﻿PALEONTOLOGY 
  OF 
  ILLINOIB. 
  

  

  tance; 
  near 
  the 
  borders 
  the 
  surface 
  is 
  depressed 
  and 
  defined 
  from 
  

   the 
  projecting 
  basal 
  rim 
  by 
  a 
  delicate 
  fold, 
  the 
  enamel 
  te 
  rmin 
  a 
  tin 
  g 
  

   in 
  an 
  acute 
  angle 
  at 
  the 
  postero-lateral 
  extremities. 
  The 
  Burma 
  

   usually 
  worn, 
  exposing 
  the 
  minute, 
  irregular 
  punets, 
  the 
  lateral 
  

  

  s 
  and 
  inner 
  margin 
  retaining 
  greater 
  or 
  

   in 
  the 
  superficial 
  enamel 
  layer, 
  which 
  Bhows 
  exceedingly 
  delic 
  

   ruga 
  radiating 
  towards 
  the 
  lateral 
  and 
  posterior 
  sides. 
  Inferior 
  

   Burface 
  corresponding 
  in 
  longitudinal 
  concavity 
  to 
  th< 
  convexity 
  of 
  

   the 
  crown, 
  trai 
  ntly 
  arched 
  with 
  a 
  slight 
  median 
  angula- 
  

  

  lation, 
  the 
  dense 
  external 
  layer 
  smooth 
  or 
  faintly 
  flul 
  ntudin- 
  

  

  ally. 
  A 
  large 
  tooth 
  measures 
  in 
  greatest 
  transversa 
  diameter 
  between 
  

   the 
  posterior 
  cornua 
  -it) 
  millimetres; 
  the 
  enameled 
  coronal 
  area 
  

   shows 
  a 
  breadth 
  of 
  13.5 
  mm.; 
  length 
  of 
  tooth 
  along 
  the 
  median 
  

   line 
  15 
  mm.; 
  depth 
  at 
  the 
  posterior 
  margin 
  -I 
  mm. 
  

  

  fch, 
  referable 
  to 
  the 
  mandible 
  of 
  the 
  same 
  species 
  that 
  bore 
  the 
  

   preceding 
  form, 
  which 
  they 
  resemble 
  in 
  outline 
  and 
  coronal 
  as]. 
  

   are 
  specially 
  distinguished 
  by 
  their 
  relatively 
  breadth 
  com- 
  

  

  pared 
  with 
  the 
  length, 
  and 
  rather 
  Btrongly 
  rolled 
  contour 
  of 
  the 
  

   crown 
  from 
  behind 
  forwards. 
  The 
  anterior 
  margin 
  is 
  somewhal 
  

   Btrongly 
  arched 
  forward 
  from 
  the 
  slight 
  auriculate 
  antero-lateral 
  

   angl' 
  -. 
  meeting 
  in 
  a 
  rounded 
  angulation 
  at 
  the 
  median 
  line, 
  the 
  in- 
  

   beveled 
  coronal 
  portion 
  forming 
  a 
  well-defined 
  narrow 
  belt, 
  beneath 
  

   which 
  extends 
  tin 
  deep 
  border 
  of 
  the 
  Blightly 
  channeled 
  basal 
  por- 
  

   tion, 
  in 
  which 
  particulars 
  also 
  then 
  is 
  unmistakable 
  identity 
  with 
  

   the 
  preceding 
  form; 
  the 
  lateral 
  borders 
  gradually 
  converge, 
  making 
  

   obtuse 
  angles 
  in 
  front 
  and 
  posteriorly 
  produced, 
  the 
  l>a>al 
  rim 
  form- 
  

   ing 
  a 
  conspicuous 
  border, 
  Blightly 
  upraised 
  along 
  the 
  outer 
  side. 
  

   rounded 
  below 
  and 
  merged 
  into 
  the 
  inferior 
  surface; 
  posterior 
  mar- 
  

   gin 
  unknown 
  probably 
  approximating 
  tin 
  curvature 
  of 
  the 
  opp< 
  

   kremity. 
  Coronal 
  surface 
  strongly 
  arched 
  longitudinally, 
  th< 
  

  

  verse 
  convexity 
  mod. 
  rate 
  and 
  regular, 
  with 
  a 
  shallow, 
  narrow 
  

  

  presBion 
  parallel 
  withthi 
  lateral 
  borders, 
  along 
  which 
  anexoeedii 
  

  

  lid 
  defines 
  the 
  crown 
  from 
  tin 
  hasal 
  rim: 
  in 
  front 
  the 
  

  

  Burface 
  is 
  worn 
  into 
  a 
  lunate 
  depression 
  of 
  greater 
  or 
  tenl 
  

  

  and 
  depth, 
  the 
  punctaa 
  and 
  th. 
  delicate 
  m 
  aamentation 
  of 
  the 
  

  

  with 
  the 
  Burface 
  app< 
  ; 
  in 
  the 
  

  

  opposed 
  form. 
  the 
  posterior 
  margin 
  the 
  Burfaci 
  Bhows 
  I 
  

  

  tinct 
  i 
  th, 
  making 
  a 
  broad 
  arch 
  backward, 
  and 
  .1 
  

  

  ,,n 
  era! 
  borders, 
  bul 
  which 
  does 
  not 
  1 
  ly 
  in. 
  li- 
  

  

  ne 
  outline 
  of 
  the 
  posterior 
  margin, 
  which 
  doubtless 
  in 
  the 
  

  

  to 
  the 
  convex 
  out- 
  

  

  