﻿L58 
  PALEONTOLOGY 
  OF 
  ILLINOIS 
  

  

  The 
  above 
  diagnoses 
  are 
  based 
  upon 
  examples 
  of 
  the 
  mandibular, 
  

   posterior 
  ami 
  median 
  forms, 
  and 
  the 
  posterior 
  form 
  of 
  the 
  upper 
  

   jaw, 
  derived 
  from 
  lower 
  Coal 
  Measure 
  strata 
  of 
  Illinois. 
  The 
  

   is 
  intimately 
  allied 
  to 
  that 
  occurring 
  in 
  the 
  Chester 
  formation. 
  /><f- 
  

   todus 
  cingulaius, 
  N. 
  and 
  \V. 
  The 
  mandibular 
  terminal 
  form, 
  how- 
  

   ever, 
  is 
  distinguishable 
  by 
  its 
  stouter 
  proportions, 
  wider 
  coronal 
  

   ridge, 
  and 
  relatively 
  shorter 
  longitudinal 
  diameter. 
  The 
  opposed 
  

   teeth 
  of 
  the 
  upper 
  jaw, 
  again, 
  differ 
  from 
  the 
  corresponding 
  Chester 
  

   form 
  in 
  the 
  more 
  prominently 
  transversely 
  arched 
  alation, 
  in 
  which 
  

   particular 
  it 
  hears 
  closer 
  resemblance 
  to 
  1>. 
  undulatu*, 
  N. 
  and 
  W., 
  

   of 
  the 
  Keokuk 
  limestone, 
  from 
  which, 
  however, 
  it 
  widely 
  differs 
  in 
  

   the 
  more 
  angularly 
  rounded 
  contour 
  and 
  concave 
  posterior 
  slope 
  of 
  

   the 
  principal 
  coronal 
  prominence. 
  The 
  Coal 
  Measure 
  forms 
  of 
  the 
  

   Upper 
  Mississippi 
  region, 
  therefore, 
  constitute 
  a 
  well 
  defined 
  spec 
  

   as 
  distinguished 
  from 
  the 
  several 
  specific 
  groups 
  occurring 
  in 
  the 
  

   various 
  formations 
  of 
  the 
  Lower 
  Carboniferous 
  groups 
  in 
  the 
  same 
  

   region. 
  Its 
  intimate 
  resemblance 
  to 
  the 
  species 
  described 
  from 
  the 
  

   (probably) 
  Coal 
  Measure 
  limestone 
  of 
  the 
  Far 
  West, 
  /'. 
  PoweUii, 
  

   has 
  already 
  been 
  remarked 
  upon. 
  It 
  is 
  possible 
  that 
  a 
  larger 
  b 
  

   of 
  specimens 
  of 
  the 
  latter 
  species 
  might 
  prove 
  its 
  specific 
  identity 
  

   with 
  the 
  present 
  teeth; 
  but 
  this 
  can 
  only 
  be 
  demonstrated 
  by 
  the 
  

   comparison 
  of 
  all 
  the 
  forms. 
  

  

  Geological 
  position 
  and 
  localities: 
  The 
  first 
  example 
  of 
  the 
  \n< 
  

  

  species 
  that 
  was 
  brought 
  to 
  our 
  notice, 
  several 
  yean 
  ago, 
  was 
  dis- 
  

   covered 
  by 
  Mr. 
  L. 
  A. 
  fuller 
  in 
  the 
  shales 
  overlying 
  Coal 
  N 
  

   Danville. 
  Subsequently, 
  Mr. 
  Alexander 
  Butters 
  obtained 
  from 
  Un- 
  

   roof 
  shales 
  of 
  Coal 
  No. 
  5, 
  at 
  Carlinville, 
  representatives 
  of 
  all 
  thi 
  

   of 
  the 
  forms 
  thus 
  far 
  identified 
  as 
  pertaining 
  to 
  this 
  spei 
  

  

  (iiM 
  s 
  DELTODOPSIS,* 
  Bt 
  J. 
  and 
  w. 
  

  

  •li 
  possessing 
  coronal 
  contour 
  and 
  general 
  aspeci 
  1 
  < 
  dus. 
  

  

  Mandibular 
  posterior 
  teeth 
  distinguished 
  by 
  their 
  oblique 
  Bub-tri- 
  

   ; 
  1 
  1 
  1 
  • 
  ■ 
  1 
  1 
  1 
  .• 
  i 
  r 
  outline 
  and 
  the 
  remarkable 
  obliquity 
  of 
  the 
  anterior 
  portion 
  

   of 
  the 
  inner 
  margin, 
  proportionately 
  short 
  extent 
  of 
  the 
  am 
  

   articular 
  border, 
  the 
  sometimes 
  longitudinally 
  de] 
  oondition 
  

  

  of 
  the 
  anterior 
  slope 
  of 
  the 
  coronal 
  prominence, 
  and 
  the 
  tendency 
  

   mon 
  or 
  Less 
  well 
  defined 
  median 
  ridge 
  al< 
  mm- 
  

  

  

  