﻿•Jin 
  PALiEONTOLOGI 
  OP 
  ELLINOH 
  

  

  the 
  cost* 
  ridges 
  or 
  tubercles, 
  which 
  arc 
  wry 
  appreciably 
  more 
  regu- 
  

   lar 
  ana 
  delioate 
  than 
  is 
  thi 
  in 
  the 
  St. 
  Eonn. 
  The 
  

   magnii 
  of 
  the 
  latter 
  spine 
  belonging 
  to 
  tin- 
  Shumard 
  

   illectioo 
  of 
  Washington 
  University, 
  affords 
  unusually 
  aatiafactory 
  

   d< 
  tails 
  relating 
  to 
  the 
  ornamentation 
  of 
  the 
  exposed 
  pari 
  the 
  

   changes 
  in 
  the 
  superficial 
  characters 
  toward 
  the 
  distal 
  extremity 
  

   ributable 
  to 
  wear, 
  the 
  careful 
  examination 
  of 
  which 
  has 
  led 
  to 
  

   the 
  belief 
  that 
  the 
  spine 
  under 
  consideration 
  belonged 
  to 
  a 
  distinct 
  

  

  cal 
  position 
  and 
  locality 
  : 
  I 
  -ter. 
  Illinois. 
  

  

  OtENAGAHTHUS 
  BUTTBBSI, 
  St. 
  .T. 
  and 
  W. 
  

  

  pi. 
  xxii. 
  Fit. 
  a. 
  

  

  Fin-spine 
  of 
  medium 
  size, 
  stout, 
  slightly 
  arched 
  along 
  the 
  anterior 
  

   gradually 
  tapering, 
  Bubtriangular 
  in 
  cross 
  section 
  ; 
  the 
  imbedded 
  

   mal 
  extremity 
  much 
  more 
  rapidly 
  fa 
  gently 
  depn 
  

  

  below 
  the 
  anterior 
  shoulder, 
  relatively 
  m 
  inded 
  and 
  triangular 
  

  

  in 
  section, 
  the 
  dorsal 
  line 
  making 
  a 
  broad 
  curve, 
  t 
  j 
  immitant 
  

  

  plain 
  spaoe 
  reaching 
  high 
  up 
  toward 
  the 
  distal 
  extremity 
  

   yond 
  the 
  point 
  of 
  incloaure 
  of 
  the 
  pulp 
  cavity. 
  The 
  pulp 
  cavity 
  is 
  

   inclosed 
  posteriorly 
  for 
  only 
  a 
  comparatively 
  sh' 
  ace 
  from 
  the 
  

  

  apex, 
  where 
  it 
  opens 
  out. 
  forming 
  thence 
  a 
  deep 
  angular 
  trench 
  in 
  

   posterior 
  face 
  reaching 
  to 
  the 
  proximal 
  extremity; 
  its 
  section 
  ap- 
  

   proximates 
  that 
  of 
  the 
  external 
  walls, 
  its 
  dimensions 
  and 
  poe 
  

  

  shown 
  in 
  the 
  section 
  diagrams 
  introduced 
  with 
  the 
  illustrations 
  

   of 
  the 
  type 
  specimen. 
  Tin 
  posterior 
  face 
  appears 
  to 
  be 
  slightly 
  

   convex 
  transversely 
  and 
  sharply 
  rounded 
  at 
  the 
  Lateral 
  angles, 
  the 
  

   specimens 
  nol 
  Bhowing 
  denticles, 
  if 
  indeed 
  such 
  exist 
  The 
  lal 
  

   Burfacea 
  aw 
  gently 
  convex 
  and 
  more 
  or 
  less 
  obtusely 
  rounded 
  along 
  

   the 
  anterior 
  edge 
  which 
  bean 
  a 
  single 
  longitudinal 
  rib;th< 
  

   surface 
  is 
  regularly 
  and 
  somewhat 
  strongly 
  ribbed, 
  the 
  

   moderate 
  prominence 
  and 
  convexity, 
  with 
  narrow 
  intercostal 
  fur 
  

   mm 
  1 
  eh,, 
  :iy 
  bifurcating 
  n 
  • 
  ir 
  thi 
  

  

  -hurt 
  implanted 
  occur 
  somewhat 
  suddenly 
  deflected 
  to 
  the 
  

  

  narrow, 
  plain 
  bell 
  bordering 
  either 
  post 
  *hieh 
  

  

  abruptly 
  lb.- 
  anterior 
  | 
  ronn. 
  

  

  tubercles, 
  winch 
  havt 
  a 
  obliqui 
  

  

  i 
  and 
  upward, 
  the 
  ores! 
  oulminatin 
  

   p. 
  . 
  and 
  delicately 
  sculptured 
  bj 
  radial 
  i 
  kne 
  

  

  