﻿164 
  PALEONTOLOGY 
  OF 
  ILLINOIS. 
  

  

  or 
  slightly 
  produced 
  beyond 
  the 
  coronal 
  limits 
  posteriorly. 
  Anterior 
  

   ridge 
  occupying 
  more 
  than 
  half 
  the 
  transverse 
  diameter 
  of 
  the 
  cor- 
  

   onal 
  surface, 
  transversely 
  arched, 
  abruptly 
  sloping 
  in 
  front 
  to 
  the 
  

   anterior 
  articular 
  border, 
  more 
  gently 
  declining 
  into 
  the 
  posterior 
  de. 
  

   ion 
  from 
  which 
  the 
  Buddenly-upraised, 
  narrow 
  alate 
  lobe 
  is 
  de- 
  

   fined 
  by 
  a 
  distinct 
  angulation. 
  Surface 
  minutely 
  and 
  closely 
  punc- 
  

   tate, 
  and 
  further 
  marked 
  by 
  more 
  or 
  less 
  distinct 
  trane 
  indu- 
  

   ctions 
  conforming 
  to 
  the 
  inner 
  margin, 
  usually 
  obso!. 
  r 
  the 
  

   greater 
  extent 
  of 
  the 
  coronal 
  region. 
  A 
  specimen 
  of 
  ordinary 
  size 
  

   shows, 
  a 
  length 
  along 
  the 
  coronal 
  ridge 
  of 
  about 
  23 
  mm; 
  trans 
  

   diameter 
  at 
  the 
  inner 
  margin, 
  11 
  mm. 
  

  

  Posterior 
  tooth 
  of 
  the 
  mandible 
  proportionately 
  agreeing 
  in 
  size 
  

   with 
  the 
  opposed 
  maxillary 
  teeth, 
  trapezoidal 
  in 
  general 
  outline, 
  of 
  

   great 
  transverse 
  diameter 
  at 
  the 
  inner 
  margin 
  as 
  compared 
  t<> 
  the 
  

   length 
  along 
  the 
  antero-latcral 
  border, 
  strongly 
  inrolled 
  and 
  arched 
  

   longitudinally. 
  Antero-lateral 
  border 
  obliquely 
  produced 
  outward 
  and 
  

   forward 
  from 
  the 
  obtuse 
  inner 
  angle, 
  enamel 
  fold 
  forming 
  a 
  narrow, 
  

   rounded 
  belt 
  inbeveled 
  to 
  the 
  slightly-chainulcd 
  basal 
  rim. 
  which 
  it 
  

   equals 
  in 
  depth; 
  inner 
  margin 
  very 
  obliquely 
  produced 
  backward 
  

   from 
  the 
  anterior 
  angle, 
  broadly 
  arched 
  round 
  the 
  base 
  of 
  the 
  cor- 
  

   onal 
  prominence 
  with 
  a 
  slight 
  concavity 
  in 
  passing 
  the 
  posterior 
  

   coronal 
  depression 
  into 
  the 
  moderately 
  produced, 
  acutely 
  rounded 
  

   posterior 
  extremity, 
  interiorly 
  inbeveled; 
  postero-lateral 
  border 
  very 
  

   rapidly 
  converging 
  toward 
  the 
  outer 
  inrolled 
  margin, 
  gently 
  ci 
  

   and 
  ni 
  arly 
  parallel 
  with 
  the 
  anterior 
  half 
  of 
  the 
  inner 
  margin, 
  the 
  

   narrow, 
  rounded 
  enamel 
  fold 
  inbeveled 
  ami 
  defined 
  by 
  a 
  slight 
  sulcus 
  

   from 
  the 
  basal 
  portion, 
  which 
  forms 
  a 
  shallow 
  rim 
  projecting 
  down- 
  

   ward 
  and 
  outward 
  well 
  beyond 
  the 
  coronal 
  border, 
  in 
  worn 
  ex- 
  

   amples 
  inbeveled. 
  Crown 
  traversed 
  lit 
  arly 
  centrally 
  by 
  a 
  r 
  

  

  prominent 
  regularly 
  transversely 
  arched 
  ridge, 
  the 
  broad 
  Blope 
  de- 
  

   scending 
  to 
  the 
  antero-lateral 
  border, 
  somewhat 
  depressed, 
  more 
  

   abruptly 
  sloping 
  into 
  the 
  posterior 
  depression, 
  beyond 
  which 
  

   the 
  moderately 
  apraised 
  alate 
  expansion 
  of 
  the 
  postero-lateral 
  bor- 
  

   der. 
  Surface 
  closeh 
  and 
  regularly 
  punctate, 
  mature 
  individuals. 
  

  

  oially 
  those 
  iii 
  which 
  the 
  exterior 
  layers 
  bave 
  been 
  exfol 
  

  

  Bhowing 
  more 
  or 
  less 
  distinot 
  Crowded 
  TO 
  :i 
  parallel 
  with 
  the 
  inner 
  

   ill 
  ol 
  the 
  tooth. 
  Ill 
  both 
  of 
  the 
  abo\e 
  described 
  foril 
  

  

  ency 
  to 
  compression 
  or 
  elongation 
  of 
  the 
  pun. 
  ibs< 
  rvable, 
  in 
  

  

  the 
  transverse 
  furrows 
  presenting 
  a 
  very 
  delicate 
  tracer] 
  in 
  some 
  

   pi 
  cimeii 
  of 
  ordinars 
  the 
  inner 
  

  

  ii 
  18 
  mm.; 
  Length 
  of 
  antero-lateral 
  border 
  to 
  the 
  Lnrol 
  

   mai 
  mm, 
  

  

  