
  plates 
  near 
  

   the 
  margir, 
  natunil 
  I 
  

  

  

  J 
  0. 
  

  

  

  a 
  b. 
  

  

  Fig. 
  

  

  3. 
  

  

  

  3 
  a. 
  

  

  

  8 
  b. 
  

  

  Fir, 
  

  

  1. 
  

  

  

  1 
  ". 
  

  

  

  4 
  b. 
  

  

  PUf. 
  

  

  5. 
  

  

  

  5 
  a. 
  

  

  

  5 
  b.d 
  

  

  

  5 
  0. 
  

  

  Fig. 
  

  

  6, 
  

  

  Fig. 
  

  

  7. 
  

  

  Fig. 
  

  

  8. 
  

  

  

  