﻿232 
  PALEONTOLOGY 
  OF 
  ILLINOIS. 
  

  

  Mandibular 
  teeth 
  subquadrangular 
  in 
  outline, 
  rather 
  - 
  

  

  arched 
  from 
  within 
  outward. 
  Lateral 
  borders 
  unknown. 
  The 
  ant 
  

  

  and 
  posterior 
  mar-ins 
  marked 
  by 
  a 
  narrov. 
  .1 
  fold 
  veil 
  

  

  defined 
  from 
  the 
  basal 
  portion, 
  which 
  latter 
  in 
  fr 
  ttly 
  

  

  channeled 
  with 
  a 
  corresponding 
  convexity 
  aloi 
  r 
  mar- 
  

  

  gin. 
  The 
  coronal 
  region, 
  besides 
  the 
  rather 
  Btrong 
  longitudinal 
  

   hingi 
  | 
  a 
  -.nth 
  transverse 
  convexity, 
  which 
  probably 
  

  

  occupies 
  the 
  greater 
  extent 
  of 
  dhe 
  coronal 
  area. 
  The 
  anterior 
  half 
  

   or 
  more 
  of 
  the 
  surface 
  is 
  occupied 
  by 
  a 
  tr 
  

  

  behind 
  Which 
  the 
  surface 
  steeply 
  slopes 
  to 
  8 
  ffid< 
  plan 
  

  

  dering 
  the 
  posterior 
  margin, 
  presenting 
  a 
  oontour 
  

  

  ding 
  p. 
  that 
  of 
  mature 
  examples 
  of 
  the 
  opposite 
  jaw. 
  I 
  ho 
  

   rugose 
  ornamentation 
  and 
  punetationof 
  the 
  coronal 
  surf;; 
  

  

  a 
  repetition 
  of 
  the 
  characters 
  noted 
  in 
  O0nn< 
  ction 
  with 
  the 
  maxilll 
  

   form. 
  The 
  imperfect 
  sole 
  representative 
  of 
  the 
  form 
  Bhows 
  a 
  loi 
  

   tudinal 
  diameter 
  of 
  90 
  millimetres, 
  indicating 
  the 
  huge 
  dimensions 
  

   attained 
  by 
  the 
  fishes 
  represented 
  by 
  the 
  present 
  teeth, 
  and 
  which 
  

   was, 
  SO 
  far 
  as 
  we 
  are 
  aware, 
  the 
  largest 
  of 
  its 
  Kind. 
  

   The 
  above 
  species 
  is 
  known 
  to 
  us 
  from 
  a 
  couple 
  ol 
  

   referable 
  to 
  the 
  upper 
  jaw. 
  and 
  a 
  narrow 
  section 
  of 
  a 
  

   men 
  belonging 
  to 
  the 
  opposite 
  jaw 
  or 
  mandible. 
  Thi 
  rof 
  the 
  

  

  maxillary 
  teeth 
  shows 
  scarcely 
  a 
  vestige 
  of 
  the 
  n 
  J 
  orna- 
  

  

  mentation, 
  the 
  surface 
  on 
  the 
  contrary 
  being 
  densely 
  I 
  

   the 
  exposed 
  orifices 
  of 
  the 
  vertical 
  tubes, 
  which 
  exhibit 
  varioufi 
  

   of 
  wear 
  from 
  the 
  simple 
  punctaof 
  excessively 
  abrad 
  

   crater-like 
  form 
  surrounded 
  by 
  a 
  rim 
  of 
  intensely 
  hard 
  sul 
  

   the 
  punctw 
  simple 
  or 
  confluent, 
  with 
  discernible 
  b 
  

   prismatic 
  structure. 
  We 
  are 
  inclined 
  to 
  regard 
  this 
  

  

  liflBimilar 
  in 
  its 
  superficial 
  ai 
  

   with 
  its 
  associates. 
  It 
  is 
  an 
  extremely 
  ran 
  . 
  and 
  w 
  

  

  the 
  lack 
  of 
  materials 
  necessary 
  for 
  a 
  comparison 
  with 
  I 
  

   the 
  typical 
  European 
  species 
  with 
  which 
  it 
  - 
  of 
  

  

  emblan 
  

  

  ion 
  and 
  locaUtie*: 
  Keokuk 
  limestone, 
  I 
  ami 
  

  

  Bentonsport, 
  [owa. 
  

  

  

  