﻿84 
  PAL/EONTOLOGY 
  OF 
  ILLINOIS. 
  

  

  set 
  punctae; 
  toward 
  the 
  inner 
  margin 
  the 
  enamel 
  layer. 
  is 
  undulated 
  

   hy 
  transverse 
  lines 
  of 
  growth. 
  The 
  absence 
  of 
  distinct 
  longitudinal 
  

   arrangement 
  of 
  the 
  punctffi 
  also 
  contrasts 
  with 
  the 
  above 
  named 
  

   species. 
  A 
  mature 
  individual 
  attains 
  a 
  breadth 
  a 
  khe 
  inner 
  

  

  margin 
  of 
  27 
  mm., 
  and 
  a 
  length 
  along 
  the 
  anterolateral 
  border 
  ol 
  

   probably 
  10.5 
  mm. 
  

  

  We 
  have 
  thus 
  far 
  failed 
  to 
  recognize 
  other 
  and 
  probably 
  associate 
  

   forms 
  of 
  the 
  above 
  species, 
  so 
  that 
  it 
  is 
  impossible 
  to 
  say 
  how 
  in- 
  

   timate 
  its 
  relations 
  are 
  with 
  the 
  teeth 
  that 
  constitute 
  the 
  represent- 
  

   ative 
  forms 
  of 
  the 
  allied 
  genus 
  Stenopterodiu. 
  The 
  general 
  outline 
  

   and 
  the 
  obliquity 
  of 
  the 
  coronal 
  prominence 
  offer 
  striking 
  row 
  m- 
  

   hlances 
  to 
  Deltoptychiiu, 
  but 
  the 
  absence 
  of 
  the 
  secondary 
  lobe 
  

   anterior 
  of 
  the 
  principal 
  prominence 
  precludes 
  its 
  reference 
  to 
  that 
  

   genus. 
  

  

  Geological 
  position 
  and 
  locality: 
  Upper 
  Burlington 
  limestone 
  fish- 
  

   beds; 
  Burlington 
  creek, 
  and 
  Augusta, 
  Iowa. 
  

  

  Vatictnodus? 
  simplex, 
  St. 
  J. 
  and 
  \Y. 
  

  

  Pi. 
  IV, 
  Fik.-. 
  B 
  

  

  Teeth 
  of 
  small 
  size. 
  Maxillary 
  posterior 
  teeth 
  Bubelliptioal 
  in 
  

   outline. 
  Antero-lateral 
  border 
  somewhat 
  obliquely 
  truncated 
  from 
  

   the 
  obtuse 
  inner 
  angle 
  forward 
  to 
  point 
  of 
  inrollment; 
  postero- 
  

   lateral 
  border 
  very 
  rapidly 
  converging 
  from 
  the 
  sharply 
  rounded 
  

   posterior 
  extremity 
  toward 
  point 
  of 
  inrollment, 
  forming, 
  an 
  angle 
  of 
  

   20 
  to 
  :tt) 
  with 
  the 
  opposite 
  border, 
  making 
  a 
  broad 
  | 
  arch; 
  

  

  basal 
  border 
  channeled 
  and 
  posteriorly 
  produced 
  into 
  a 
  thin 
  rim 
  

   which 
  extends 
  beyond 
  the 
  limits 
  of 
  the 
  inbeveled 
  coronal 
  border; 
  

   inner 
  margin 
  in 
  front 
  nearly 
  parallel 
  with 
  the 
  postero-lal 
  

   border, 
  strongly 
  and 
  abruptly 
  arched 
  round 
  the 
  base 
  erf 
  the 
  ooronal 
  

   ridge 
  to 
  the 
  posterior 
  extremity, 
  basal 
  portion 
  relatively 
  deep 
  and 
  

   placed 
  in 
  the 
  same 
  plane 
  as 
  the 
  crown 
  from 
  whioh 
  it 
  is 
  defined 
  by 
  

   the 
  inbeveled 
  inferior 
  bell 
  of 
  enamel. 
  Coronal 
  region 
  model 
  

   arched 
  in 
  the 
  direction 
  of 
  inrollment, 
  posterior 
  lobe 
  occupying 
  

   rather 
  less 
  than 
  half 
  the 
  lateral 
  diameter 
  of 
  the 
  crown. 
  

   oblique, 
  and 
  sufficiently 
  well-defined 
  in 
  front, 
  moderately 
  an 
  

   transversely 
  with 
  a 
  alignl 
  depressed 
  bell 
  along 
  the 
  postero-lal 
  

   border; 
  anterior 
  portion 
  ox 
  neck 
  nearly 
  plain, 
  or 
  vary 
  faintly 
  

  

  • 
  l>-. 
  with 
  an 
  obscure 
  revolving 
  buIcus 
  margined 
  by 
  i 
  

   narrow 
  plain 
  bell 
  along 
  the 
  antero-lateral 
  border, 
  in 
  

  

  ,m 
  tii. 
  posterior 
  lobe 
  is 
  imperfectly 
  defined 
  in 
  front 
  

  

  