﻿VERTEBRATES. 
  89 
  

  

  4^/tion 
  channeled, 
  pooitivoly 
  extended 
  beyond 
  the 
  limits 
  of 
  the 
  narrow 
  

   inbeveled 
  fold 
  of 
  the 
  coronal 
  enamel 
  ; 
  the 
  antero-lateral 
  border 
  simi- 
  

   larly 
  denned. 
  Posterior 
  lobe 
  of 
  the 
  crown 
  gently 
  arched 
  transversely, 
  

   in 
  front 
  merging 
  into 
  the 
  plane 
  anterior 
  surface 
  from 
  which 
  it 
  is 
  

   apparently 
  obscurely 
  defined. 
  Surface, 
  along 
  the 
  inner 
  margin 
  pre- 
  

   serving 
  the 
  dense 
  enamel 
  layer, 
  with 
  distinct 
  lines 
  of 
  growth 
  parallel 
  

   with 
  that 
  margin 
  ; 
  the 
  worn 
  triturating 
  surface 
  showing 
  a 
  minute 
  

   punctate 
  structure, 
  the 
  pores 
  of 
  extreme 
  minuteness 
  and 
  relatively 
  

   widely 
  spaced. 
  Greatest 
  breadth 
  across 
  inner 
  margin 
  9.5 
  m 
  m, 
  the 
  

   basal 
  spur 
  extending 
  a 
  millimeter 
  farther; 
  length 
  along 
  antero-lateral 
  

   border 
  about 
  4.5 
  m 
  m. 
  

  

  Only 
  a 
  solitary 
  example 
  of 
  the 
  present 
  species 
  is 
  known 
  to 
  us. 
  

   The 
  coronal 
  contour, 
  although 
  much 
  worn 
  by 
  use, 
  presents 
  charac. 
  

   teristics 
  consonant 
  with 
  Vaticinodus, 
  specifically 
  differing 
  from 
  its 
  

   Coal 
  Measure 
  congener 
  V. 
  carbonarius, 
  by 
  the 
  relative 
  great 
  diame- 
  

   ter 
  in 
  the 
  direction 
  of 
  inrollment, 
  the 
  broad 
  and 
  uniformly 
  arched 
  

   inner 
  margin, 
  also 
  the 
  more 
  obscure 
  definition 
  of 
  the 
  coronal 
  promi- 
  

   nence. 
  The 
  arched 
  condition 
  of 
  the 
  postero-lateral 
  border, 
  and 
  the 
  

   entirely 
  dissimilar 
  coronal 
  contour 
  distinguishes 
  the 
  tooth 
  from 
  the 
  

   homologous 
  form 
  of 
  Orthopleurodus, 
  with 
  which 
  it 
  is 
  associated 
  in 
  

   the 
  same 
  deposits. 
  

  

  Geological 
  position 
  and 
  locality: 
  Upper 
  Coal 
  Measures 
  ; 
  upper 
  lime- 
  

   stone 
  at 
  LaSalle, 
  111. 
  

  

  Genus 
  DELTOPTYCHIUS, 
  Agassiz. 
  

  

  Delloptychius, 
  Agassiz, 
  MSS., 
  1859, 
  etc., 
  D. 
  {Cochliodus) 
  aeutus, 
  Ag. 
  

  

  Teeth 
  possessing 
  the 
  general 
  characteristics 
  attributable 
  to 
  the 
  

   family 
  Cochliodontidse. 
  

  

  Posterior 
  teeth 
  of 
  the 
  lower 
  jaw 
  trigonal 
  in 
  outline, 
  generally 
  

   strongly 
  built, 
  and 
  moderately 
  arched 
  in 
  the 
  direction 
  of 
  inrollment. 
  

   Antero-lateral 
  border 
  partaking 
  of 
  a 
  slight 
  sigmoidal 
  curvature 
  in 
  

   consonance 
  with 
  the 
  spiral 
  inrollment 
  of 
  the 
  tooth, 
  defined 
  by 
  a 
  

   nearly 
  vertical 
  wall 
  forming 
  at 
  the 
  brink 
  a 
  right 
  angle 
  with 
  the 
  

   superior 
  crown 
  surface, 
  and 
  enveloped 
  to 
  a 
  greater 
  or 
  less 
  extent 
  in 
  

   the 
  coronal 
  enamel 
  which 
  usually 
  constitutes 
  a 
  slight 
  inbeveled 
  fold 
  

   well 
  defined 
  from 
  the 
  basal 
  portion; 
  postero-lateral 
  border 
  more 
  or 
  

   less 
  oblique 
  to 
  the 
  opposite 
  border, 
  toward 
  which 
  it 
  converges 
  at 
  the 
  

   outer 
  extremity, 
  defined 
  above 
  by 
  a 
  shallow 
  enamel 
  fold, 
  beneath 
  

   which 
  the 
  basal 
  rim 
  projects 
  downward 
  and 
  outward, 
  terminating 
  

   posteriorly 
  in 
  a 
  more 
  or 
  less 
  produced 
  spur;, 
  inner 
  margin 
  broadly 
  

  

  