﻿VEETEBEATES. 
  217 
  

  

  tubes 
  are 
  raised 
  into 
  crater-like 
  prominences 
  encircled 
  by 
  delicate 
  

   radi, 
  giving 
  to 
  tbe 
  surface 
  a 
  beautiful 
  stellate 
  ornamentation 
  very 
  

   like 
  tbat 
  so 
  commonly 
  met 
  with 
  in 
  the 
  teeth 
  of 
  Cochliodonts. 
  The 
  

   general 
  outline 
  agrees 
  with 
  that 
  of 
  typical 
  examples, 
  the 
  posterior 
  

   margin 
  in 
  the 
  worn 
  condition 
  conforming 
  to 
  the 
  bands 
  of 
  growth 
  ; 
  

   but 
  the 
  coronal 
  contour 
  shows 
  a 
  greater 
  fullness 
  in 
  the 
  inner 
  half, 
  

   in 
  which 
  particular 
  it 
  bears 
  greater 
  resemblance 
  to 
  the 
  Chester 
  

   species 
  Psammodus 
  angularis, 
  N. 
  and 
  W. 
  However, 
  similarly 
  pre- 
  

   served, 
  examples 
  from 
  Alton 
  show 
  a 
  less 
  regular 
  concavity 
  in 
  the 
  

   transverse 
  profile 
  and 
  corresponding 
  fullness 
  in 
  the 
  inner 
  half, 
  ap- 
  

   proximating 
  the 
  conditions 
  observable 
  in 
  the 
  Michigan 
  example. 
  It 
  

   is 
  much 
  to 
  be 
  desired 
  that 
  larger 
  materials 
  from 
  the 
  latter 
  quarter 
  

   be 
  obtained, 
  in 
  order 
  to 
  trace 
  more 
  definitely 
  the 
  characteristics 
  of 
  

   its 
  piscine 
  fauna 
  and 
  its 
  relations 
  to 
  that 
  of 
  the 
  southern 
  and. 
  south- 
  

   western 
  areas 
  of 
  the 
  same 
  deposits. 
  

  

  The 
  maxillary 
  tooth 
  bears 
  somewhat 
  marked, 
  resemblance 
  to 
  the 
  

   same 
  form 
  of 
  teeth 
  occurring 
  in 
  the 
  Upper 
  Burlington 
  limestone, 
  

   Psammodus 
  Lovianus, 
  but 
  the 
  associate 
  mandibular 
  teeth 
  are 
  quite 
  

   different 
  from 
  those 
  identified 
  with 
  the 
  latter 
  species, 
  as 
  will 
  be 
  

   manifest 
  on 
  comparison 
  of 
  the 
  illustrations 
  given 
  of 
  the 
  two 
  species. 
  

   We 
  regret 
  the 
  lack 
  of 
  material 
  permitting 
  detail 
  comparison 
  with 
  

   the 
  European 
  species 
  P.porosxis, 
  Agass., 
  although 
  little 
  doubt 
  is 
  

   entertained 
  respecting 
  the 
  specific 
  distinctness 
  of 
  the 
  above 
  described 
  

   forms. 
  

  

  Geological 
  position 
  and 
  localities: 
  Not 
  uncommon 
  in 
  the 
  St. 
  Louis 
  

   limestone 
  ; 
  St. 
  Louis, 
  Mo., 
  Alton, 
  and 
  Monroe 
  Co., 
  111., 
  Grand 
  Eapids, 
  

   Michigan. 
  

  

  Psammodus 
  oelatus, 
  St. 
  J. 
  and 
  W. 
  

  

  PI. 
  XVIII, 
  Fig. 
  1. 
  

  

  A 
  fragment 
  of 
  a 
  small 
  tooth 
  from 
  the 
  St. 
  Louis 
  formation 
  at 
  

   Pella, 
  offers 
  so 
  well-marked 
  peculiarities 
  that 
  we 
  have 
  decided 
  to 
  

   notice 
  it 
  under 
  the 
  above 
  designation. 
  It 
  is 
  homologous 
  with 
  the 
  

   form 
  elsewhere 
  referred 
  to 
  the 
  upper 
  jaw, 
  and. 
  is 
  distinguished 
  from 
  

   Psammodus 
  plemis, 
  of 
  the 
  same 
  formation, 
  by 
  the 
  concavity 
  in 
  the 
  

   curvature 
  of 
  the 
  outer 
  border, 
  the 
  strongly 
  produced 
  postero-outer 
  

   angle, 
  more 
  strongly 
  inbeveled 
  anterior 
  basal 
  wall, 
  and 
  the 
  rugation 
  

   of 
  the 
  coronal 
  surface, 
  which 
  presents 
  a 
  very 
  moderate 
  longitudinal 
  

   convexity 
  and 
  transversely 
  depressed, 
  contour. 
  The 
  length 
  of 
  the 
  

   tooth 
  along 
  the 
  outer 
  border 
  between 
  the 
  acute 
  posterior 
  and 
  the 
  

  

  