﻿182 
  rA!..K()NTOLOGY 
  OF 
  LLLINO] 
  

  

  •ies 
  represented 
  by 
  the 
  present 
  form 
  would 
  then 
  have 
  to 
  he 
  re- 
  

   legated 
  to 
  Chitonodtu. 
  

  

  logical 
  position 
  and 
  locality: 
  Warsaw 
  lim 
  near 
  the 
  mouth 
  

  

  of 
  Piasa 
  creek, 
  ahove 
  Alton, 
  111. 
  

  

  PcBCHiODUB 
  St. 
  Ludovioi, 
  St. 
  J. 
  and 
  W. 
  

   PL 
  viii. 
  Big. 
  i, 
  is. 
  

  

  ih 
  of 
  small 
  size, 
  representing 
  the 
  posterior 
  forme 
  of 
  the 
  upper 
  

   and 
  lower 
  jaws 
  ; 
  dental 
  armament 
  of 
  the 
  anterior 
  portions 
  of 
  the 
  

   jaws 
  unknown. 
  

  

  Mandibular 
  posterior 
  teeth 
  strongly 
  arched 
  in 
  the 
  direction 
  of 
  in- 
  

   rollment, 
  in 
  outline 
  presenting 
  the 
  usual 
  subspatulate 
  form. 
  Antero- 
  

   lateral 
  border 
  relatively 
  very 
  short, 
  forming 
  nearly 
  a 
  righl 
  

   with 
  a 
  line 
  connecting 
  the 
  angles 
  of 
  the 
  inner 
  margin, 
  extremely 
  

   attenuated 
  and 
  contracted 
  from 
  the 
  anterior 
  coronal 
  ridgi 
  : 
  1 
  

   lateral 
  border 
  converging 
  toward 
  point 
  of 
  ihrollmenf 
  at 
  an 
  angle 
  of 
  

   50°, 
  more 
  or 
  less, 
  with 
  the 
  opposite 
  border, 
  basal 
  portion 
  de< 
  

   channeled 
  and 
  widely 
  expanded 
  beyond 
  the 
  coronal 
  lim 
  I 
  

   orly, 
  terminating 
  in 
  the 
  acutely 
  rounded 
  spur 
  of 
  the 
  posterior 
  

   tremity 
  ; 
  inner 
  margin 
  making 
  a 
  deep 
  tegular 
  concavity 
  in 
  the 
  

   region 
  of 
  the 
  posterior 
  depression, 
  broadly 
  arched 
  round 
  the 
  1 
  

   of 
  the 
  median 
  lobe, 
  with 
  a 
  shallow 
  concavity 
  in 
  the 
  intermediate 
  

   depression 
  in 
  front, 
  and 
  angularly 
  arched 
  round 
  the 
  anterior 
  rid 
  

   beyond 
  which 
  the 
  course 
  is 
  suddenly 
  and 
  very 
  obliquely 
  deflected 
  

   forward 
  to 
  the 
  obtuse 
  anterior 
  angle. 
  The 
  coronal 
  region 
  i^ 
  Btroi 
  

   marked 
  by 
  the 
  characteristic 
  contour 
  features. 
  Anterior 
  lol 
  

   row, 
  prominent, 
  culminating 
  in 
  a 
  rounded 
  crest 
  moderately 
  oblique 
  

   to 
  the 
  antero-lateral 
  border, 
  in 
  front 
  -*4- 
  the 
  abrupt 
  slightly 
  con 
  

   Blope/ 
  descending 
  to 
  the 
  coronal 
  limits, 
  where 
  it 
  is 
  bordered 
  bj 
  a 
  

   narrow 
  slightly 
  depressed 
  belt, 
  beyond 
  which 
  the 
  basal 
  portion 
  ; 
  

   jeote 
  as 
  a 
  wide, 
  rapidly 
  narrowing 
  apron 
  to 
  the 
  anterior 
  e: 
  

   of 
  the 
  tooth; 
  posterior 
  slope 
  equally 
  ahn.pt 
  hut 
  of 
  

   t. 
  nt 
  ; 
  intermediate 
  depression 
  equalin 
  Ith 
  of 
  | 
  

  

  lobe, 
  in 
  perfect 
  teeth 
  showing 
  a 
  nearly 
  plan, 
  area 
  narrowing 
  from 
  

   within 
  outward, 
  defined 
  from 
  the 
  bordering 
  elei 
  y 
  a 
  si 
  

  

  angulation 
  on 
  either 
  Bide, 
  in 
  worn 
  and 
  mature 
  examples 
  the 
  depi 
  

  

  ,ii 
  pn 
  -, 
  ots 
  a 
  mon 
  alar 
  transvi 
  

  

  median 
  or 
  principal 
  lobe 
  rituafa 
  a 
  littl< 
  ior 
  of 
  tin 
  

  

  line. 
  I. 
  madly 
  and 
  i. 
  ulaily 
  an 
  lied 
  tran>\. 
  i>. 
  ly. 
  the 
  abrupt 
  and 
  

  

  1,,, 
  d 
  which 
  

  

  