﻿98 
  PALEONTOLOGY 
  OF 
  ELLINOIS. 
  

  

  Deltoptvchius 
  bxpansus, 
  St. 
  J. 
  and 
  W. 
  

  

  PL 
  V. 
  lit:. 
  '.'. 
  18. 
  

  

  Posterior 
  teeth 
  of 
  the 
  mandibles, 
  trigonal 
  in 
  general 
  outline, 
  outer 
  

   extremity 
  strongly 
  inrolled, 
  relatively 
  broadly 
  expanded 
  posteriorly, 
  

   and 
  broadly 
  arched 
  along 
  the 
  inner 
  margin 
  with 
  sigmoidal 
  curvature 
  

   in 
  passing 
  to 
  the 
  posterior 
  extremity 
  of 
  the 
  Btrong 
  win- 
  expansion, 
  

   antero-lateral 
  border 
  slightly 
  curved 
  Bigmoidally, 
  moderately 
  deep, 
  

   the 
  greater 
  portion 
  of 
  the 
  vertical 
  Car. 
  I. 
  eing 
  covered 
  by 
  the 
  coronal 
  

   enamel 
  and 
  making 
  a 
  well-defined 
  angulation 
  above; 
  posterolateral 
  

   border 
  rapidly 
  converging 
  toward 
  the 
  extremity, 
  basal 
  portion 
  pro- 
  

   jecting 
  somewhat 
  beyond 
  the 
  narrow 
  and 
  prominent 
  fold 
  limiting 
  

   the 
  coronal 
  surface, 
  and 
  more 
  or 
  less 
  produced 
  posteriorly. 
  Coronal 
  

   surface 
  showing 
  a 
  broad, 
  deep 
  posterior 
  depression, 
  which, 
  together 
  

   with 
  the 
  alate 
  border, 
  constitutes 
  half 
  the 
  lateral 
  diameter 
  of 
  the 
  

   tooth; 
  median 
  lobe 
  relatively 
  narrow, 
  generally 
  obscurely 
  defined 
  in 
  

   front 
  'from 
  the 
  narrow 
  anterior 
  plane 
  belt 
  with 
  which 
  it 
  is 
  usually 
  

   merged 
  over 
  the 
  greater 
  extent 
  of 
  the 
  outer 
  surface. 
  Length 
  of 
  a 
  

   medium-size 
  tooth 
  along 
  anterolateral 
  border 
  8 
  mm.; 
  breadth 
  at 
  

   inner 
  margin 
  8.5 
  mm. 
  

  

  Posterior 
  tooth 
  of 
  the 
  upper 
  jaw 
  in 
  outline 
  spatulate. 
  terminating 
  

   posteriorly 
  in 
  an 
  eccentric 
  sharply 
  rounded 
  spur, 
  antero-lateral 
  bor- 
  

   der 
  obliquely 
  truncated 
  from 
  inner 
  angle 
  outward 
  and 
  forward. 
  I 
  

   onal 
  prominence 
  comprising 
  marly 
  two-thirds 
  the 
  transverse 
  diarn. 
  

   of 
  the 
  tooth, 
  posterior 
  lobe 
  moderately 
  convex 
  transversely, 
  sal 
  

   dinate 
  Lobe 
  relatively 
  broad 
  and 
  prominent, 
  anterior 
  area 
  Bmooth, 
  

   and 
  narrowed 
  toward 
  the 
  antero-lateral 
  border. 
  Burfaee 
  minutely 
  

   and 
  closely 
  punctate, 
  in 
  the 
  Bame 
  manner 
  observed 
  in 
  the 
  opp 
  

   teeth. 
  Greatesi 
  transverse 
  diameter 
  of 
  a 
  medium-size 
  tooth 
  about 
  

  

  L2 
  nun.: 
  greatest 
  diagonal 
  breadth 
  across 
  the 
  posterior 
  prominei 
  

   5 
  nun.: 
  length 
  along 
  antero-lateral 
  border 
  1.6 
  to 
  5 
  nun. 
  

  

  oi 
  other 
  dental 
  forms 
  occurring 
  with 
  the 
  above 
  described 
  teeth, 
  

   none 
  have 
  been 
  recognised 
  as 
  probably 
  Bpecifioally 
  identical. 
  En 
  

   superficial 
  coronal 
  characters, 
  aa 
  the 
  punctation 
  and 
  appeal 
  

   the 
  enamel 
  layer, 
  the 
  two 
  forms 
  above 
  noticed 
  possess 
  most 
  inti- 
  

   mate 
  characters 
  in 
  common, 
  so 
  that, 
  notwithstanding 
  the 
  fart 
  that 
  

   :i 
  „ 
  Ill( 
  , 
  material 
  in 
  our 
  possession 
  consists 
  of 
  Isolated 
  teeth, 
  Little 
  

   doubl 
  is 
  entertained 
  as 
  to 
  their 
  h. 
  instituted 
  parts 
  of 
  the 
  

  

  dentition 
  of 
  the 
  Bame 
  

  

  apared 
  with 
  the 
  Keokul 
  . 
  /'• 
  WachimUhi, 
  the 
  pn 
  

  

  th 
  present 
  well-marked 
  differed 
  ihthen 
  

  

  