﻿128 
  PALEONTOLOGY 
  OF 
  ILLINOIS 
  

  

  the 
  usual 
  channeled 
  and 
  downward 
  and 
  outward 
  projecting 
  basal 
  

   rim 
  which 
  is 
  coarsely 
  pitted, 
  the 
  border 
  having 
  a 
  course 
  slightly 
  

   oblique 
  outward 
  and 
  forward 
  to 
  the 
  transverse 
  axis 
  of 
  the 
  tooth; 
  

   postero-latcral 
  border 
  converging 
  toward 
  the 
  outer 
  margin 
  at 
  an 
  angle 
  

   of 
  about 
  60 
  , 
  basal 
  portion 
  channeled 
  and 
  somewhat 
  produced 
  be- 
  

   yond 
  the 
  coronal 
  limits 
  towards 
  the 
  posterior 
  extremity; 
  inner 
  mar- 
  

   gin 
  broadly 
  arched 
  round 
  the 
  base 
  of 
  the 
  principal 
  coronal 
  ri.l 
  

   with 
  a 
  short 
  concavity 
  in 
  front 
  and 
  a 
  broader 
  one 
  in 
  passing 
  the 
  

   posterior 
  depression 
  into 
  the 
  alate, 
  subacute 
  angle, 
  worn 
  Bpecimi 
  

   showing 
  the 
  usual 
  inbeveled 
  edge. 
  Anterior 
  belt 
  of 
  orown 
  well-de- 
  

   fined, 
  narrow, 
  slightly 
  convex 
  transversely, 
  the 
  coronal 
  enamel 
  fold- 
  

   ing 
  over 
  the 
  antero-lateral 
  bonier 
  in 
  a 
  narrow 
  inbeveled 
  belt 
  dis- 
  

   tinctly 
  denned 
  from 
  the 
  basal 
  portion; 
  median 
  ridge 
  prominent, 
  

   relatively 
  broad, 
  occupying 
  considerably 
  more 
  than 
  half 
  the 
  trai 
  

   verse 
  diameter 
  of 
  the 
  crown, 
  moderately 
  and 
  regularly 
  arched 
  trans- 
  

   versely 
  and 
  well-delined 
  on 
  either 
  Bide 
  by 
  an 
  obtuse 
  angulation 
  or 
  

   furrow 
  separating 
  it 
  from 
  the 
  anterior 
  belt 
  and 
  the 
  posterior 
  depi 
  

   sion; 
  posterior 
  alation 
  relatively 
  narrow, 
  considerably 
  upraised, 
  

   nearly 
  plan.' 
  transversely, 
  the 
  coronal 
  enamel 
  forming 
  a 
  delicate 
  

   inbeveled 
  fold 
  along 
  the 
  outer 
  edge. 
  Burface 
  minutely 
  punctate, 
  the 
  

   medullary 
  tubes 
  somewhat 
  widely 
  spaced 
  and 
  about 
  thirty 
  OCCUR 
  

   within 
  a 
  Bquare 
  millimetre, 
  and 
  disposed 
  in 
  aeroU-like 
  curves 
  over 
  

   the 
  surface 
  <>i' 
  the 
  tooth. 
  Length 
  of 
  a 
  medium-size 
  tooth 
  along 
  the 
  

   antero-lateral 
  border 
  8 
  mm 
  : 
  breadth 
  between 
  angles 
  ..f 
  inner 
  margin 
  

   L9mm; 
  breadth 
  of 
  median 
  lobe 
  at 
  innei 
  margin 
  8mm; 
  do. 
  of 
  i 
  

   terior 
  alation 
  3 
  mm; 
  do. 
  anterior 
  bell 
  - 
  nun. 
  

  

  Mandibular 
  median 
  form, 
  of 
  which 
  the' 
  collections 
  offer 
  a 
  Bolitary 
  

   imperfect 
  example 
  Bhowing 
  about 
  half 
  the- 
  inner 
  portioned 
  a 
  mature' 
  

   tooth, 
  exhibits 
  a 
  moderately 
  elevated, 
  sub-angular 
  median 
  ridge, 
  a 
  

   narrow 
  concavity 
  bordering 
  the- 
  postero-latera] 
  edge 
  over 
  whioh 
  the 
  

   enamel 
  forms 
  a 
  narrow 
  inbeveled 
  fold 
  distinctly 
  denned 
  from 
  the- 
  

   channeled 
  basal 
  portion: 
  slop,, 
  in 
  front 
  slightly 
  oonoavt 
  I 
  

   on 
  oearing 
  the 
  antero-lateral 
  border, 
  which 
  latter, 
  as 
  also 
  the 
  w 
  

   oblique 
  inner 
  margin, 
  is 
  mutilated 
  and 
  not 
  clearly 
  denned. 
  Suit: 
  

   punotatiorj 
  similar 
  to 
  thai 
  observed 
  in 
  the 
  posterior 
  terminal 
  form. 
  

  

  fcfaxillarj 
  post* 
  'l> 
  rabspatulate 
  in 
  general 
  out! 
  

  

  mrolh'd. 
  antero-lateral 
  bord< 
  tly 
  oblique 
  with 
  a 
  gentle 
  eon- 
  

  

  . 
  -..• 
  curvature 
  outward 
  and 
  forward 
  from 
  the 
  obtuu 
  a 
  

   poetero-lafa 
  ral 
  bord< 
  i 
  div< 
  ' 
  an 
  angle 
  of 
  •:; 
  . 
  mon 
  or 
  l< 
  

  

  with 
  the 
  opposite 
  bordt 
  r, 
  presenting 
  a 
  broad 
  gentl< 
  ourvature 
  between 
  

  

  