﻿868 
  

  

  PAL.KoNTOLOGY 
  OF 
  ILLINOIS. 
  

  

  l-'.i.i 
  ,.\c 
  IBXHUB 
  ohovatts, 
  Larris., 
  Nov. 
  Bp. 
  

  

  

  

  Body 
  obovatc 
  or 
  elongate-baloon 
  Bhaped, 
  

   more 
  than 
  once 
  and 
  a 
  half 
  as 
  long 
  a- 
  wide; 
  

   upper 
  half 
  wider 
  than 
  the 
  lower, 
  Bemiovoid 
  ; 
  

   test 
  width 
  at 
  ahout 
  two-thinls 
  from 
  the 
  

   base; 
  lower 
  half 
  gradually 
  increasing 
  in 
  

   width 
  to 
  the 
  distal 
  end 
  of 
  the 
  ambulacra 
  ; 
  

   base 
  truncate 
  with 
  a 
  deep 
  concavity 
  which 
  is 
  

   fdled 
  by 
  the 
  column. 
  Ci 
  on 
  pen- 
  

  

  jL 
  cross 
  geotton 
  of 
  1 
  1 
  . 
  . 
  - 
  tangular. 
  with 
  straight 
  or 
  very 
  slightly 
  COB- 
  

  

  hvilrospiri 
  .< 
  ob- 
  ° 
  ' 
  ° 
  - 
  

  

  dTSSSuS™ 
  11, 
  BnU,r8ed 
  :w 
  " 
  vex 
  sides, 
  except 
  along 
  the 
  basala, 
  where 
  

  

  the 
  sides 
  are 
  somewhat 
  concave, 
  and 
  the 
  section 
  more 
  stellate. 
  

  

  Basalfl 
  deeply 
  imbedded 
  within 
  the 
  columnar 
  cavity, 
  the 
  outer 
  

   angles 
  barely 
  reaching 
  the 
  margin. 
  Radials 
  comparatively 
  small: 
  

   length 
  twice 
  their 
  width 
  at 
  the 
  bari-radial 
  suture, 
  gradually 
  in. 
  i 
  

   rag 
  upward, 
  BO 
  that 
  the 
  forks 
  or 
  limits 
  at 
  their 
  apper 
  side 
  are 
  ahout 
  

   equal 
  in 
  width 
  to 
  the 
  body 
  of 
  the 
  plate 
  at 
  its 
  lower 
  side. 
  The 
  lat- 
  

   eral 
  sides 
  are 
  somewhat 
  thickened 
  at 
  the 
  upper 
  face 
  of 
  the 
  i 
  

   more 
  particularly 
  toward 
  the 
  lower 
  end 
  of 
  the 
  plate, 
  where 
  they 
  

   produce 
  indistinct 
  ridges 
  at 
  the 
  suture 
  lines. 
  The 
  upper 
  side 
  of 
  the 
  

   limbs 
  is 
  gracefully 
  curved 
  in 
  an 
  upward 
  direction, 
  with 
  re-entering 
  

   angles 
  toward 
  the 
  lateral 
  sutures, 
  and 
  deeper 
  ones 
  toward 
  the 
  radial 
  

   Binuses. 
  From 
  the 
  bottom 
  of 
  the 
  plate 
  tliere 
  extends 
  to 
  the 
  radial 
  

   Minis 
  (whioh 
  in 
  this 
  species 
  is 
  about 
  half 
  way 
  to 
  the 
  top 
  of 
  the 
  

   limbs), 
  a 
  conspicuous 
  rounded 
  ridge, 
  ending 
  in 
  a 
  very 
  prom 
  

   lip, 
  and 
  it 
  is 
  tbis 
  .structure 
  mainly 
  which 
  produces 
  the 
  truncation 
  

  

  toward 
  the 
  basal 
  region, 
  which 
  otherwise 
  would 
  not 
  be 
  

   tible. 
  

   oral 
  or 
  deltoid 
  pieces 
  large, 
  measuring 
  almost 
  Four-fifths 
  the 
  

  

  h 
  of 
  tbe 
  body; 
  broad 
  lanceolate. 
  The 
  four 
  regular 
  orals 
  have 
  

   a 
  length 
  equal 
  to 
  twice 
  their 
  greatest 
  width. 
  The 
  fifth, 
  that 
  of 
  the 
  

  

  nor 
  Bide, 
  which 
  in 
  this 
  genua 
  is 
  divided 
  throughout 
  its 
  full 
  

   anal 
  plate, 
  occupies, 
  including 
  the 
  latt 
  

   greater 
  width 
  than 
  the 
  four 
  regular 
  orals, 
  and 
  the 
  two 
  halvt 
  

   narrower 
  at 
  any 
  place 
  than 
  the 
  intcrpos, 
  d 
  anal 
  plate. 
  The 
  

  

  i, 
  lanceolate, 
  <»f 
  nearly 
  equal 
  width 
  throughout, 
  slightly 
  tapering 
  at 
  

   the 
  upper 
  end. 
  Its 
  lower 
  ride 
  rests 
  on 
  the 
  same 
  surface 
  with 
  the 
  

   other 
  plat.', 
  but 
  gradually 
  ri>e> 
  above 
  the 
  general 
  level 
  and 
  at 
  the 
  

  

  