﻿140 
  PALAEONTOLOGY 
  OF 
  ILLINni 
  

  

  posterior 
  or 
  principal 
  ridge 
  occupying 
  half 
  the 
  lateral 
  diameter 
  of 
  

   the 
  tooth, 
  rather 
  strongly 
  convex 
  transversely, 
  posterior 
  slope 
  mod- 
  

   e 
  and 
  uniform 
  to 
  the 
  postero-lateral 
  border, 
  opposite 
  sli 
  

   ling 
  with 
  slight 
  concavity 
  into 
  the 
  narrow 
  median 
  depi 
  

   which 
  corresponds 
  in 
  the 
  extreme 
  obliquity 
  to 
  the 
  course 
  of 
  the 
  an- 
  

   terior 
  articular 
  border: 
  anterior 
  ridge 
  culminating 
  in 
  a 
  shar; 
  

   rounded 
  crest, 
  toward 
  the 
  outer 
  margin 
  flanked 
  by 
  th< 
  rti- 
  

  

  oal, 
  concave 
  slope 
  of 
  the 
  median 
  depression, 
  the 
  ! 
  -•■■■■ 
  ■ 
  J>rocLc7e\ 
  

  

  declivity 
  more 
  gently 
  descending 
  to 
  the 
  anter< 
  era! 
  b» 
  i 
  

   which 
  it 
  is 
  slightly 
  depressed, 
  and 
  marked 
  by 
  faint 
  longitudinal 
  un- 
  

   dulations, 
  or 
  sometimes 
  interrupted 
  plica' 
  which 
  obliquely 
  descend 
  

   from 
  near 
  the 
  cresl 
  toward 
  the 
  oblique 
  anterior 
  portion 
  of 
  the 
  inner 
  

   margin. 
  Length 
  of 
  a 
  specimen 
  of 
  ordinary 
  size 
  along 
  the 
  antt 
  

   lateral 
  border 
  about 
  (1 
  mm. 
  ; 
  transverse 
  diameter 
  at 
  the 
  inner 
  margin 
  

   17 
  mm. 
  

  

  Triturating 
  surface 
  finely 
  and 
  closely 
  punctate 
  in 
  both 
  forms 
  men- 
  

   tioned 
  above, 
  presenting 
  the 
  usual 
  variations 
  in 
  accordance 
  with 
  the 
  

   degree 
  of 
  abrasion 
  to 
  which 
  the 
  surface 
  has 
  been 
  subjected. 
  In 
  

   crossing 
  the 
  narrow 
  ridges 
  the 
  puncta 
  often 
  show 
  marked 
  lateral 
  

  

  igation 
  and 
  disposition 
  in 
  parallel 
  row- 
  corresponding 
  in 
  

   to 
  the 
  formative 
  margin, 
  besides 
  the 
  oblique 
  and 
  longitudinal 
  folds 
  

   already 
  mentioned 
  occurring 
  in 
  the 
  anterior 
  -lope 
  of 
  the 
  maxillary 
  

   teeth; 
  and 
  in 
  excessively 
  worn 
  surfaces 
  the 
  medaktf? 
  layer 
  is 
  entirely 
  v&ft. 
  

   removed, 
  exposing 
  to 
  view 
  the 
  dense 
  bom 
  of 
  

  

  lentaJ 
  structure. 
  

   Only 
  a 
  few 
  specimens 
  representing 
  the 
  above 
  described 
  forms 
  ha-. 
  

   been 
  obtained, 
  associated 
  in 
  the 
  same 
  stratum 
  

   of 
  probably 
  specifically 
  identical 
  forms 
  bav< 
  m 
  

  

  other 
  localities 
  in 
  Illinois 
  and 
  Kansas. 
  Th< 
  

  

  lily 
  distinguishing 
  it 
  from 
  allied 
  earlier 
  appearing 
  form-: 
  the 
  

  

  linally 
  ridged 
  median 
  depression 
  and 
  relatival] 
  narrow 
  a! 
  

   lansion 
  of 
  the 
  mandibular 
  terminal 
  teeth, 
  and 
  the 
  relatn 
  

   porl 
  ual 
  prominences 
  and 
  the 
  peculiar 
  ondulati 
  

  

  the 
  ant 
  ipe 
  in 
  the 
  m:i\r 
  titute 
  U 
  

  

  tures 
  contr 
  ith 
  /'. 
  I 
  

  

  III., 
  and 
  ii 
  obtains 
  d 
  from 
  i 
  

  

  : 
  i 
  • 
  I 
  

  

  Mr. 
  in 
  tin 
  i 
  of 
  shall 
  a 
  of 
  

  

  at 
  Carlinville, 
  I 
  

  

  