﻿00 
  PALAEONTOLOGY 
  OF 
  ILLINOIS. 
  

  

  rounded 
  or 
  sigmoidally 
  curved 
  from 
  the 
  obtuse 
  anterior 
  angle 
  into 
  

   the 
  more 
  acute 
  extremity 
  of 
  the 
  posterior 
  wing. 
  Coronal 
  i 
  

   presenting 
  three 
  divisions, 
  all 
  regularly 
  narrowing 
  toward 
  thi 
  

   extremity, 
  viz: 
  In 
  front, 
  a 
  narrow 
  transversely 
  plane 
  tx 
  

   or 
  less 
  prominent 
  median 
  ridge 
  denned 
  in 
  front 
  by 
  a 
  slight 
  angula- 
  

   tion 
  from 
  the 
  anterior 
  belt, 
  and 
  sloping 
  posteriorly 
  into 
  the 
  bn 
  

   depression 
  from 
  which 
  rises 
  the 
  more 
  or 
  less 
  lateral!] 
  ded 
  

  

  posterior 
  wing, 
  — 
  well 
  preserved 
  teeth 
  also 
  showing 
  a 
  slight 
  angula- 
  

   tion 
  on 
  this 
  side 
  of 
  the 
  median 
  lohe 
  where 
  it 
  joins 
  the 
  postei 
  

   depression. 
  

  

  Posterior 
  teeth 
  of 
  the 
  upper 
  jaw 
  suhspatulate 
  in 
  general 
  oir 
  

   terminating 
  posteriorly 
  in 
  an 
  acute 
  angle 
  or 
  spur, 
  anterolateral 
  

   border 
  truncated 
  generally 
  ohliquely 
  outward 
  and 
  backward, 
  Btron 
  

   inrolled 
  along 
  the 
  outer 
  margin 
  for 
  two-thirds 
  the 
  distance 
  from 
  the 
  

   anterior 
  extremity. 
  Crown 
  defined 
  from 
  the 
  base 
  by 
  a 
  shallow 
  in- 
  

   beveled 
  fold 
  along 
  both 
  the 
  antero— 
  and 
  tl 
  ral 
  bord< 
  

   the 
  basal 
  portion 
  in 
  front 
  nearly 
  vertical 
  or 
  somewhat 
  channel 
  

   projecting 
  downward 
  and 
  outward 
  behind 
  where 
  it 
  fori 
  pur 
  

   at 
  the 
  extreme 
  posterior 
  angle. 
  Coronal 
  region 
  Bhowing 
  a 
  de] 
  

   posterior 
  prominence, 
  in 
  front 
  of 
  which 
  less 
  or 
  more 
  ren 
  

   smaller 
  secondary 
  ridge, 
  separated 
  by 
  a 
  plain 
  ing 
  fun 
  

   and 
  having 
  an 
  oblique 
  course 
  bomj/tf 
  within 
  outward 
  in 
  conforn 
  

   with 
  the 
  direction 
  of 
  inrollment; 
  anterior 
  neck 
  th, 
  

   destitute 
  of 
  marked 
  revolving 
  ridges 
  or 
  furrows, 
  and 
  gradual 
  

   traoting 
  toward 
  the 
  truncate 
  anterior 
  border, 
  where 
  the 
  verti 
  

   depth 
  of 
  the 
  tooth 
  is 
  at 
  the 
  minimum, 
  in 
  eonseqi 
  I 
  which 
  I 
  

   anterior 
  border 
  is 
  extremely 
  liable 
  to 
  mutilation 
  | 
  

   rarity 
  of 
  entire 
  examples 
  of 
  this 
  form. 
  

  

  The 
  maxillary 
  posterior 
  form 
  is 
  immediately 
  aucoeeded 
  in 
  froi 
  

   at 
  least 
  one 
  series 
  of 
  teeth, 
  consisting 
  <>f 
  transvi 
  

   which 
  together 
  present 
  a 
  trapezoidal 
  outline, 
  the 
  | 
  

   der 
  articulating 
  with 
  the 
  posterior 
  tooth 
  nearly 
  straight 
  and 
  forming 
  

   a 
  right 
  or 
  obtuse 
  angle 
  with 
  the 
  inner 
  margin, 
  antero-lateral 
  bor 
  

   more 
  or 
  less 
  obliquely 
  converging 
  towards 
  the 
  outward 
  extremty 
  

   coronal 
  rid 
  "f 
  parallel 
  <■ 
  

  

  behind 
  and 
  «• 
  □ 
  ave 
  in 
  front, 
  which 
  in 
  

  

  ■ 
  Mi 
  oharaoters 
  in 
  common 
  with 
  certain 
  for: 
  th. 
  win 
  

  

  i 
  ioualy 
  refern 
  d 
  to 
  ti 
  

   onal 
  Burfaoe 
  presenting 
  the 
  usual 
  enamel 
  rax- 
  

  

  rnotate. 
  

  

  