﻿1G0 
  PAL.KoNTOLOGY 
  OF 
  ILLINOIS. 
  

  

  marks 
  an 
  unmistakable 
  approach 
  to 
  the 
  coronal 
  condition 
  of 
  certain 
  

   forms 
  mar 
  Cochliodua, 
  e.g. 
  Chitonodut 
  Springeri, 
  etc. 
  Of 
  other 
  dental 
  

   forms 
  which 
  were 
  associated 
  with 
  the 
  above-mentioned 
  teeth 
  <>f 
  the 
  

   mandible 
  and 
  upper 
  jaw, 
  respectively, 
  we 
  are 
  at 
  the 
  present 
  time 
  

   at 
  a 
  loss 
  to 
  determine 
  their 
  character 
  or 
  identity. 
  

  

  Authentic 
  examples 
  of 
  the 
  forme 
  here 
  associated 
  together 
  have 
  

   been 
  derived 
  from 
  the 
  Warsaw, 
  St. 
  Louis 
  and 
  Chester 
  formati< 
  l 
  

   certain 
  forms 
  representing 
  mandibular 
  posterior 
  teeth 
  have 
  a! 
  

   obtained 
  from 
  the 
  Keokuk 
  formation, 
  but 
  their 
  relations 
  with 
  the 
  

   present 
  genus 
  are 
  not 
  a.s 
  satisfactorily 
  shown 
  as 
  in 
  the 
  cast 
  of 
  the 
  

   later 
  introduced 
  forms 
  alluded 
  to. 
  Deltodus 
  angustm, 
  X. 
  and 
  \Y.. 
  of 
  

   the 
  Chester 
  limestone, 
  which 
  was 
  originally 
  described 
  from 
  examples 
  

   of 
  the 
  elongate 
  posterior 
  teeth 
  of 
  the 
  upper 
  jaw. 
  is 
  regarded 
  as 
  a 
  

   typical 
  representative 
  of 
  the 
  present 
  genus. 
  

  

  Through 
  the 
  courtesy 
  of 
  Lord 
  Enniskillen 
  we 
  have 
  had 
  opportunity 
  

   to 
  compare 
  the 
  American 
  forms 
  with 
  sketches 
  of 
  a 
  large 
  "pah. 
  

   from 
  the 
  Carboniferous 
  limestone 
  of 
  Oreton 
  in 
  Shropshire, 
  England, 
  

   which 
  6eems 
  to 
  be 
  congeneric 
  with 
  the 
  teeth 
  above 
  grouped 
  togetl 
  

   and 
  the 
  monarch 
  of 
  its 
  kind. 
  Possessing 
  the 
  same 
  outline 
  and 
  gen- 
  

   eral 
  contour 
  of 
  coronal 
  region 
  attributable 
  to 
  the 
  maxillary 
  posterior 
  

   teeth 
  of 
  DeUodqpsu, 
  the 
  Oreton 
  example 
  is 
  distinguished 
  by 
  its 
  truly 
  

   gigantic 
  proportions, 
  and, 
  perhaps, 
  also 
  by 
  its 
  relatively 
  narrow 
  

  

  teral 
  diameter 
  and 
  the 
  very 
  steep 
  declivity 
  descending 
  to 
  the 
  an- 
  

   terolateral 
  border. 
  The 
  tooth 
  from 
  which 
  the 
  above 
  mentioi 
  

   sketch 
  was 
  made 
  represents 
  the 
  posterior 
  angle 
  of 
  the 
  wing 
  round 
  

   as 
  though 
  from 
  wear. 
  The 
  specimen 
  measures 
  in 
  greatest 
  length 
  

   nearly 
  '.' 
  centimetres, 
  breadth 
  across 
  the 
  inner 
  margin 
  about 
  I 
  cen- 
  

   timetres. 
  

  

  DbLTODOI 
  si- 
  \i 
  riNis. 
  St. 
  .1. 
  ami 
  \\ 
  . 
  

   I. 
  1 
  lg.L 
  

  

  The 
  species 
  b« 
  re 
  alluded 
  to 
  is 
  represented 
  by 
  a 
  solitary 
  example 
  

  

  of 
  the 
  posterior 
  tooth 
  of 
  the 
  mandible. 
  Comparison 
  reveals 
  i. 
  

  

  intimate 
  relationship 
  with 
  the 
  Bpecies 
  occurring 
  in 
  the 
  Bt. 
  L< 
  

   formation, 
  DeUodopti* 
  St. 
  Ludovici. 
  It 
  is 
  oharaol 
  . 
  in 
  

  

  contradistinction 
  to 
  that 
  Bpecies, 
  by 
  the 
  relative] 
  breadth 
  of 
  

  

  the 
  posterior 
  depression 
  and 
  wing 
  expansion, 
  the 
  narrower 
  and 
  dis- 
  

   tinctly 
  transversely 
  di 
  anterior 
  Blope 
  of 
  the 
  coronal 
  promi- 
  

   nence. 
  The 
  c.ronal 
  siirfae, 
  is 
  worn, 
  so 
  that 
  the 
  pumta 
  app 
  

  

  imewhal 
  ooarser 
  and 
  more 
  regular, 
  while 
  the 
  transverse 
  undula- 
  

   tions 
  are 
  very 
  Like 
  what 
  occurs 
  in 
  the 
  latter 
  li 
  from 
  

  

  