﻿106 
  PALEONTOLOGY 
  OF 
  ILLINOIS. 
  

  

  The 
  above 
  diagnoses 
  are 
  based 
  upon 
  unique 
  examples 
  in 
  eaofa 
  

   instance, 
  the 
  former 
  preserving 
  scarcely 
  more 
  than 
  the 
  outline 
  and 
  

   the 
  excessively 
  worn 
  superficial 
  contour, 
  the 
  latter 
  showing 
  only 
  the 
  

   central 
  portion 
  of 
  the 
  tooth, 
  the 
  mutilated 
  borders 
  not 
  displaying 
  

   the 
  outline 
  of 
  the 
  tooth. 
  They 
  furnish 
  a 
  singular 
  instance 
  of 
  the 
  

   paucity 
  of 
  certain 
  fish-remains 
  in 
  the 
  collections 
  from 
  a 
  formation 
  

   which 
  h:is 
  yielded 
  rich 
  and 
  varied 
  materials 
  pertaining 
  to 
  allied 
  

   genera. 
  The 
  teeth 
  certainly, 
  so 
  far 
  as 
  it 
  is 
  possible 
  to 
  carry 
  the 
  

   comparison, 
  offer 
  striking 
  resemblance 
  to 
  the 
  corresponding 
  forms 
  

   occurring 
  in 
  the 
  superjacent 
  Warsaw 
  limestone, 
  Stenoptt 
  Eoa- 
  

  

  gatw, 
  in 
  outline, 
  apparently 
  coronal 
  conformation, 
  and 
  the 
  character 
  

   and 
  disposition 
  of 
  the 
  punctffi. 
  We 
  should, 
  therefore, 
  be 
  prepared 
  

   to 
  recognize 
  their 
  specific 
  identity 
  with 
  the 
  latter 
  forms 
  were 
  the 
  

   characters 
  noticed 
  in 
  connection 
  with 
  the 
  sole 
  examples 
  as 
  yet 
  

   known 
  to 
  us 
  from 
  the 
  Keokuk 
  horizon, 
  shown 
  to 
  be 
  persistent 
  and 
  

   normal 
  in 
  even 
  a 
  small 
  suite 
  of 
  perfect 
  specimens. 
  

  

  Geological 
  position 
  and 
  locality 
  : 
  Keokuk 
  limestone, 
  fish-bed 
  ; 
  War- 
  

   saw 
  and 
  Hamilton, 
  Illinois. 
  

  

  Stenopterodus 
  elongatus, 
  St. 
  J. 
  and 
  W. 
  

   PL 
  IV. 
  Fit:, 
  l-u. 
  

  

  Maxillary 
  posterior 
  teeth 
  small, 
  elliptical 
  in 
  outline, 
  considerably 
  

   arched 
  and 
  strongly 
  inrolled 
  along 
  the 
  outer 
  margin. 
  Count 
  

   antero-lateral 
  border 
  nearly 
  at 
  right 
  angles 
  to 
  the 
  transverse 
  axie 
  

   the 
  tooth, 
  opposite 
  border 
  gradually 
  converging 
  from 
  the 
  obtusely- 
  

   pointed 
  extremity 
  toward 
  point 
  of 
  inrollment, 
  neither 
  border 
  

  

  Sufficiently 
  well 
  prcsi 
  rv« 
  1 
  to 
  -how 
  details 
  of 
  enamel 
  fold 
  and 
  ha-al 
  

  

  rim. 
  Coronal 
  prominence 
  relatively 
  very 
  broad, 
  or 
  occupying 
  two- 
  

   thirds 
  the 
  lateral 
  diameter 
  of 
  the 
  tooth, 
  abruptly 
  beveled 
  along 
  the 
  

   postero* 
  lateral 
  border, 
  broadly 
  and 
  regularly 
  arched 
  transversely, 
  

   culminating 
  anteriorly 
  where 
  it 
  is 
  defined 
  by 
  a 
  Blight 
  declivity 
  b 
  

  

  :i 
  \uv 
  oblique 
  course 
  toward 
  the 
  outer 
  extremity; 
  anterior 
  ana 
  

   relatively 
  narrow, 
  quite 
  smooth, 
  plane, 
  and 
  nicely 
  rounded 
  in 
  i 
  

   narrow 
  fold 
  along 
  the 
  border, 
  which 
  is 
  defined 
  by 
  a 
  narrow 
  bu! 
  

  

  from 
  the 
  shallow 
  hasal 
  rim. 
  Coronal 
  BUrfaoe 
  minutely 
  and 
  finely 
  

  

  punctate, 
  the 
  punctffi 
  exhibiting 
  a 
  Bomewhat 
  marked 
  I 
  j 
  to 
  

  

  line. 
  11 
  longitudinal 
  disposition, 
  and 
  in 
  mature 
  examples 
  the 
  enamel 
  

   shows 
  distinci 
  parallel 
  lim 
  iwth 
  following 
  the 
  broadly 
  rounded 
  

  

  curvature 
  Of 
  the 
  inner 
  margin. 
  G 
  diameter 
  of 
  a 
  small- 
  

  

  tooth, 
  1.". 
  mm 
  ;! 
  breadth 
  mar 
  middle, 
  6 
  mm.: 
  

  

  -th 
  mIoii" 
  antero-lateral 
  hord( 
  r. 
  I 
  mm. 
  

  

  