﻿178 
  PALEONTOLOGY 
  OF 
  ILLINOIS. 
  

  

  Xwn.oius 
  siMi'Li.x, 
  St. 
  J. 
  and 
  W. 
  

  

  1*1. 
  VIII, 
  Fig. 
  4, 
  5. 
  

  

  Teeth 
  small, 
  trigonal 
  in 
  outline, 
  rather 
  strongly 
  arched 
  from 
  within 
  

   outward. 
  Antero-lateral 
  border 
  fery 
  slightly 
  curved, 
  presenting, 
  an 
  

   abrupt 
  fact' 
  from 
  the 
  sharp 
  angulation 
  above, 
  and 
  enveloped 
  in 
  a 
  

   ratlur 
  the]) 
  fold 
  of 
  the 
  coronal 
  enamel 
  which 
  is 
  more 
  or 
  less 
  d 
  

   tinctly 
  defined 
  from 
  the 
  deep 
  basal 
  rim; 
  inner 
  margin 
  forming 
  

   nearly 
  a 
  right 
  angle 
  with 
  the 
  anterior 
  border, 
  gently 
  aigmoidal 
  in 
  

   curvature 
  with 
  a 
  shallow 
  concavity 
  in 
  the 
  region 
  of 
  the 
  coronal 
  

   depression; 
  postero-lateral 
  border 
  converging 
  toward 
  point 
  of 
  inroll- 
  

   ment 
  at 
  an 
  angle 
  of 
  -r, 
  to 
  80 
  with 
  the 
  opposite 
  border, 
  coronal 
  

   enamel 
  forming 
  a 
  narrow 
  roundel 
  fold 
  inbeveled 
  to 
  the 
  shallow 
  

   basal 
  rim. 
  Coronal 
  prominence 
  slightly 
  convex 
  transversely, 
  borcU 
  n 
  d 
  

   by 
  the 
  abrupt 
  angulation 
  along 
  the 
  antero-lateral 
  Bide, 
  rather 
  steeply 
  

   sloped 
  posteriorly 
  where 
  it 
  is 
  more 
  or 
  Less 
  distinctly 
  defined 
  bj 
  

   slight 
  angulation, 
  or 
  merges 
  into 
  the 
  broad 
  posterior 
  depression, 
  

   which 
  is 
  bordered 
  by 
  the 
  Bteeply 
  upraised 
  alation. 
  Surface 
  showing 
  

   ordinary 
  punctate 
  structure 
  over 
  the 
  worn 
  anas 
  of 
  the 
  crown, 
  hut 
  

   revealing 
  no 
  distinct 
  arrangement 
  in 
  transverse 
  parallel 
  rows, 
  in 
  

   which 
  respecl 
  these 
  teeth 
  depart 
  most 
  widely 
  from 
  the 
  typical 
  spec 
  

   of 
  the 
  genus. 
  Greatest 
  breadth 
  aero— 
  the 
  inner 
  margin. 
  7.5 
  nun.; 
  

   Length 
  along 
  antero-lateral 
  border. 
  8.6 
  mm. 
  

  

  Mr. 
  Springer's 
  collection 
  contains 
  a 
  single 
  specimen 
  of 
  a 
  long 
  nar- 
  

   row 
  tooti 
  which 
  is 
  BuppoBed 
  to 
  represent 
  the 
  posterior 
  form 
  pertain- 
  

   ing 
  to 
  the 
  upper 
  jaw. 
  In 
  genera] 
  coronal 
  contour 
  it 
  is 
  very 
  like 
  the 
  

   above 
  described 
  form 
  of 
  the 
  mandible, 
  showing 
  the 
  same 
  abrupt 
  

   antero-lateral 
  border, 
  with, 
  however, 
  a 
  relatively 
  narrow 
  enamel 
  

   fold, 
  less 
  steeply 
  upraised 
  alation 
  and 
  more 
  gradually 
  converging 
  

   postero-lateral 
  border, 
  whioh 
  makes 
  an 
  angle 
  of 
  20 
  with 
  th< 
  

  

  ti 
  border. 
  The 
  coronal 
  puncta 
  faint 
  traces 
  of 
  transv< 
  

  

  disposition, 
  in 
  whioh 
  particulars 
  it 
  approaches 
  the 
  typical 
  species 
  of 
  

  

  <im,iiis. 
  Length 
  of 
  tooth 
  along 
  antero-lateral 
  border 
  about 
  l 
  

   nun. 
  ; 
  bn 
  adth 
  at 
  inner 
  margin 
  about 
  7 
  mm. 
  

  

  The 
  forms 
  above 
  described, 
  which 
  were 
  doubtli 
  ted 
  upon 
  

  

  the 
  jaws 
  of 
  the 
  same 
  Bpecies, 
  while 
  thej 
  hold 
  most 
  intimately 
  to 
  the 
  

   outline 
  and 
  coronal 
  contour 
  ascribable 
  to 
  A 
  ted 
  

  

  both 
  by 
  the 
  type 
  X. 
  rtria 
  of 
  the 
  Mountain 
  limestoni 
  

  

  [reland, 
  and 
  the 
  equally 
  typical 
  forms 
  from 
  tl 
  i 
  OarbonifeD 
  

  

  ,,f 
  \ 
  !; 
  offer 
  in 
  contrast 
  the 
  ah-, 
  nee 
  of 
  distinct 
  

  

  [ement 
  of 
  the 
  superficial 
  punota. 
  Bat, 
  as 
  fa 
  mention 
  

  

  

  