﻿VEETEBEATES. 
  75 
  

  

  can 
  scarcely 
  be 
  questioned. 
  Its 
  salient 
  contrasts, 
  compared 
  with 
  

   the 
  forms 
  associated 
  under 
  the 
  latter 
  specific 
  designation, 
  consist 
  in 
  

   the 
  more 
  symmetrical 
  outline, 
  and 
  coarser, 
  irregular 
  character 
  of 
  

   the 
  coronal 
  punetae. 
  

  

  Geological 
  position 
  and 
  locality: 
  Chester 
  limestone 
  ; 
  Chester, 
  Illinois. 
  

  

  Genus 
  T^ENIODUS, 
  L. 
  de 
  Koninck 
  Mss. 
  

  

  Teeth 
  representing 
  the 
  posterior 
  form 
  of 
  the 
  upper 
  jaw 
  attain 
  large 
  

   size, 
  sub-rhomboidal 
  or 
  oblique-trapezoidal 
  in 
  outline, 
  moderately 
  

   arched 
  from 
  within 
  outward, 
  and 
  inrolled, 
  more 
  or 
  less 
  obliquely, 
  

   outward 
  and 
  forward. 
  Lateral 
  borders 
  regularly 
  and 
  gradually 
  con- 
  

   verging 
  toward 
  the 
  outer 
  extremity, 
  which 
  may 
  be 
  truncate, 
  as 
  in 
  

   Psephodus, 
  of 
  moderate 
  depth, 
  inferior 
  or 
  basal 
  portion 
  channeled 
  

   and 
  distinctly 
  defined 
  from 
  the 
  coronal 
  fold, 
  which 
  forms 
  a 
  sort 
  of 
  

   coping 
  along 
  the 
  upper 
  edge 
  ; 
  antero-lateral 
  border 
  relatively 
  short, 
  

   having 
  a 
  more 
  or 
  less 
  oblique 
  outward 
  and 
  forward 
  course 
  and 
  slightly 
  

   concave 
  curvature 
  between 
  the 
  obtuse 
  inner 
  angle 
  and 
  point 
  of 
  inroll- 
  

   ment 
  ; 
  postero-lateral 
  border 
  gently 
  and 
  regularly 
  arched 
  from 
  the 
  sub- 
  

   acute 
  posterior 
  angle, 
  and 
  gradually 
  converging 
  outward 
  with 
  slightly 
  

   greater 
  obliquity 
  than 
  the 
  opposite 
  border 
  ; 
  inner 
  margin 
  making 
  a 
  

   gentle 
  'curvature 
  from 
  the 
  posterior 
  angle 
  forward 
  to 
  the 
  rounded 
  

   angle 
  at 
  the 
  base 
  of 
  the 
  coronal 
  prominence, 
  where 
  it 
  is 
  suddenly 
  

   deflected 
  forward 
  with 
  a 
  slight 
  concavity 
  to 
  the 
  anterior 
  angle, 
  

   making 
  a 
  very 
  obtuse 
  angle 
  with 
  the 
  posterior 
  half 
  of 
  its 
  course. 
  

   Coronal 
  contour 
  presenting 
  a 
  simple 
  posterior 
  prominence 
  culmin- 
  

   ating 
  in 
  a 
  low, 
  rounded 
  crest, 
  the 
  broad 
  posterior 
  slope 
  usually 
  

   slightly 
  convex, 
  though 
  sometimes 
  faintly 
  depressed, 
  that 
  on 
  the 
  

   opposite 
  side 
  apparently 
  more 
  abrupt 
  and 
  merging 
  into 
  the 
  slightly 
  

   depressed 
  anterior 
  area 
  ; 
  the 
  surface 
  is 
  more 
  or 
  less 
  distinctly 
  un- 
  

   dulated 
  by 
  transverse 
  ridges 
  separated 
  by 
  narrow 
  furrows, 
  conform- 
  

   ing 
  in 
  outline 
  to 
  the 
  inner 
  margin. 
  The 
  usual 
  punctate 
  structure 
  

   occurs 
  over 
  the 
  entire 
  coronal 
  region, 
  the 
  pores 
  showing 
  a 
  tendency 
  

   to 
  irregular 
  elongation 
  in 
  the 
  axis 
  of 
  the 
  transverse 
  sulci. 
  Inferior 
  

   surface 
  of 
  teeth 
  showing 
  the 
  dense 
  inferior 
  layer 
  longitudinally 
  

   striated; 
  thickest 
  beneath 
  the 
  coronal 
  ridge. 
  

  

  The 
  foregoing 
  diagnosis 
  applies 
  to 
  a 
  group 
  of 
  teeth 
  meagerly 
  rep- 
  

   resented 
  in 
  the 
  collections 
  by 
  the 
  form 
  homologous 
  with 
  the 
  posterior 
  

   teeth 
  of 
  the 
  upper 
  jaws 
  of 
  Cochliodus 
  and 
  allied 
  genera. 
  A 
  single, 
  

   nearly 
  perfect 
  specimen 
  from 
  the 
  Carboniferous 
  limestone 
  of 
  J$*dv, 
  

  

  