﻿VEBTEBBATES. 
  147 
  

  

  prominence 
  relatively 
  narrow, 
  culminating 
  about 
  midway 
  of 
  the 
  an- 
  

   terior 
  half 
  of 
  the 
  coronal 
  region, 
  abruptly 
  descending 
  to 
  the 
  antero- 
  

   lateral 
  border, 
  gently 
  sloping 
  into 
  the 
  broad, 
  shallow 
  posterior 
  

   depression, 
  which 
  together 
  with 
  the 
  slightly 
  upraised 
  wing 
  occupies 
  

   a 
  proportionately 
  wide 
  extent 
  of 
  the 
  coronal 
  area. 
  Surface 
  marked 
  

   by 
  sub-equal 
  and 
  more 
  or 
  less 
  parallel 
  transverse 
  folds, 
  separated 
  

   by 
  narrow 
  furrows 
  similar 
  to 
  the 
  opposed 
  mandibular 
  teeth, 
  and 
  

   conforming 
  to 
  the 
  curvature 
  of 
  the 
  inner 
  margin. 
  A 
  medium 
  size 
  

   tooth 
  measures 
  in 
  greatest 
  transverse 
  diameter 
  at 
  the 
  inner 
  margin 
  

   about 
  11.5 
  mm; 
  greatest 
  length 
  from 
  posterior 
  angle 
  to 
  outer 
  in- 
  

   rolled 
  margin, 
  about 
  16 
  mm. 
  

  

  The 
  species 
  above 
  noticed 
  is 
  closely 
  allied 
  to 
  its 
  congeners 
  of 
  the 
  

   Deltodus 
  undulatus 
  type. 
  The 
  mandibular 
  posterior 
  teeth 
  are, 
  how- 
  

   ever, 
  distinguishable 
  by 
  their 
  relative 
  great 
  breadth 
  at 
  the 
  inner 
  

   margin, 
  as 
  compared 
  to 
  the 
  length; 
  the 
  narrow 
  wing 
  expansion 
  re- 
  

   calls 
  more 
  the 
  condition 
  prevalent 
  in 
  D. 
  occidentalis, 
  from 
  whicb, 
  

   however, 
  it 
  may 
  be 
  recognized 
  by 
  its 
  broader, 
  shorter 
  form 
  and 
  

   undulated 
  coronal 
  surface. 
  The 
  opposed 
  maxillary 
  teeth 
  bear 
  a 
  

   striking 
  resemblance 
  to 
  D. 
  cingulatus, 
  N. 
  and 
  W., 
  of 
  the 
  Chester 
  

   limestone, 
  differing, 
  however, 
  in 
  the 
  greater 
  obliquity 
  of 
  the 
  inner 
  

   margin 
  and, 
  perhaps, 
  the 
  more 
  numerous 
  transverse 
  sulci, 
  producing 
  

   the 
  banded 
  appearance 
  of 
  the 
  crown 
  surface, 
  while 
  the 
  more 
  widely 
  

   expanded 
  wing, 
  and 
  the 
  greater 
  obliquity 
  of 
  the 
  inner 
  margin, 
  also 
  

   serve 
  to 
  distinguish 
  them 
  from 
  D. 
  undulatus, 
  N. 
  and 
  W. 
  ; 
  also, 
  in 
  

   both 
  forms 
  of 
  the 
  present 
  species 
  the 
  punctse 
  are 
  perceptibly 
  more 
  

   crowded 
  than 
  is 
  the 
  case 
  in 
  D. 
  cingulatus, 
  and 
  in 
  which 
  respect 
  they 
  

   again 
  resemble 
  D. 
  undulatus. 
  

  

  As 
  yet 
  the 
  collections 
  contain 
  very 
  few 
  examples 
  of 
  the 
  teeth 
  above 
  

   referred 
  to, 
  but 
  these, 
  besides 
  their 
  small 
  size, 
  offer 
  characters 
  which 
  

   seem 
  to 
  authorize 
  the 
  recognition 
  of 
  their 
  distinct 
  specific 
  standing, 
  

   although 
  closely 
  allied 
  to 
  the 
  species 
  with 
  which 
  they 
  have 
  been 
  

   compared. 
  

  

  Geological 
  position 
  and 
  localities 
  : 
  Warsaw 
  beds 
  : 
  Barrett's 
  Station, 
  

   St. 
  Louis 
  Co., 
  Mo. 
  ; 
  Madison 
  county, 
  Piasa 
  creek 
  above 
  Alton, 
  and 
  

   Scott 
  county, 
  111. 
  

  

  