﻿166 
  PALI 
  '.ONTOLOGY 
  OF 
  ILLINOIS 
  

  

  where 
  it 
  is 
  suddenly 
  deflected 
  nearly 
  at 
  right 
  angles 
  to 
  its 
  lon< 
  

   anterior 
  course, 
  gaining 
  the 
  posterior 
  extremity 
  in 
  a 
  slightly 
  o 
  

   course 
  and 
  nearly 
  at 
  right 
  angles 
  to 
  the 
  postero-lateral 
  border. 
  

   Coronal 
  region 
  traversed 
  by 
  a 
  prominent, 
  sharply 
  rounded 
  ridge 
  cul- 
  

   minating 
  a 
  little 
  more 
  than 
  one-third 
  the 
  distance 
  from 
  the 
  pi 
  

   fcerior 
  border, 
  to 
  which 
  the 
  moderately 
  concave 
  slope 
  abruptly 
  de- 
  

   scends, 
  margined 
  by 
  the 
  very 
  narrow 
  alation, 
  the 
  broad 
  anterior 
  

   slope 
  more 
  gradually 
  declining 
  with 
  gentle 
  fcransi 
  mcavity 
  in 
  

  

  the 
  vicinity 
  of 
  the 
  anterolateral 
  border. 
  Surface 
  more 
  or 
  less 
  dis- 
  

   tinctly 
  undulated 
  transversely, 
  the 
  dense 
  enamel 
  layer 
  toward 
  the 
  

   inner 
  margin 
  as 
  also 
  the 
  worn 
  area 
  marked 
  by 
  impressed, 
  irregu- 
  

   larly-spaced 
  lines 
  of 
  growth 
  parallel 
  with 
  the 
  inner 
  margin 
  ; 
  puncta- 
  

   tion 
  line 
  and 
  close. 
  A 
  small 
  perfect 
  tooth 
  measures 
  across 
  the 
  

   inner 
  margin 
  11 
  mm.; 
  length 
  of 
  antero-lateral 
  border 
  to 
  inrolled 
  

   outer 
  margin 
  7 
  mm. 
  

  

  The 
  above 
  description 
  refers 
  to 
  a 
  form 
  of 
  peculiarly 
  masf 
  

   strongly 
  involute 
  teeth 
  of 
  which 
  there 
  are 
  several 
  well-preserved 
  

   examples 
  in 
  the 
  collections 
  before 
  us. 
  In 
  regard 
  to 
  the 
  specific 
  rela- 
  

   tions 
  of 
  these 
  teeth 
  with 
  other 
  known 
  forms, 
  the 
  facts 
  offer 
  little 
  

   beyond 
  conjecture. 
  So 
  far 
  as 
  relates 
  to 
  the 
  superficial 
  coronal 
  

   features 
  they 
  offer 
  no 
  appreciable 
  contrast 
  with 
  Deltodui 
  tpatulatm, 
  

   N. 
  and 
  W.; 
  but 
  the 
  value 
  of 
  these 
  resemblances 
  it 
  is 
  impossible 
  at 
  

   the 
  present 
  time 
  to 
  determine. 
  In 
  the 
  present 
  instance 
  we 
  have 
  no 
  

   evidence 
  such 
  as, 
  in 
  the 
  case 
  of 
  Cochliodui, 
  enables 
  the 
  grouping 
  

   together 
  of 
  divers 
  dental 
  forms 
  with, 
  to 
  say 
  the 
  least, 
  strong 
  i 
  

   sumptive 
  evidence 
  in 
  support 
  of 
  the 
  interpretations 
  relating 
  to 
  their 
  

   probable 
  arrangement 
  upon 
  the 
  jaws. 
  On 
  the 
  contrary, 
  with 
  re-; 
  

   to 
  the 
  detached 
  remains 
  of 
  Ddtodtu 
  and 
  Sandalodus, 
  although 
  

   unquestionably 
  partaking 
  of 
  true 
  oochliodont 
  characteristics, 
  the 
  

   student 
  must 
  It 
  guided 
  by 
  their 
  genera] 
  similitude 
  supplemented 
  by 
  

   oritical 
  familiarity 
  with 
  the 
  external 
  structural 
  features 
  which 
  two 
  

   more 
  species 
  possesses 
  in 
  common, 
  the 
  pen 
  «f 
  which 
  may 
  

  

  l„. 
  inferred 
  from 
  what 
  is 
  Known 
  to 
  occur 
  in 
  CochlitxUu 
  and 
  imme- 
  

   diately 
  allied 
  in 
  order 
  to 
  detect 
  even 
  the 
  possible 
  

   relations 
  of 
  the 
  forms 
  met 
  with. 
  Viewed 
  in 
  this 
  Light 
  the 
  a 
  

   ,„„, 
  ( 
  ,f 
  tin 
  present 
  form 
  with 
  the 
  supposed 
  mandibular 
  p 
  

   teeth 
  of 
  l>rlto,iiis 
  tpatulatui 
  Beams 
  highly 
  improbable. 
  Th< 
  

  

  „..,! 
  Inrollment 
  and 
  the 
  Comparatively 
  narrow, 
  rounded 
  enamel 
  

  

  fold 
  of 
  the 
  artioular 
  border, 
  are 
  not 
  in 
  oonsonanoe 
  with 
  tin 
  

   ponding 
  features 
  of 
  the 
  latter 
  form: 
  benoe 
  it 
  does 
  not 
  displ 
  

   relations 
  of 
  tl»' 
  median 
  form 
  ascribed 
  to 
  that 
  ip 
  

  

  