﻿168 
  PAL2B0NT0L0GI 
  OF 
  [LLINOK 
  

  

  compared 
  with 
  the 
  relatively 
  thin 
  antero-lateral 
  edge, 
  presenting 
  :i 
  

   deep, 
  slightly 
  channeled, 
  inbeveled 
  belt 
  bordered 
  above 
  by 
  the 
  thick, 
  

   rounded 
  enamel 
  foldj 
  inner 
  margin 
  making 
  an 
  angle 
  of 
  about 
  90 
  with 
  

  

  the 
  anterior 
  articular 
  border 
  to 
  the 
  base 
  oi 
  the 
  coronal 
  ridge, 
  where 
  it 
  

   is 
  abruptly 
  rounded 
  and 
  deflected 
  nearly 
  at 
  right 
  angle 
  to 
  its 
  an! 
  

   rior 
  course 
  with 
  a 
  slight 
  concavity 
  in 
  passing 
  th< 
  ior 
  depn 
  

  

  sion 
  to 
  the 
  subacute 
  posterior 
  angle. 
  Coronal 
  contour 
  Btrongly 
  

   marked 
  by 
  the 
  elevated 
  ridgi 
  which 
  culminates 
  in 
  a 
  rounded 
  ci 
  

   overhanging 
  the 
  deep, 
  narrow 
  posterior 
  depression, 
  the 
  wide 
  anterior 
  

   slope 
  presenting 
  a 
  slight 
  transverse 
  concavity; 
  posterior 
  alation 
  

   forms 
  a 
  rounded 
  Lobe 
  well 
  defined 
  from 
  thi 
  .like 
  posterior 
  

  

  depression. 
  Surface 
  showing 
  more 
  or 
  Less 
  distinct 
  longitudinal 
  pi. 
  

   in 
  the 
  less 
  worn 
  enamel 
  layer 
  toward 
  the 
  inner 
  margin, 
  and 
  travel- 
  

   by 
  transverse 
  lines 
  and 
  faint 
  undulations; 
  punetffl 
  fine, 
  crowd, 
  d. 
  

   showing 
  tendency 
  to 
  conform 
  in 
  their 
  disposition 
  to 
  the 
  trai 
  

   lines. 
  

  

  The 
  collections 
  afford 
  only 
  two 
  examples 
  of 
  the 
  above 
  d< 
  

   form, 
  neither 
  of 
  which 
  are 
  sufficiently 
  perfect 
  to 
  permit 
  aceux 
  

   measurement 
  of 
  their 
  dimensions, 
  although 
  sufficiently 
  so 
  to 
  allow 
  

   satisfactory 
  comparison 
  with 
  allied 
  species. 
  In 
  size 
  and 
  general 
  

   outline 
  it 
  agrees 
  with 
  its 
  predecessor, 
  Deltodoj 
  nvolutus, 
  of 
  the 
  

  

  Upper 
  Burlington 
  limestone, 
  from 
  which 
  it 
  is 
  distinguished 
  

   appreciably 
  more 
  robust 
  build, 
  and 
  especially 
  by 
  the 
  overhanging 
  

   crest 
  of 
  the 
  coronal 
  ridge 
  or 
  the 
  Lnflexed 
  slope 
  descending 
  into 
  the 
  

   narrow 
  post, 
  rior 
  depression, 
  and 
  the 
  distinctly 
  lobed 
  condition 
  of 
  

   the 
  alation. 
  

  

  logical 
  position 
  and 
  locality: 
  Keokuk 
  Limestone; 
  Warsaw, 
  Illi- 
  

   nois. 
  

  

  DbLTODOPSXS 
  '.' 
  9, 
  Si. 
  J. 
  and 
  \Y. 
  

  

  II. 
  

   •h 
  small, 
  Bubtrigonal 
  in 
  outline. 
  Btrongly 
  arched 
  Longitudin 
  

   and 
  very 
  strongly 
  inrolled 
  spirally. 
  Lntero*-lateral 
  border 
  propor- 
  

   tionately 
  Bhort, 
  basal 
  portion 
  channeled 
  and 
  bordered 
  by 
  the 
  thick- 
  

  

  i 
  n, 
  ,i. 
  inbeveh 
  d 
  i 
  name! 
  fold 
  ; 
  postero-lateraJ 
  bordt 
  r 
  rapidly 
  con 
  

   toward 
  oiii.r 
  inrolled 
  margin; 
  inner 
  margin, 
  from 
  the 
  obtuse 
  a 
  

   angle, 
  very 
  obliquely 
  deflected 
  backward 
  In 
  a 
  slightly 
  concave 
  oui 
  

   tore, 
  abruptly 
  rounded 
  at 
  the 
  baw 
  of 
  the 
  coronal 
  ridge, 
  witl 
  

  

  oavity 
  theno 
  >tl 
  ■■ 
  : 
  • 
  oronal 
  ridge 
  prom- 
  

  

  inent, 
  the 
  sharply 
  rounded 
  crest 
  cuhuinatin 
  it 
  the 
  | 
  

  

  