﻿PALEONTOLOGY 
  OF 
  ILLINOIS. 
  

  

  posterior 
  angle, 
  and 
  marked 
  above 
  l>y 
  the 
  narrow 
  enameled 
  fold 
  which 
  

   is 
  defined 
  from 
  the 
  basal 
  portion 
  by 
  a 
  slight 
  channel; 
  anterolateral 
  

   border 
  forming 
  a 
  vertical 
  face 
  at 
  the 
  inner 
  angle, 
  gradually 
  sloping 
  

   upward 
  and 
  backward 
  toward 
  the 
  outer 
  extremity, 
  and, 
  save 
  a 
  nar- 
  

   row 
  belt 
  along 
  the 
  inferior 
  edge, 
  enveloped 
  in 
  the 
  enamel 
  fold, 
  which 
  

   is 
  also 
  well 
  defined 
  from 
  the 
  basal 
  rim. 
  Coronal 
  region 
  traversed 
  

   longitudinally 
  by 
  a 
  moderately 
  prominent, 
  transversely 
  arched 
  median 
  

   ridge, 
  the 
  axis 
  of 
  which 
  lies 
  nearest 
  the 
  anterolateral 
  border, 
  and 
  

   sharply 
  defined 
  on 
  either 
  side 
  by 
  an 
  angulation 
  or 
  narrow 
  grooi 
  

   anterior 
  belt 
  relatively 
  narrow, 
  very 
  faintly 
  arched 
  transversely, 
  or 
  

   nearly 
  plane, 
  and 
  scarcely 
  half 
  the 
  width 
  of 
  the 
  median-lobe; 
  pos- 
  

   terior 
  alation 
  about 
  the 
  same 
  width 
  as 
  the 
  median-lobe, 
  transversely 
  

   concave 
  and 
  merged 
  into 
  the 
  posterior 
  depression 
  from 
  which 
  it 
  

   steeply 
  rises 
  into 
  the 
  produced 
  posterior 
  angle. 
  Surface 
  finely 
  punc- 
  

   tate. 
  Greatest 
  length 
  of 
  tooth 
  along 
  postero-lateral 
  border, 
  40 
  mm.; 
  

   ditto, 
  antero-lateral 
  border, 
  30 
  mm. 
  : 
  breadth 
  across 
  inner 
  margin, 
  

   23 
  mm.; 
  greatest 
  height 
  of 
  antero-lateral 
  border, 
  8 
  mm. 
  

  

  Maxillary 
  posterior 
  teeth 
  subspatulate 
  in 
  outline, 
  strongly 
  from 
  

   within 
  outwards, 
  outer 
  margin 
  strongly 
  inrolled; 
  postero-lateral 
  

   border 
  making 
  a 
  broad 
  curve 
  outward 
  and 
  forward 
  from 
  the 
  obtusely 
  

   pointed 
  posterior 
  angle 
  to 
  point 
  of 
  inrollment, 
  then--, 
  to 
  the 
  anterior 
  

   ;le 
  the 
  outline 
  is 
  slightly 
  concave: 
  inner 
  margin 
  arched 
  round 
  

   the 
  base 
  of 
  the 
  coronal 
  prominence, 
  and 
  thi 
  i 
  rly 
  straight 
  to 
  

  

  the 
  anterior 
  border 
  ; 
  antero-lateral 
  border 
  slightly 
  obliquely 
  truncated 
  

   from 
  the 
  inner 
  to 
  the 
  outer 
  angle, 
  and 
  equal 
  to 
  about 
  two-thirds 
  the 
  

   diameter 
  of 
  the 
  tooth 
  along 
  a 
  line 
  diagonal 
  to 
  the 
  direction 
  of 
  inroll- 
  

   ment 
  across 
  the 
  posterior 
  ridge. 
  Posterior 
  lobe 
  of 
  the 
  crown 
  occu- 
  

   pying 
  little 
  more 
  than 
  one-third 
  the 
  total 
  breadth 
  of 
  the 
  tooth, 
  

  

  moderately 
  arched 
  transversely, 
  the 
  ores! 
  culminating 
  in 
  front 
  win 
  

   the 
  surface 
  rapidly 
  descends 
  into 
  the 
  narrow 
  furrow 
  defining 
  it 
  from 
  

   the 
  subordinate 
  ridge, 
  winch 
  latter 
  presents 
  a 
  nearly 
  uniform 
  con- 
  

   vexity, 
  gradually 
  narrowing 
  from 
  within 
  outward, 
  and. 
  in 
  perfi 
  

  

  oimens, 
  defined 
  in 
  front 
  by 
  a 
  distinct 
  though 
  slight 
  angulation; 
  

   anterior 
  neck 
  nearly 
  amooth, 
  with 
  a 
  f< 
  w 
  obscun 
  i 
  ines 
  along 
  

  

  tli< 
  inner 
  margin, 
  destitute 
  of 
  revolt 
  Breadth 
  of 
  a 
  medium* 
  

  

  size 
  tooth 
  between 
  the 
  inner 
  angles, 
  i 
  s 
  nun.: 
  breadth 
  of 
  tooth 
  aoro 
  

   th« 
  r 
  prominence 
  diagonal 
  to 
  the 
  inrollment, 
  20 
  mm.: 
  length 
  

  

  along 
  antero-lateral 
  borders, 
  18 
  nun. 
  

  

  Maxillary 
  median 
  teeth 
  forming 
  a 
  triangular 
  plate 
  articulating 
  

   with 
  tin 
  posterior 
  tooth 
  by 
  th< 
  lateral 
  bolder, 
  the 
  

  

  