﻿21 
  i 
  PALEONTOLOGY 
  OF 
  ILLINOI 
  

  

  margin, 
  showing 
  that 
  the 
  formative 
  nucleus 
  wis 
  situated 
  

   midway 
  the 
  anterior 
  margin 
  ; 
  in 
  excessively 
  worn 
  individuals, 
  whether 
  

   from 
  use 
  or 
  abrasion 
  subsequent 
  io 
  dislodgement 
  from 
  the 
  jaw, 
  the 
  

  

  rterior 
  margin 
  presents 
  a 
  broad 
  convexity 
  between 
  th. 
  

   lateral 
  angles, 
  markedly 
  in 
  contrast 
  with 
  the 
  actual 
  curvature- 
  in 
  

  

  h. 
  ^ 
  small 
  tooth 
  measures 
  in 
  greatest 
  diameter 
  acr 
  

   the 
  posterior 
  margin 
  29 
  millimetres, 
  length 
  along 
  inner 
  border 
  about 
  

   16 
  mm. 
  The 
  perfect 
  state 
  of 
  preservation 
  of 
  many 
  of 
  the 
  specim< 
  

   ttffordfa 
  fine 
  exhibition 
  of 
  the 
  character 
  of 
  the 
  inferior 
  surface, 
  i 
  */ 
  

  

  Which 
  is 
  applicable 
  to 
  all 
  the 
  of 
  the 
  genus 
  to 
  

  

  degree. 
  Conforming 
  in 
  a 
  general 
  way 
  to 
  the 
  coronal 
  contour, 
  it 
  

   enveloped 
  in 
  a 
  thin 
  smooth 
  layer 
  of 
  dense 
  matter 
  faintly 
  striated 
  

   Longitudinally, 
  forming 
  a 
  low 
  ridge 
  or 
  angulation 
  about 
  one-third 
  

   the 
  distance 
  from 
  the 
  inner 
  border 
  from 
  whirl, 
  tfa 
  mlarly 
  

  

  slopes 
  to 
  the 
  lateral 
  borders, 
  the 
  tooth 
  showing 
  its 
  maximum 
  depth 
  

   at 
  the 
  posterior 
  margin. 
  

  

  Teeth 
  supposed 
  to 
  have 
  been 
  opposed 
  to 
  the 
  preceding 
  form, 
  or 
  

   pertaining 
  to 
  the 
  mandible, 
  are 
  distinguished 
  by 
  their 
  subquadran- 
  

   gular 
  outline 
  and 
  relatively 
  narrower 
  transverse 
  dian 
  mpared 
  

  

  the 
  length. 
  The 
  anterior 
  margin 
  is 
  broadly 
  arched 
  forward 
  with 
  

   a 
  slight 
  concavity 
  near 
  the 
  inner 
  angle, 
  which 
  is 
  slightly 
  aur.cu 
  

   and 
  sharply 
  roundel 
  at 
  the 
  outer 
  angle: 
  the 
  posterior 
  margm 
  pre- 
  

   sents 
  essentially 
  the 
  same 
  outline, 
  both 
  margins 
  faintly 
  channeled, 
  

   the 
  posterior 
  one 
  most 
  strongly 
  inbeveled, 
  the 
  anterior 
  nearly 
  < 
  

   (deal 
  The 
  inner 
  border 
  is 
  nearly 
  straight, 
  making 
  a 
  fa.nt 
  angula- 
  

   tion 
  ., 
  uttle 
  posterior 
  of 
  the 
  middle 
  in 
  medium. 
  th, 
  a 
  slight 
  

   articular 
  fact 
  occurring 
  at 
  the 
  truncated 
  posterior 
  angle, 
  tl, 
  

   alar 
  face 
  faintly 
  channeled 
  and 
  somewhat 
  y 
  inbeveled; 
  

   border 
  very 
  gently 
  arched 
  and 
  gradually 
  converging 
  anteriorly, 
  basal 
  

  

  p 
  0r 
  ti 
  0n 
  in 
  small 
  and 
  medium-size 
  teeth 
  rather 
  deeply 
  channeled, 
  m 
  

  

  larger 
  specimens 
  showing 
  a 
  thick 
  rim 
  extending 
  considerably 
  beyond 
  

   the 
  00^8] 
  limits 
  and 
  terminating 
  in 
  a 
  produced 
  Bpur 
  

   The 
  coronal 
  Burface 
  is 
  very 
  gently 
  arched 
  longitudinally 
  for* 
  

   from 
  the 
  rather 
  Bteep 
  declivity 
  bordering 
  the 
  poster* 
  -d 
  

  

  rsely, 
  a 
  narrow 
  channel 
  l> 
  

   Which, 
  tO 
  -th 
  the 
  an.er. 
  

  

  defined 
  by 
  an 
  abrupt 
  angle, 
  the 
  coronal 
  enamel 
  formin, 
  

   f()M 
  encircling 
  the 
  tooth; 
  along 
  the 
  exterior 
  border 
  th, 
  i 
  

  

  linarily 
  abruptly 
  rounded 
  to 
  the 
  angular 
  dema 
  

  

  and 
  I,,-, 
  hut 
  in 
  ll 
  

  

  nal 
  limit 
  till 
  well 
  defined 
  ; 
  a 
  Bhghl 
  la 
  

  

  